Category: Chemistry Notes PPT

Aluminium hydroxide is an inorganic compound made up of aluminium ion and hydroxide ions. It is an amphoteric compound which means it can act as an acid as well as a base. Aluminium hydroxide minerals occur in nature. It holds the property of an antacid. The IUPAC name of the aluminium hydroxide is Aluminium trioxide.

Hydrophobicity is a property of aluminium hydroxide. In most cases, it produces lyophobic solutions. The hydrolysis of aluminium chloride can be used to prepare aluminium hydroxide gels.

3H₂O + AlCl₃ Al(OH)₃ + 3HCl

Aluminium Compounds

Aluminium is an inorganic element belonging to the thirteenth group. Aluminium reacts with nitrogen gas and forms an aluminium nitride

Al + N₂ → AlN

Aluminium reacts with the oxygen gas and forms aluminium trioxide also known as alumina.

Al + O₂ → Al₂O₃

Aluminium reacts with hydrochloric acid and forms aluminium trichloride as a product and hydrogen gas as a byproduct. This aluminium trichloride is used in the preparation of aluminium hydroxide gels. 

Al + HCl → AlCl₃ + H₂

Aluminium reacts with the dilute sodium hydroxide solution and forms aluminium trihydroxide. This molecule is amphoteric in nature. Therefore, it further reacts with the dilute sodium hydroxide solution and forms sodium meta illuminate aa a product and hydrogen gas as a byproduct. 

Al + NaOH (dil) → Al(OH)₃ → Na[Al(OH)₄] + H₂

Aluminium hydroxide reacts with the water molecules and forms a solution. This reaction can be used to clear drains. This reaction is also used to remove the obstructions from the drainage pipe.

AlCl₃ + H₂O → [Al (H₂O)₆]⁺³ + 3Cl⁻

Aluminium trichloride reacts with hydrochloric acid and forms white fumes.

AlCl₃ + HCl → white fumes

Structure of Aluminium Hydroxide

Aluminium cation is attracted with three hydroxide anions.

Properties of Aluminium Hydroxide

The Colour of aluminium hydroxide is white.

Its density is 2.43 g/cm³.

Its melting point is 300 degrees celsius.

Its molar mass is 78.0036.

Aluminium Hydroxide Gel Preparation

Aluminium hydroxide is hydrophobic in nature. Generally, it forms lyophobic solutions. Aluminium hydroxide gel preparation can be done with the hydrolysis of aluminium chloride.

AlCl₃ + 3H₂O → Al(OH)₃ + 3HCl

Step by Step Aluminium Hydroxide Gel Preparation

1. Prepare the 2% aluminium chloride solution (by adding 2g of aluminium chloride in 100 ml water).

2. Add 100 ml distilled water to the conical flask.

3. Boil the water with the help of the wire gauze.

4. Add 10 ml of the above prepared 2% aluminium chloride solution. Add this solution with the help of the dropper of the burette. As aluminium compounds are violent in nature.

5. Constantly stir the solution while adding aluminium chloride.

6. Heat the solution until you see a coloured solution. The colour of the aluminium hydroxide solution is white.

7. Leave the mixture for cooling at normal temperature.

8. The cooling solution is called aluminium hydroxide gel.

9. Precaution You Need to keep During Aluminium Hydroxide Gel Preparation

10. Clean the conical flask with a steaming process to avoid any kind of impurities.

11. The byproduct (Hydrochloric Acid) formed in this reaction causes destabilization of the prepared gel. therefore, needs to be removed by the dialysis process.

12. Aluminium chloride solutions need to be added in a dropwise manner.

Uses of Aluminium Hydroxide Gel

• It is used for treating gastric ulcers.

• It is used in making vaccines.

• It is used in cosmetics.

• It serves as an intermediate compound in various reactions.

• It is used as a flame retardant.

• It is used in the manufacturing of certain drugs.

Side Effects of Aluminium Hydroxide Gel

Aluminium hydroxide is generally used as a medicine. But to some people, it shows side effects when consumed. These side effects involve:

• Constipation is a possibility. Other issues, such as haemorrhoids and intestinal blockage, could result as a result of this. Contact your doctor or pharmacist right away if constipation persists or worsens.

• If your doctor has prescribed this drug, ensure that he or she has determined that the benefits are more and the side effects are negligible. The majority of people who use this medication experience no significant side effects.

• Exercise daily and drink ample amounts of water to avoid constipation. Constipation can be avoided by taking this medicine with a magnesium-containing antacid. Stool softeners may be beneficial as well. Other antacids, stool softeners, and laxatives might be discussed with your doctor or pharmacist.

• In the intestines, aluminium-containing antacids bind to phosphate, a vital physiological component. If your kidneys are normal, this can result in low phosphate levels, especially if you take big dosages for a long time.

• Get medical help right away if you experience any of the following side effects or symptoms of a serious medical problem: black/ta
  rry stools, mental/mood disorders (e.g., confusion, deep sleep), pain with urination, stomach/abdominal pain, or vomit that looks like coffee grounds. 

• This medicine seldom causes a severe allergic reaction. However, if you witness any symptoms of some allergic response, such as a rash, redness, itching/swelling (particularly of the face/tongue/throat), extreme dizziness, or shortness of breath, go to the doctor right away.

• This is a very important list of some potential adverse effects. Contact your doctor or pharmacist if you have any other side effects not listed above.

Aluminium Hydroxide: How to Use It

Before each dose, give the bottle a good shake. The flavour of the suspension may be improved by refrigerating it. Do not allow yourself to become frozen. This drug is most effective when taken without any other liquids. If necessary, dilute your dose with a little water.

This contains aluminium, which can interfere with the absorption of other medications (such as digoxin, iron, tetracycline antibiotics, pazopanib, and quinolone antibiotics like ciprofloxacin). To avoid this problem, talk to your doctor or pharmacist about how to schedule your medications.

If your acid problems persist or worsen after one week of use, or if you suspect you have a significant medical concern, seek medical help right away. 

Did You Know?

• Aluminium hydroxide reacts with both acid and base.

• Aluminium hydroxide is used in coating TiO2 nanoparticles.

• Aluminium hydroxide is used to reduce phosphate levels in people with certain kidney conditions.

• Aluminium hydroxide consumption reduces the absorption of the other medicines in the body. Therefore, two-hour gaps before and after taking aluminium hydroxide should be maintained for consuming other medicines with this.

Hence the article is very useful for the students to understand the properties, structure of aluminium hydroxide. Step by Step procedure of preparation of aluminium hydroxide gel is given in the above article.

A chemical compound is a compound which is formed from the atoms of different elements combined in a specific ratio. The various types of atoms are joined by chemical bonds. Every compound has a fixed ratio between the elements. The elements combine together so strongly that the compound behaves like one substance. 

Chemical compounds can be in the form of liquid such as water, which is made from the atoms of hydrogen and oxygen sticking together. Chemical compounds can be in the form of solid such as sodium chloride which is made from the atoms of sodium and chlorine sticking together. Some chemical compounds are dangerous to use if they are not handled with proper safety measures. There are many chemical compounds, which we use in our daily life, and today we will talk about such a chemical Compound.

Overview of Ammonium Chloride

Ammonium chloride is an inorganic chemical compound. Ammonium Chloride is a white crystalline salt that is highly soluble in water. Ammonium Chloride is composed of ammonium and chloride ions. Ammonium Chloride is a colourless chemical compound. The nature of the solutions of ammonium chloride is mildly acidic. The other names of ammonium chloride are Sal ammoniac, Salmiac, Nushadir salt, Sal Armagnac, Salt Armoniack, Salmiak.

Sal ammoniac is a natural, mineralogical form of ammonium chloride. Sal ammoniac is generally formed on burning coal dumps from the condensation of coal-derived gases. Sal ammoniac is also found around some types of volcanic vents. Sal ammoniac is majorly used as fertiliser and a flavouring agent in some types of liquor. Sal ammoniac is the product from the reaction of hydrochloric acid and ammonia.

Structure of Ammonium Chloride

The Structure of NH4Cl or Ammonium Chloride is represented as follows.

Properties of Ammonium Chloride

Let us look at the properties of Ammonium Chloride

Production of Ammonium Chloride

Ammonium Chloride is the product of the Solvay process. Apart from the Ammonium chloride, the sodium carbonate is another product of the Solvay process.

[ CO_{2} + 2 NH_{3} + 2NaCl + H_{2}O rightarrow 2NH_{4}Cl + Na_{2}CO_{3} ]

Usually, this method is used to minimise the release of ammonia from some industrial work. Commercially, ammonium chloride is prepared from the combination of ammonia (NH₃) with either hydrogen chloride (gas) or hydrochloric acid.

[ NH_{3} + HCl rightarrow NH_{4}Cl ]

Reactions with Ammonium Chloride

To release ammonia gas, ammonium chloride reacts with the strong base.

[ NH_{4}Cl + NaOH rightarrow NH_{3} + NaCl + H_{2}O ]

Ammonium chloride reacts with the alkali metal carbonates at the increased temperature which gives the ammonia and alkali metal chloride.

[ 2NH_{4}Cl + Na_{2}CO_{3} rightarrow 2NaCl + CO_{2} + H_{2}O + 2NH_{3} ]

When heated, Ammonium chloride shows a neutral nature, but in reality, ammonium chloride decomposes into ammonia, and hydrogen chloride gas on the heat.

[ NH_{4}Cl rightarrow NH_{3} + HCl ]

The solution of ammonium chloride in water has a pH in the range of 4.6 to 6.0.

History of Ammonium Chloride

The ancient mention of the ammonium chloride was in 554 A.D. in China. There were two sources of ammonium chloride at the time. The first source was the vents of underground coal fires in Central Asia, specifically, in the Tian Shan Mountains. The second source of ammonium chloride was the fumaroles of the volcano Mount Taftan in southeastern Iran. The Ammonium chloride word is derived from the Iranian phrase anosh adur which means immortal fire. Ammonium chloride was transported at that time along the Silk Road eastwards to China and westwards to the Muslim lands and Europe. The Arabs of Egypt discovered ammonium chloride in 800 A.D. from the burning camel dung, and that source became an alternative source in Central Asia.

Application of Ammonium Chloride 

Fertilisers

The main application of ammonium chloride is as a source of nitrogen in fertilisers. In Asia, in the crops of rice and wheat, Ammonium chloride is used as a fertiliser.

Metalwork

In preparing metals which are to be tin coated, galvanised or soldered, Ammonium chloride is used as a flux. Ammonium chloride works as a flux which cleans the surface of workpieces. Ammonium chloride is used as a flux in solder as well.

Medicine

Ammonium chloride is used in the field of medicine too. Ammonium chloride is used in cough medicines. Ammonium salts are useful to reduce nausea and vomiting. In the treatment of severe metabolic alkalosis, Ammonium chloride is used as a systemic acidifying agent. Ammonium chloride is useful in the oral acid loading test to diagnose distal renal tubular acidosis too.

Food

Ammonium chloride is used as a yeast nutrient in breadmaking and as an acidifier. In dark sweets called Salmiak, Ammonium chloride is used to spice up. Salmiak is a dark sweet which is popular in Nordic and other nearby countries. In baked cookies, ammonium chloride is used to bring the crisp texture. Ammonium chloride is called the Noshader in Iran, Tajikistan, India, Pakistan, and some Arab countries. In samosas and jalebi, ammonium chloride is used to improve the crispness.

In the Laboratory

To produce low temperatures in cooling baths, Ammonium chloride is used. As a buffer solution, ammonium chloride is used with ammonia. In palaeontology, the vapour of ammonium chloride is cemented on fossils; this stuff forms a white layer which can be easily removed and it is quite harmless.

Flotation

With the help of ammonium
chloride solution, Giant squid and some other large species of squid maintain the neutral buoyancy in seawater because the density of the solution of Ammonium chloride is less than the density of seawater. The solution of ammonium chloride tastes like Salmiakki, and because of this unusual taste, giant squids feel un-attracted towards the human.

Other Applications

To reduce the clay swelling problems, ammonium chloride is used for 5% in aqueous solution. Ammonium chloride is used as an electrolyte in Zinc-Carbon batteries. Ammonium chloride is used in hair shampoo, and cleaning products too. Ammonium chloride is used as glue to attach two plywood. For dyeing, tanning, textile printing, and cotton clustering, ammonium chloride is used in textile and leather industries. In Leclanché cells, Ammonium Chloride was used in aqueous solution as an electrolyte in the start of the 20th century. Ammonium chloride is used in Iron which is used for clothes.

The anhydride is the chemical compound which is obtained, either in principle or in practice, by the elimination of water from any other compound. An example of inorganic anhydrides is given as sulfur trioxide, SO3, which has been derived from the sulfuric acid, and the calcium oxide, CaO, derived from calcium hydroxide. Sulfur trioxide including other oxides produced by the removal of water from acid is often known as acid anhydrides, whereas the ones such as calcium oxide, are produced by a base upon the loss of water are designated as basic anhydrides.

Importance of Anhydride

The most important compound of the organic anhydrides is acetic anhydride, with the chemical formula (CH3CO)2O. It can be prepared industrially in either two ways: and from acetic acid by the reaction with ketene or acetylene or by acetaldehyde‘s atmospheric oxidation in the presence of a metal acetate. Other organic anhydrides are prepared from the carboxylic acids by reaction with ketene, acetic anhydride, isopropenyl acetate or methoxy-acetylene. Also, anhydrides can be produced when acyl halides react with carboxylic acid and pyridine or acetic anhydride.

The organic anhydrides can be used to introduce the acyl group (RCO) in organic synthesis. They react with water to produce carboxylic acids, either with alcohols or phenols to form esters and with ammonia and amines to form amides. Acetic anhydride can be employed in cellulose acetate manufacturing, which is widely used as a base for the magnetic tape and in textile fibre manufacturing. Also, it can be heated with salicylic acid to form the medicinal chemical acetylsalicylic acid (which is called aspirin).

Preparation

Organic acid anhydrides can be prepared in the industry by various means. Mainly, acetic anhydride is produced by the carbonylation of methyl acetate. Maleic anhydride can be prepared by the oxidation of butane or benzene. Laboratory routes emphasize the corresponding acid’s dehydration. The conditions change from acid to acid, but the phosphorus pentoxide remains as a common dehydrating agent:

2 CH3COOH + P4O10 → CH3C(O)OC(O)CH3 + P4O9(OH)2

Mixed anhydrides, which contains the acetyl group can be prepared from ketene:

RCO2H + H2C=C=O → RCO2C(O)CH3

Acid chlorides are also effective precursors:

CH3C(O)Cl + HCO2Na → HCO2COCH3 + NaCl

Reactions

Acid anhydrides are the reactive acyl group source, and the reaction and use of acetic anhydride resemble those of acyl halides. With the protic substrate reactions, they afford similar amounts of the acylated product and the carboxylic acid:

RC(O)OC(O)R + HY → RC(O)Y + RCO2H

For HY = HOR (alcohols), aromatic ring (see Friedel-Crafts acylation), and HNR’2 (ammonia, primary, and secondary amines).

Acid anhydrides tend to be less electrophilic compared to acyl chlorides, and only one acyl group can be transferred per molecule of the acid anhydride, which can lead to a lower efficiency atom. However, the low cost of acetic anhydride makes it a common choice for the acetylation reactions.

Applications and Occurrence of Acid Anhydrides

Acetic anhydride is a primary industrial chemical, which can be widely used in the preparation of acetate esters. For example, cellulose acetate is the one. Maleic anhydride is also the precursor to multiple resins by copolymerization with styrene. And, maleic anhydride is a dienophile in the reaction of Diels-Alder.

Dianhydrides, the molecules containing two acid anhydride functions can be used to synthesize polyimides and at times, polyamides and polyesters. Examples of dianhydrides can be given as 3,3′, 4,4’-benzophenone tetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), 3,3′, 4,4′ – oxydiphthalic dianhydride (ODPA), benzoquinone tetracarboxylic dianhydride, ethylene tetracarboxylic dianhydride, and 4,4′-diphthalic (hexafluoroisopropylidene) anhydride (6FDA). Polyanhydrides are given as a class of polymers characterized by the anhydride bonds, which connect to the repeat units of the polymer backbone chain.

Natural products that contain acid anhydrides have been isolated from the bacteria, fungi, and animals. Some of the examples include cantharidin from the blister beetle species, including the Lytta vesicatoria, tautomycin, and Spanish fly, from the bacterium Streptomyces spiro verticillatus. The maleidride family of the fungal secondary metabolites that possess a wide range of antifungal and antibiotic activity are the alicyclic compounds with the functional groups of maleic anhydride.

Acid Anhydride

A molecule where two acid groups which contain more than one oxygen, bonded to each other, generally having displaced water in the process. (Thus the term “anhydride,” strongly implies an unspecified absence of the water at someplace). The resulting chemical structure can be represented as follows:

(Image to be added soon)

Where R and R₁ would be anything, and in some special cases, the carbon lying next to them can also be something. In other terms, the oxygens are representative and the bonds leading off them are the strict requirements, but everything else can be shown as something else.

In other special cases, the oxygen compounds are also swapped out for sulfurs, but this case is very rare, and the bond structure remains similar in this case.

Antioxidants are components that neutralize free radicals that play a vital role in cancer, heart disease, and various other diseases. Free radicals tend to be highly reactive chemicals and have the capability to destruct cells. They get formed when a molecule or an atom either loses or gains an electron. Free radicals are generated by the body as a response to radiation or environmental pressures. There are commonly two sources of antioxidants; artificial or natural. Some plant-based foods are commonly believed to be high in antioxidants, and plant-based antioxidants are believed to a type of phytonutrient. The human body, too, produces a few antioxidants, and they are recognized as endogenous antioxidants, whereas antioxidants that come from the outside of the human body are known as exogenous.

What are the Examples of Antioxidants?

Antioxidants, like carotenoids, Vitamin C, and Vitamin E, might help in shielding cells from the damage that free radicals cause, and some other naturally arising antioxidants comprise tannins, flavonoids, lignans, and phenols. Some plant-based foods are acknowledged as the finest sources, and they comprise vegetables, fruits, nuts, whole grains, cocoa, spices, herbs, and seeds. In the form of a bonus, vegetables, whole grains, and fruits that are rich in antioxidants are also commonly rich in fiber, excellent sources of minerals and vitamins, and low in cholesterol and saturated fat.

The Presence of Antioxidants in Foods

Every living thing needs antioxidants for its survival, and our body does generate its antioxidants, like cellular antioxidant glutathione. Again, some animals, plants, and various other kinds of lives too possess their defenses against oxidative damage as well as free radicals. So, it can be said that antioxidants are present in every whole food of animal and plant origin. Sufficient intake of antioxidants is vital, and our life is dependent on the consumption of some antioxidants, like Vitamin C and Vitamin E. Nonetheless, other non-important antioxidants too are present in our food. 

Though they happen to be unnecessary for our bodies, yet they do play a huge role in our general health. We get massive benefits from a diet that is rich in plants due to various antioxidants that they propose to us. Green tea, berries, dark chocolate, and coffee are quite popular for being excellent sources of antioxidants. Studies have proved that in the Western diet, coffee is the largest source of antioxidants, and it is partly as an average person does not eat many antioxidant-rich foods. Again, fish and meat products too contain antioxidants though not to the degree as vegetables and fruits. 

Antioxidants are hugely effective in increasing the shelf life of processed as well as natural foods, and so, they are habitually utilized in the form of food additives. For example, we often include Vitamin C to the processed foods for working as preservatives.

A Healthy Diet that Contains Antioxidants

When people eat a healthy diet, they get sufficient amounts of antioxidants, and it comprises a combination of vegetables and fruits. Seeds, nuts, and whole grains too propose good nutrients.

• Vitamin A – Vitamin A is present in eggs, liver, butter, and milk.

• Vitamin C – Vitamin C is found in many vegetables and fruits, and so, it is important to eat fruits, like oranges, berries, cantaloupes, papayas, and kiwis. Again, you must also eat vegetables, like broccoli, tomatoes, bell peppers, kale, Brussels sprouts, and cauliflower.

• Vitamin E – Vitamin E is present in some seeds and nuts, like sunflower seeds, almonds, peanuts, and hazelnuts. Some green leafy vegetables, like kale and spinach, are also good sources of vitamin E. Vitamin E is also present in sunflower, canola oils, corn, and soybean.

• Lycopene – It is found in both pink and red vegetables and fruits, and it comprises watermelon, tomatoes, apricots, and grapefruits.

• Beta-carotene – Beta-carotene is present in brightly-colored vegetables and fruits, and so, we need to eat fruits, like apricots, peaches, cantaloupes, mangoes, and papayas. It is also important to eat vegetables, like peas, squash, sweet potatoes, broccoli, and carrots. Beta-carotene is also present in many leafy green vegetables, like spinach, kale, and beet greens.

• Selenium – It is present in bread, pasta, and grains that comprise wheat, rice, and corn. Additionally, it is present in many animal products, such as turkey, chicken, fish, and beef. Selenium is also present in legumes, cheese, eggs, and nuts.

• Lutein – Lutein is present in some green leafy vegetables, like collards, kale, and spinach. Some other foods, like oranges, papayas, peas, corn, and broccoli too, are rich in Lutein.

The Tips to Increase Your Intake of Antioxidants

The following tips help increase your intake of antioxidants:

• You must eat a vegetable or fruit whenever you eat, and it includes snacks and meals.

• Drink a cup of matcha or green tea daily.

• Observe your plate’s color. When your food happens to be mostly beige or brown, then the levels of antioxidants happen to be low, and so, you need to include foods that have rich colors, like beets, berries, and kale.

• Use oregano, cumin, turmeric, clove, cinnamon, and ginger for spicing up the content of antioxidants and flavor of your meals.

• Make a habit to munch seeds and nuts, particularly Brazil nuts, dried fruits, and sunflower seeds. However, you must keep this in mind to select those that are devoid of salt or added sugar.

Some Delicious Recipes 

According to some registered dietitians, some delicious and healthy recipes are mentioned below:

• Carrot cake power smoothie

• Almond-cherry smoothie

• Cinnamon-ginger roasted carrots

• Cure-all juice

• Thai lettuce wraps

• Kale, cashew superfood soup, and chickpea.

• Red quinoa salad and roast beet along with the orange-beet balsamic vinaigrette

You need to keep this in mind that there isn’t any RDA or recommended daily allowance for antioxidants though you must intake various fresh plant-based products as they are viewed as healthy.

Advantages of Antioxidants

Dietary antioxidant vitamins comprise vitamin A, vitamin C, and vitamin E besides beta-carotene, lycopene, selenium, and lutein. Some diets that have plenty of antioxidants are connected with the following:

• Digestive function

• Immune function

• Eye health

• Skin health

• Brain function

• Blood sugar stability

• Cardiovascular health

• Prostate health

Different antioxidants do good to our body in various methods. For instance, beta-carotene has massive health benefits for eye health, and skin. Lycopene is good for prostate health and it helps in lessening the signs of BPH. Again, Vitamin C has various health benefits that include the protection of the heart and immune system. Hence, it can be said that antioxidants benefit your health and body in various ways and so you must discover methods for augmenting your consumption of antioxidants. The best method to accomplish this is by incorporating various highly antioxidant-rich foods into your diet.

Conclusion

People respond to antioxidants in several ways as they can result in negative effects or health risks on their health. For example, smokers run a huge chance of getting infected with lung cancer. Again, taking beta-carotene in huge doses can augment your chances of this disease. At times, antioxidants have an interaction with a few medicines also. When you eat healthily, you lessen your chances of getting infected with some diseases, but you need to keep this in mind that antioxidants alone can’t prevent chronic conditions. It is the wisest decision to consult your doctor before you take large dosages of antioxidants as your doctor would help you in determining the appropriate supplements that are ideal for your health and well-being.

Acids and bases are chemical compounds showing distinct properties which make them usable in certain scenarios. For instance, automobile batteries use sulphuric acid, few fertilisers and detergents use acids for its composition. Likewise, bases like Calcium Hydroxide find its application in the manufacturing of bleaching powder. These acids and bases have numerous applications in chemical units, industries, and day to day life. 

While these have numerous applications, exposure to strong acids and bases can be harmful to you. Therefore, it is important to adhere to the safety measures while handling these corrosive chemicals. 

Now, an acid or base can be defined in multiple ways as there are three proposed theories –

1. Arrhenius acid and base theory. 

2. Bronsted-Lowry definition. 

3. Lewis theory. 

Here, we will discuss Arrhenius theory of acids in details. 

Arrhenius Acid and Base Definition

A Swedish scientist Svante Arrhenius, in the year 1884, proposed acid and base as the two classifications of compounds. According to him, an acid is a compound which can readily give up protons or Hydrogen ion in aqueous or water solution. 

For instance, take this equation into consideration. 

HCl(aq) → H+(aq) + Cl–(aq) 

Here, the solution of Hydrochloric acid with water entirely dissociates them into Hydrogen and Chlorine ions. When this aqueous solution of HCl is mixed with water, it releases hydronium ions as shown by the equation below – 

HCl(aq) + H2O(l) → H3O+(aq) + Cl–(aq) 

In a similar manner, acids such as HBr, CH3COOH (acetic acid), HNO3 (Nitric acid), HI (Hydro-iodic acid), H2SO3 (sulphurous acid), H2SO4 (sulphuric acid), H3PO4 (Phosphoric acid), H2CO3 (Carbonic acid), HCIO4 (Perchloric acid), HF (Hydrofluoric acid) follow the Arrhenius concept. 

According to the theory, a compound is known as Arrhenius base if it dissociates into OH– ions in its aqueous or water solution form. 

For instance, consider this equation to understand this theory. 

NaOH (aq) → Na+ (aq) + OH– (aq) 

Here, the aqueous solution of NaOH produces Hydroxide ions exhibiting the property of base. 

Basicity Property of Arrhenius Acids 

The basicity of any acid is the measure of H+ ions it can release. Further, understand this concept with the help of the following reaction – 

H3PO4 → H+ + H2PO4–

H2PO4– → H+ + HPO42–

HPO42– → H+ + PO43–

From the above equations, it is clear that H3PO4 releases three Hydrogen ions in its aqueous or water solution. Therefore, the basicity of H3PO4 acid will be equal to 3. 

Further, look at the table drawn below that shows the basicity values of different acids. 

Arrhenius Acid as Electrolytes 

Arrhenius was trying to learn the reason behind the conduction of electricity in solutions. He found out that the reason for conductivity was ions, primarily. His observation led to the speculation that acids like HNO3, HCl, H2SO4, etc. behave as electrolytes when they are dissolved in water. 

As per the Arrhenius definition of acid, for an ideal strong electrolyte solution, if 100 molecules of HCl are mixed with water, then it releases 100 H+ & 100 Cl– ions. Ideally, there is no molecule of HCl in the solution as this acts as strong acid and reacts with water to produce ions. 

1. Strong Acid 

A strong acid has the capability to get completely dissociated or ionised in the aqueous solution so that it increases the number of protons or H+ ions in the solution. Here, the acid dissociation constant is represented as Ka and is proportional to the strength of an acid. Therefore, a strong acid has a high magnitude of Ka. 

2. Weak Acid 

Few compounds fail to dissociate completely when added to the aqueous solution. These are known as weak acids which are a solution of un-dissociated weak acid along with partially dissociated ions. In the solution, the number of H+ ions are extremely low and hence their pH value is greater than that of strong acids. For weak acids, magnitude of Ka or
the value of acid-dissociation constant is lesser than strong acids. 

Arrhenius Acid Example

The list of acids which qualify Arrhenius theory for acids is included in the table mentioned below. Have a look. 

In the solid or pure state, these exist as covalent compounds as the hydrogen ions are generated only when these are mixed with water as per Arrhenius acid base theory. 

Multiple-Choice Questions 

1. Choose the appropriate option which is true for Arrhenius acid. 

1. It is a compound which accepts hydrogen ions. 

2. When mixed with water, these release hydroxide ions. 

3. When mixed with water, these accept hydroxide ions. 

4. It is a compound which releases hydrogen ions in the solution. 

2. Choose the appropriate option which states the property of strong acid. 

1. The bond between hydrogen atoms and other elements is stronger in case of strong acids. 

2. Strong acids can easily bond with water. 

3. Strong acids are capable of dissociating entirely in the solution. 

4. Strong acids barely dissociate when mixed in the form of solution. 

3. If you pour an Arrhenius base into a beaker full of water, which ions will you find inside it? 

1. Hydroxide ions. 

2. Hydronium ions. 

3. Hydrogen ions. 

4. Water. 

4. Choose the appropriate option which depicts the hydronium ion formation. 

1. HCl (aq) —> H+ (aq) + Cl– (aq)

2. HCl(aq) + NaOH(aq) —> H20(l) + NaCl(aq)

3. H3O+(aq) —> H+(aq) + H20(l)

4. HCl(aq) —> H3O+(aq) + Cl–(aq)

5. Choose the appropriate option for application of pH scale. 

1. It is used to neutralise bases and acids. 

2. It is used for describing the chemical reaction between bases and acids. 

3. It is a scientific theory which helps determine the nature of bases and acids at a molecular level. 

4. It is utilised for measuring the concentration of hydrogen ions or hydronium ions in an aqueous solution.

Choose the right option for an aqueous solution whose pH range is in between 1 and 6. 

1. A base. 

2. An acid. 

3. A hydrocarbon. 

4. A neutral solution. 

7. Choose the appropriate equation depicting acid base neutralisation reaction. 

1. H3O+ (aq) —> H+(aq) + H20 (l)

2. HCl (aq) —> H+ (aq) + Cl

3. HCl (aq) + NaOH (aq) —> H20 (l) + NaCl (aq)

4. HCl (aq) —> H3O+ (aq) + Cl– (aq)

8. What is the effect of strong acid on litmus paper? 

1. It turns the red litmus paper blue. 

2. It turns the blue litmus paper blue. 

3. It turns the blue litmus paper blue. 

4. It turns the red litmus paper red. 

Now, get familiar with the important concepts related to Arrhenius with these study notes. You will be able to perform better in your examination and improve your knowledge about the two segregations of chemical compounds. So, if you want to give Arrhenius definition of an acid and a base precisely, refer to these study notes and learn with examples. You can also download ’s app for a more comprehensive learning approach. Refer to the study notes prepared by professional tutors and progress in your academic venture. 

An atom is smallest unit of matter which is made up of particles called protons, neutrons, and electrons. These smallest particles of atoms are responsible for the mass and charge of atoms. Atom is called the basic building block of chemistry. Most of the space of an atom used to be empty.  It is consists of a positively charged and small nucleus of protons and neutrons, these inner particles surrounded by electrons. Atom examples are Hydrogen (H), Iron (Fe), Copper (Cu) and Calcium (Ca) etc.  The atom diagram is given below.

Atomic Structure

Atoms are consists of 3 subatomic particles, protons, neutrons and electrons. The nucleus of an atom is formed by protons and neutrons and remain in the nucleus. Electrons orbit in a cloud form around the nucleus. In an atom, the number of protons used to be equal to the number of electrons and the number of protons is almost the same as neutrons but not always. An atomic number of an atom is defined as the number of protons present in the nucleus of an atom.  The atoms are electrically neutral hence the number of protons is equal to the number of electrons in an atom. Atomic weight indicates the relative weight with the atom of hydrogen (H) whose atomic weight is taken as unity.

Atomic Model

Many scientists have worked on the atomic structure from earlier times and they gave atomic structures and atomic models on the basis of their experimental observations. Some famous and important atomic models are as follows.

According to this model,

1.  Elements are made of small and indivisible particles called atoms.

2.  All atoms of the same element are identical and different elements have different types of atoms. 

3. Atoms can neither be created nor destroyed.

4. The formation of compounds took place when atoms of different elements join in simple proportions or ratios to form molecules.

Thomson model of an atom is also known as the watermelon model or plum pudding model of an atom. As per the model, the atom is made of electrons surrounded by a soup of positive charges to balance negative charges of the electrons in the same manner as “plums” (negatively charged)  surrounded by “pudding” (positively charged). In the mathematical model of Thomson, the corpuscles (which is now called electrons) were arranged in rotating rings non-randomly.

                      

The Rutherford model of the atom is considered the classic model of the atom In many ways, despite the fact that it is no longer considered an accurate representation. The atomic model of Rutherford represents that an atom is a mostly empty space where electrons orbits around a fixed and with electrons, positively charged nucleus in the set, predictable paths.

                    

Neils Bohr’s model of the atom was introduced in the year 1915 with the modification of Rutherford’s model of an atom. In his researches and experiments on atomic structure, he gave the following conclusions.

1. Electrons In an atom move around the nucleus which is charged positively in a definite circular path called orbits or shells.

2. These circular orbits are referred to as orbital shells and have fixed energy.

3. The energy levels are shown by an integer number (n=1, 2, 3…) which is called the quantum number. The quantum numbers start from the nucleus side with n=1 being the lowest energy level. The orbits n=1, 2, 3, 4… are termed as K, L, M, N…. shells and an electron is said to be in the ground state when an electron attains the lowest energy level.

4. The electrons in an atom move from a lower level of energy to a higher level of energy after attaining the required amount of energy and by loss of energy when an e- moves from a higher energy level to a lower level of energy.

• Quantum Mechanical Model of Atom

As per the Quantum mechanical model of the atom these points have been concluded. They are as follows.

1. The energy of an electron (e–) is quantized which means it can only have certain specific values of energy.

2. The electron’s quantized energy is the allowed solution of the Schrödinger wave equation and quantized energy is the result of wave properties of the electron.

3. According to the Uncertainty principle of Heisenberg, the exact position and momentum of an electron cannot be determined. So the only probability of finding an electron at a position can be determined and it is |ψ|² at that point where ψ represents the function of a wave of that electron.

4. The orbital of an atom is defined as the wave function of an electron. Every wave function or atomic orbital have some energy and shape associated with it. 

5. |ψ|² is probability density and have a positive value.
   

History and Facts of Atom

• The matter is made of building blocks that are not divisible. This idea was considered in early the 5th century BCE by Leucippus and Democritus. These particles were called “atomos” by the Greeks which means indivisible and in modern times the word “atom” is derived from this term.

• The concept that everything is made from atoms was firstly given by John Dalton in the year 1808.

• The atoms consist of two major parts. These are a nucleus of an atom and a cloud of electrons.

• The chemical behaviour of atoms is a result of the number of electrons and their arrangement in the electron cloud.

• The nuclear properties such as atomic mass, atomic number, nuclear cross-sections etc. of the element are determined by the number of protons and the number of neutrons.

• The number of atoms present in 1 mole (e.g. 12 grams of carbon) of a substance is equal to the constant of Avogadro that is equal to 6.022 x 10²³.

• The approximate size of atoms is 10⁻¹⁰ meters or 10⁻⁸ centimetres. The volume of an atom is around fifteen orders of magnitude larger than the volume of a nucleus.
  

Conclusion

Atomic structure is the basic chapter of chemistry which help to understand other complicated concepts of chemistry. We have learnt the basic properties of atom, atomic structures as well as different atomic models proposed by different scientists based on their observations and experiments.