Category: Class 12 Chemistry Objective Questions

Chemistry Multiple Choice Questions on “Biomolecules Carbohydrates – 2”.

1. Which of the following monosaccharides is a ketohexose?
a) Glucose
b) Galactose
c) Fructose
d) Mannose
Answer: c
Clarification: Fructose is a monosaccharide that consists of six carbon atoms including a carbonyl carbon of a keto group within its chain. Glucose, galactose and mannose are examples of aldohexoses.

2. Identify the aldose form the following.
a) Arabinose
b) Xylulose
c) Ribulose
d) Sorbose
Answer: a
Clarification: Arabinose consists of an aldehydic group (CHO) at the end of its chain which has a total of five carbon atoms (including the CHO group), hence it is an aldopentose. Xylulose, ribulose and sorbose are examples of ketoses.

3. Erythrulose is a/an _______
a) aldotetrose
b) aldoheptose
c) ketotetrose
d) ketoheptose
Answer: c
Clarification: Erythrulose is a tetrose carbohydrate (because it contains 4 carbon atoms) with the formula C₄H₈O₄. It has one ketone group and hence belongs to the ketose family.

4. Identify from the following pairs, a pair of aldoses.
a) Sorbose, allose
b) Mannose, tagatose
c) Psicose, gulose
d) Talose, idose
Answer: d
Clarification: All the compounds mentioned are monosaccharides with the formula C₆H₁₂O₆. However, allose, mannose, gulose, talose and idose are aldohexoses. Sorbose, tagatose and Psicose are aldoketoses.

5. Glucose is prepared commercially from the hydrolysis of ______ by boiling it with dilute H₂SO₄ at 393K under pressure.
a) starch
b) sucrose
c) galactose
d) dextrose
Answer: a
Clarification: An aqueous solution of corn starch is acidified with dilute H₂SO₄. This is then heated under pressure (2-3 bar) for hydrolysis to take place. After this, the liquid is neutralised with sodium carbonate and the resulting solution is concentrated under reduced pressure to get glucose crystals. This process is also used for obtaining glucose from cellulose.

6. Identify ‘X’ in the following reaction.

a) sucrose
b) lactose
c) maltose
d) starch
Answer: a
Clarification: When sucrose (C₁₂H₂₂O₁₁) is boiled with dilute HCl or H₂SO₄ in an alcoholic solution, glucose and fructose are obtained in equal amounts. This is one the methods used for preparation of glucose.

7. The reaction of glucose with which of the following proves the presence of an aldehydic group?
a) Potassium iodide
b) Hydroxylamine
c) Bromine water
d) Acetic anhydride
Answer: c
Clarification: On treatment with Br₂ water, glucose gets oxidised to gluconic acid (which is a six-carbon carboxylic acid). This indicates that the carbonyl group is present as an aldehyde group.

8. Glucose on Fehling’s test gives ______
a) no reaction
b) silver mirror
c) red precipitate
d) pungent gas
Answer: c
Clarification: Since glucose is readily oxidised, it acts as a strong reducing agent and reduces Fehling’s reagent to form a carboxylate compound (in the place of CHO group which gets oxidised) along with a red precipitate of Cu₂O.

9. The reaction of glucose with hydrogen cyanide confirms the ______
a) straight chain structure of glucose
b) presence of a carbonyl group in glucose
c) presence of an aldehyde group in glucose
d) presence of a keto group in glucose
Answer: b
Clarification: Glucose reacts with hydrogen cyanide to form glucose cyanohydrin, where the carbonyl double bond gets cleaved to form one C-OH bond and one C-CN bond. This indicates the presence of a carbonyl group but does not confirm whether it is an aldehydic or a keto group.

10. The reaction of glucose with acetic anhydride conforms the presence of how many hydroxy groups in glucose?
a) 3
b) 4
c) 5
d) 6
Answer: c
Clarification: The reaction of glucose with (CH₃CO)₂O gives glucose pentaacetate, which has five acetyl groups in the structure. This reaction also proves that all the five OH groups are present at different carbon atoms, because of the stable nature of glucose.

11. Identify the product of the following reaction.

a) Gluconic acid
b) Glutaric acid
c) Glutamic acid
d) Glucaric acid
Answer: d
Clarification: Strong oxidising agents like nitric acid oxidise both the terminal groups of glucose to give a dicarboxylic acid, saccharic acid, also known as glucaric acid. This reaction also indicates the presence of a primary alcoholic group. Gluconic acid also undergoes a similar reaction.

12. Glyceraldehyde is a carbohydrate.
a) True
b) False
Answer: a
Clarification: Glyceraldehyde is the simplest of the common aldose monosaccharides. It is a triose monosaccharide with the formula C₃H₆O₃. It consists of two hydroxy groups and one aldehydic group.

13. Identify the compound from its structure as derived from that given by Fischer.

a) Glucose
b) Gluconic acid
c) Saccharic acid
d) Sorbitol
Answer: c
Clarification: Gluconic acid (as shown) is obtained when D-glucose is treated with bromine water, resulting in the oxidation of the aldehyde group to a carboxyl group. Gluconic acid on further oxidation gives saccharic acid.

14. The reaction of glucose with NH2OH gives _______
a) n-hexane
b) glucose oxime
c) glucose cyanohydrin
d) a gluconic acid
Answer: b
Clarification: Glucose reacts with hydroxylamine to form an oxime of glucose, where a carbon-nitrogen double bond is formed (C=N-OH) in place of the CHO group. This reaction establishes the presence of a carbonyl group in glucose.

15. The ‘D’ in D-(+)-glucose represents its dextrorotatory behaviour.
a) True
b) False
Answer: b
Clarification: The ‘D’ represents the correlation of the structure to that of (+)-glyceraldehyde, in which the OH attached to the carbon adjacent to the CH₂OH is on the right-hand side of the chain. Likewise, when the OH of the last asymmetric carbon in glucose lies on the left-hand side of the chain, it is known as L-glucose.

Chemistry Multiple Choice Questions on “Drug-Target Interaction”.

1. Drugs that block the binding site of an enzyme form a substrate are called ______
a) inhibitors
b) poisons
c) messengers
d) receptors
Answer: a
Clarification: Drugs that either prevent the enzyme from holding the substrate or prevent it from providing functional groups that attack the substrate, are called enzyme inhibitors. These inhibit the catalytic activity of enzymes.

2. Which of the following drugs will inhibit the activity of the shown enzyme?

a) A
b) B
c) C
d) D
Answer: a
Clarification: The shape of the active site resembles a triangle, which means that the substrate should also have a similar shape. The drug that will inhibit the activity of this enzyme should closely resemble the substrate and block the active site. These are called competitive inhibitors.

3. All drugs block enzyme activity by occupying the active site before the substrate.
a) True
b) False
Answer: b
Clarification: Drugs prevent the attachment of substrate to enzymes by two different ways. One is the competitive approach where it occupies the active site, and the other is non-competitive way in which it does not occupy the active site.

4. A certain compound X occupied a site of an enzyme exactly opposite to that of the active site. This immediately resulted in the change of shape of the active site. X is called a ______
a) competitive inhibitor
b) non-competitive inhibitor
c) competitive messenger
d) receptor
Answer: b
Clarification: Non-competitive inhibitors are drugs that affect the catalytic activity of enzymes by changing the shape of the active site by binding to the enzyme at some other site. This prevents the substrate from binding to the enzyme.

5. A certain compound occupied a site Y of an enzyme near to the active site. This immediately resulted in the change of shape of the active site. Y is called a/an ______
a) inactive site
b) binding site
c) non-competitive site
d) allosteric site
Answer: d
Clarification: When a drug binds to an enzyme from a site other than the active site, it is called an allosteric site. Binding to this site causes the change in shape of active site such that the substrate cannot recognise it.

6. If the bond between the enzyme and inhibiting drug is very strong, which of the following takes place?
a) The active site slowly regains its original shape
b) The enzyme develops a new active site
c) The enzyme is blocked temporarily
d) The body synthesizes a new enzyme
Answer: d
Clarification: When there is a strong covalent bond between the enzyme and the drug, the enzyme is blocked permanently. This results in the degradation of the entire drug-enzyme complex and the synthesis of a new enzyme.

7. Which of the following is incorrect regarding receptors?
a) They have constant shape
b) They are proteins
c) The shape of receptors binding site changes to fit the messenger
d) They are present in the cell membrane
Answer: a
Clarification: Receptors are proteins that are embedded in the cell membrane with the binding site protruding outwards. They change the shape of the binding site to accommodate the incoming messenger and facilitate communication.

8. Which of the following is not a reason for the selectivity of receptors towards messengers?
a) Shape of binding site
b) Structure
c) Amino acid composition
d) Location in the membrane
Answer: d
Clarification: There are lots of different types of receptors in the body at different locations. They interact with different kinds of chemical messengers. Their selectivity for one messenger over the other is because of the difference in their binding sites, structure and composition of amino acids.

9. The drugs that are used when there is a lack of natural chemical messenger is called ______
a) antagonists
b) agonists
c) analgesics
d) narcotics
Answer: b
Clarification: Agonists are drugs that replicate the behaviour and properties of the chemical messenger and activate the receptor. These are used when the actual messenger is not present in the body.

10. Antagonists do not allow the transfer of message through receptors.
a) True
b) False
Answer: a
Clarification: Antagonists bind to the receptor at the binding site and inhibit its natural communicative function. This prevents the message to be passed into the cell.

Chemistry Multiple Choice Questions on “Vapour Pressure of Liquid Solutions”.

1. What phenomenon occurs when a solution’s equilibrium vapor pressure equals the surrounding atmospheric pressure?
a) Boiling
b) Melting
c) Condensation
d) Sublimation
Answer: a
Clarification: Boiling, by definition, occurs when the vapor pressure of a liquid equals the surrounding atmospheric pressure. It is a very quick vaporization process which takes place at a constant temperature, referred to as the boiling point.

2. What is the boiling point of water?
a) 100 °F
b) 671.67 °R
c) 373 °C
d) 212 °r
Answer: b
Clarification: °R represents the temperature measured on Rankine scale. Typically, boiling point of water is measured as 100 °C on the Celsius scale. The conversion of Celsius to Rankine scale is R = C x 9/5 + 491.67.
Considering boiling point of water as 100 °C, R = 100 x 9/5 + 491.67 = 671.67 °R
°F, °r represent the Fahrenheit and Reaumur scale, respectively.

3. “Total pressure of gas mixture is the sum of individual pressures”. Which law is reflected in this statement?
a) Amagat’s law
b) Raoult’s law
c) Dalton’s law
d) Henry’s law
Answer: c
Clarification: Dalton’s of partial pressure states that for a non-reactive mixture of gases in a closed vessel, the total pressure of the mixture is the sum of pressures all individual gas components present. If gases A, B and C are present then, total pressure, P_total = P_A + P_B + P_C.

4. If a mixture of A and B boils at a temperature lower than the boiling point of either of the components, what kind of deviation does the mixture show?
a) No deviation
b) Maximum and minimum deviation from Raoult’s law
c) Negative deviation from Raoult’s law
d) Positive deviation from Raoult’s law
Answer: d
Clarification: Deviation is always exhibited by non-solutions. Non- ideal solutions do not obey Raoult’s behavior. This is because ΔH_mix, ΔV_mix ≠ 0. The cause for this is the intermolecular attractions. In this case, molecular attraction between A – B is weaker than that of A – A and B – B. Hence the easier it is to break the bonds and boil faster at a lower temperature than that of either of A and B.

5. What deviation is shown by a mixture of equimolar phenol and aniline?
a) Negative deviation
b) Positive deviation
c) No deviation
d) Alternating positive and negative
Answer: a
Clarification: Phenol and aniline both exhibit greater magnitude of hydrogen bonding due to the presence of hydroxyl and amine group, both possessing highly electronegative atoms of oxygen and nitrogen, respectively. The intermolecular hydrogen bonding is far greater than the degree of intramolecular hydrogen bonding which requires more thermal energy to break. Thus, there is an increase in the boiling point of the mixture.

6. If ethanol and chloroform are present in a molar ratio of 2:3 then what is the vapor pressure at 20° C if vapor pressures of pure liquids are 5.95 kPa and 21.17 kPa, respectively?
a) 16.692 kPa
b) 15.082 kPa
c) 8.731 kPa
d) 12.038 kPa
Answer: b
Clarification: Given,
P⁰_eth = 5.95 kPa
P⁰_chl = 21.17 kPa
Mole ratio of ethanol ∶ chloroform = 2 ∶ 3
Total number of parts = 2 + 3 = 5
Therefore, mole fraction of ethanol, X_eth = 2/5 = 0.4
Mole fraction of chloroform, X_chl = 3/5 = 0.6
From Raoult’s law, p_A = p⁰_A x X_A
P_eth = 5.95 x 0.4 = 2.38 kPa
P_chl = 21.17 x 0.6 = 12.702 kPa
From Dalton’s law, P_total = P_eth + P_chl
P_total = 2.38 + 12.702 = 15.082 kPa.

7. Considering a binary solution of components A and B obeys Raoult’s law, which of the following is true?
a) Total vapor pressure cannot be related to mole fraction of only one component
b) Total vapor pressure of one component varies non-linearly with another component
c) A plot of vapor pressures of both components gives a linear plot
d) Total vapor pressure of solution always decreases with increase in mole fraction of a component
Answer: c
Clarification: Raoult’s law states that the partial pressure of each component in the solution varies directly with its mole fraction in the solution. It is formulated as p_total = p_A + (p_B – p_A)x_B. From this, it is seen that when a graph is plotted, it gives a linear plot passing through origin. Total vapor pressure can be expressed as mole fraction of one component and that it varies linearly with the latter. However, total vapor solution may decrease or increase with increase in mole fraction of a component.

8. A volatile liquid with vapor pressure 85 kPa (at sea level, 25° C) is taken to the peak of Mt. Everest. Which of the following is true?
a) The vapor pressure of the solution decreases
b) The solution will condense quickly than when at sea level
c) The solution will vaporize quickly than when at sea level
d) The vapor pressure of the solution increases
Answer: d
Clarification: The vapor pressure of a liquid is independent of the pressure of surroundings. Any solution boils when its vapor pressure equals the surrounding atmospheric pressure. The atmospheric pressure decreases with increase in altitude. Due to this, the vapor pressure equals the atmospheric pressure in a shorter period of time when compared to at the solution being present at sea level. Therefore, the solution will vaporize quickly as the bowling point will reached faster.

9. Which of the following is caused by the addition of a non-volatile solute to a solvent?
a) Reduction in equilibrium of vapor pressure of solution
b) Increase in melting point of the solution
c) Decrease in the boiling point of the solution
d) Osmosis of solute in the solution
Answer: a
Clarification: This phenomenon is known as ‘relative lowering of vapor pressure’ which is a very common colligative property. When a non-volatile solute is added to a solvent, the upper surface of the solvent is covered partially. Hence, the solvent molecules do not bear maximum freedom to escape into the space as vapors. Consequently, there is a decrease in vapor pressure when compared towhat it would have been with pure solvent and no solute at all.

10. What does the vapor pressure of solvent containing a non-volatile solute, in a closed system directly vary with?
a) Mole fraction of solute
b) Mole fraction of solvent
c) Molarity of solute
d) Molarity of solvent
Answer: b
Clarification: More the solute, lower is the vapor pressure of the solvent when compared to that when it is in its purest form. In case of greater amount of non-volatile solute, more solvent can be added to raise the vapor pressure. Therefore, it is always directly proportional to the mole fraction of the solvent.

Chemistry Multiple Choice Questions on “Chemical Kinetics – Pseudo First Order Reaction”.

1. For a pseudo first-order reaction, what is the unit of the rate of the reaction?
a) s^-1
b) mol L^-1s^-1
c) mol^-1 L s^-1
d) mol^-2 L² s^-1
Answer: a
Clarification: The unit of the rate of the reaction (k) is (mol L^-1)^1-n s^-1, where n is the order of the reaction.
For a pseudo first-order reaction n=1.
So, (mol L^-1)^1-n s^-1 = (mol L^-1)^1-1 s^-1 = s^-1.

2. Reactions whose molecularity is one but order is more than one are known as pseudo first-order reactions.
a) True
b) False
Answer: b
Clarification: Pseudo first-order reactions are the reactions whose molecularity is more than one but follows first order kinetics. Acid hydrolysis of esters such as CH₃COOC₂H₅ in aqueous solution is an example for pseudo first order reaction.

3. Which of the following reactions is an example of a pseudo first-order reaction?
a) H₂ + Br₂ → 2HBr
b) CH₃CHO → CH₄ + CO
c) C₁₂H₂₂O₁₁ + H₂O → glucose + fructose
d) PCl₅ → PCl₃ + Cl₂
Answer: c
Clarification: The order of the reaction may be sometimes altered sometimes by changing the conditions, for example, taking one or more reactants in excess compared to the other. The molecularity of inversion of cane sugar is 2 but follows first order kinetics because water is present in excess.

4. Acid hydrolysis of esters such as CH₃COOC₂H₅ in aqueous solution is an example of a pseudo first-order reaction.
a) True
b) False
Answer: a
Clarification: The reaction involved in acid hydrolysis of CH₃COOC₂H₅ in aqueous solution = CH₃COOC₂H₅ + H₂O → CH₃COOH + C₂H₅OH. The rate law for the reaction is R=k[CH₃COOC₂H₅][H₂O], however, water is present in large excess and is assumed to be constant during the course of the reaction. So the rate law becomes R=k [CH₃COOC₂H₅] and follows first order kinetics.

5. The rate law for inversion of cane sugar is R=k [C₁₂H₂₂O₁₁][H₂O]. Find the concentration of sucrose if the rate of the reaction is 0.032 s^-1 and rate constant k=0.005.
a) 5.8 M
b) 6 M
c) 6.2 M
d) 6.4 M
Answer: d
Clarification: Given, rate constant k=0.005, rate of the reaction R=0.032 s^-1.
Inversion of cane sugar is a pseudo first order reaction and water is present in large excess so the rate law becomes R=k [C₁₂H₂₂O₁₁]
0.032= 0.005 [C₁₂H₂₂O₁₁]
[C₁₂H₂₂O₁₁]=6.4 M.

6. What is the rate law of hydrolysis of CH₃COOC₂H₅ in aqueous solution?
a) R=k [CH₃COOC₂H₅]²
b) R=k [CH₃COOC₂H₅]
c) R=k [CH₃COOC₂H₅] [H₂O]
d) R=kk’ [CH₃COOC₂H₅][H₂O]
Answer: b
Clarification: The reaction involved in acid hydrolysis of ester = CH₃COOC₂H₅ + H₂O → CH₃COOH + C₂H₅OH. So the rate law becomes R=k’ [CH₃COOC₂H₅][H₂O], since water is present in large excess it is assumed to be constant throughout the reaction.
R=k[CH₃COOC₂H₅], where k is k’ [H₂O].

7. Which of the following is not true for a pseudo first-order reaction?
a) The reaction follows first order kinetics
b) Molecularity of the reaction should be one
c) The reactants such as water are present in excess and are assumed to be constant throughout the reaction
d) Unit of the rate constant is s^-1
Answer: b
Clarification: The order of the reaction can be sometimes altered by taking one of the reactant in excess compared to the other. Pseudo first order reactions are those reactions in which the molecularity is more than one but follows first order kinetics.

8. Which of the following is not similar between a first order and pseudo first order reaction?
a) The molecularity is one in both the reactions
b) Both follows first order kinetics
c) The unit of rate constant is s^-1
d) The rate of the reaction depends only on one reactant

Answer: a
Clarification: Both first order and pseudo first order reactions follow first order kinetics as in the rate of the reaction depends only on one reactant and the unit for rate constant is s^-1 but the molecularity in first order reaction should be one where as in pseudo first order reaction the molecularity can be more than one. For example: Inversion of cane sugar.

9. Which of the following is not an example of a pseudo first-order reaction?
a) CH₃COOC₂H₅ + NaOH → CH₃COOH + H₂O
b) CH₃COOC₂H₅ + H₂O → CH₃COOH + C₂H₅OH
c) C₂H₅COOC₂H₅ + H₂O → C₂H₅COOH + C₂H₅OH
d) C₁₂H₂₂O₁₁ + H₂O → glucose + fructose
Answer: a
Clarification: The reactions CH₃COOC₂H₅ + H₂O → CH₃COOH + C₂H₅OH, C₂H₅COOC₂H₅ + H₂O → C₂H₅COOH + C₂H₅OH and C₁₂H₂₂O₁₁ + H₂O → glucose + fructose are examples of pseudo first order reaction because water is present in excess and is assumed to remain constant is all the reactions but the reaction CH₃COOC₂H₅ + NaOH → CH₃COOH + H₂O is an example of second order reaction and follows second order kinetics with rate law R=k [CH₃COOC₂H₅] [NaOH].

10. For the reaction C₂H₅COOC₂H₅ + H₂O → C₂H₅COOH + C₂H₅OH, find the concentration of [C₂H₅COOC₂H₅] if the rate constant k=0.2 and the rate of the reaction is 0.39 s^-1.
a) 2.87 M
b) 2.01 M
c) 1.99 M
d) 1.95 M
Answer: d
Clarification: The reaction C₂H₅COOC₂H₅ + H₂O → C₂H₅COOH + C₂H₅OH is a pseudo first order reaction and follows first order kinetics with rate law R=k[C₂H₅COOC₂H₅].
Given, rate of the reaction R=0.39 s^-1 and rate constant k=0.2
So, 0.39 = 0.2 × [C₂H₅COOC₂H₅]
[C₂H₅COOC₂H₅]=1.95 M.

Chemistry Multiple Choice Questions on “Uses of Aluminium, Copper, Zinc and Iron”.

1. Which metal is used for galvanising iron?
a) Brass
b) Zinc
c) Copper
d) Aluminium
Answer: b
Clarification: Zinc is used for galvanising iron to protect it from corrosion. Galvanisation is a process of applying a protective zinc coating on iron or steel to prevent it from rusting. The most common method in galvanising is hot-dip method.

2. Zinc dust is used as a reducing agent in the manufacture of paints.
a) True
b) False
Answer: a
Clarification: Yes, zinc dust is a strong reducing agent used in the laboratory. It is also used in the manufacturing of drugs. It is used as a precipitant for many metals like copper, iron, aluminium to purify the solution containing metals.

3. Which of the following metals is a good conductor of electricity and conducts electricity twice as much as the other elements?
a) Fe
b) Cu
c) Hg
d) Al
Answer: d
Clarification: Aluminium is light, cheapmetal and good conductor electricity and resists corrosion. It conducts electricity twice as that of copper. It is used for making transmission cables and for winding the moving coil of dynamos or motor.

4. In thermite process, what is the reducing agent used?
a) C
b) Zn
c) Na
d) Al
Answer: d
Clarification: Thermite process proceeds via a thermite reaction. Thermite reaction involves the oxidation of the metal aluminium by the oxide of another metal, usually iron oxide. In this reaction, since aluminium is the element being oxidised, it acts as a reducing agent.

5. What type of extraction is the carbon monoxide reduction process used for?
a) Cu
b) Ag
c) Fe
d) Sn
Answer: c
Clarification: The reduction of the ore. At the high temperature at the bottom of the furnace, carbon dioxide reacts with carbon to produce carbon monoxide. It is the carbon monoxide which is the main reducing agent in the furnace. In the hotter parts of the furnace, the carbon itself also acts as a reducing agent.

6. Which of the following is present in aluminium bronze alloy?
a) Bronze
b) Copper
c) Brass
d) Iron
Answer: b
Clarification: Aluminium bronze is an alloy made up of aluminium and copper. Its percentage composition is 95% of aluminium and 5% of copper. It is mainly used for making coins. It is a light strong alloy with golden lustre and resistant to corrosion.

7. In invar, what is the composition of iron and nickel?
a) Fe-64%, Ni-36%
b) Ni-68%, Fe-32%
c) Fe-36%, Ni-64%
d) Fe-62%, Ne-38%
Answer: a
Clarification: Invar (FeNe36) is an alloy of steel which is a combination of iron and nickel. It’s percentage of the composition is 64% of Iron and 36% of Nickel. It’s mainly used for making watches. It has practically no coefficient of expansion.

8. What is the name of the alloy of copper called which contains a composition of 30-35% of zinc?
a) Bronze
b) Duralumin
c) Magnalium
d) Brass
Answer: d
Clarification: Brass is an alloy of copper which contains 60% of copper and 40% of zinc. It is highly ductile in nature, corrosion resistant and is mainly used for making parts of machinery and condenser tubes. It is also used for making utensils.

9. Cast iron is the most important form of iron.
a) True
b) False

Answer: a
Clarification: Cast iron is the most important form of iron because of it’s resistance to abrasion and indentation, the ability to absorb energy and the ability to deform without fracture and the ability to return to original dimension after being deformed.

10. Which metal is used for making water and steam pipes?
a) Zinc
b) Aluminium
c) Copper
d) Iron
Answer: c
Clarification: Copper is used because of its high thermal conductivity. This is higher than all other metals except silver, a precious metal. Copper has a 60% better thermal conductivity rating than aluminium and a 3,000% better rating than stainless steel.

his set of Chemistry Multiple Choice Questions on “P-Block Elements – Oxoacids of Sulphur”.

1. What class of compounds do the oxygen based compounds of sulfur represent?
a) Acids
b) Bases
c) Neutral oxides
d) Amphoteric
Answer: a
Clarification: The oxygen compounds of sulfur represent the class of ‘oxoacids’ of sulfur. Generally, a non-metallic oxide is usually acidic in nature (given that exceptions like CO, N₂O, NO). Examples include sulfurous acid (H₂SO₃), sulfuric acid (H₂SO₄) and many more.

2. Which of the following is the most popular oxoacid of sulfur?
a) Sulfurous acid
b) Sulfuric acid
c) Peroxodisulfuric acid
d) Pyrosulfuric acid
View Answer

Answer: b
Clarification: Sulfuric acid is commonly used in industrial chemical manufacturing as a reactant or a laboratory reagent. The formula is H₂SO₄. It is one of the most powerful oxidizing and dehydrating agents in the chemical field and finds a number of application, such as production of fertilizers and dyes and many more.

3. Which of the following is produced third in the contact process?
a) Sulfur dioxide
b) Sulfur trioxide
c) Pyrosulfuric acid
d) Sulfuric acid

Answer: c
Clarification: In the first step, sulfur is converted to sulfur dioxide. Second step involves reacting it with more oxygen to form sulfur trioxide. Instead of reacting sulfur trioxide with water to form sulfuric acid directly, an alternative, safer method is utilized to dissolve sulfur trioxide gas in sulfuric acid to form oleum, also known as pyrosulfuric acid.

4. Why is sulfur trioxide not dissolved in water and but treated with existing sulfuric acid?
a) It is not economically feasible
b) Manufacturing plants cannot withstand the great pressure of dissolving sulfur trioxide in water
c) Sulfur trioxide just hydrates on dissolving with no chemical bonds form
d) The heat of dissolution is very high and potentially dangerous
Answer: d
Clarification: The reaction between sulfur trioxide and water is highly exothermic and releases great amount of energy that no plant, currently, has the ability to withstand. Due to potential risks of explosion and fire hazard, sulfur trioxide is not dissolved in water but treated with sulfuric acid to produce oleum. This can be diluted to desired concentrations.

5. What is the primary product when carbon is treated with concentrated sulfuric acid?
a) Carbon dioxide
b) Carbon monoxide
c) Carbon sulfate
d) Carbon sulfide
Answer: a
Clarification: Since sulfuric acid is a very strong oxidant, it oxidizes carbon to carbon dioxide. With excess of oxygen available from sulfuric acid and water, carbon monoxide is rarely formed. Carbon sulfate does not exist and carbon sulfide formed as a reaction between carbon and sulfur.

6. What is the acidity of peroxodisulfuric acid?
a) 1
b) 3
c) 4
d) Does not exist
Answer: d
Clarification: Acids do not bear acidity. The number of hydrogen ions released by an acid is referred to as its basicity. The formula of peroxodisulfuric acid is H₂S₂O₈ and can release 2 H⁺ ions, hence the acidity is 2.

7. What is the basicity of oleum?
a) 1
b) 7
c) 2
d) 3
Answer: c
Clarification: Basicity of acids refer to the number of H⁺ ions that can be released upon dissolution. In the case of oleum, which is also known as pyro sulfuric acid, the chemical formula being H₂S₂O₇, the basicity is 2.

8. In the contact process, SO₂ is passed twice through the catalytic converted. Why?
a) To produce less while converting to SO₃
b) Since the energy and power consumed is less
c) To increase the yield
d) To avoid choking hazards
Answer: c
Clarification: Sulfur dioxide is passed twice to increase the yield and conversion to form more sulfur trioxide. In the first pass, only 63-65% of sulfur dioxide is converted to sulfur trioxide. When passed for the second time, the conversion increases to 80% hence increasing the yield of sulfur trioxide. This can be repeated to achieve a maximum 99% conversion.

9. Which of the following conditions is the most suitable for manufacture of sulfuric acid in contact process?
a) High temperature and high pressure
b) Low temperature and high pressure
c) High pressure and low temperature
d) Low pressure and low temperature
Answer: b
Clarification: Since the forward reaction is exothermic, lower temperatures will favor higher yield. This is in accordance with the Le Chatelier’s principle that an equilibrium tends to attain its original form when external conditions are changed. Since the reactant is in gas phase, increasing pressure increases yield.

10. In the 17^th century, Johann Glauber first prepared sulfuric acid by burning sulfur with potassium nitrate with steam. A famous salt was then called to be Glauber’s salt. Which of the following is it?
a) Potassium nitrate
b) Potassium sulfate
c) Sodium sulfate
d) Potassium hydroxide
Answer: c
Clarification: Glauber salt is the famous name for the deca-hydrate sulfate salt of sodium. Its chemical formula is Na₂SO₄.10H₂O. It is also known as mirabilite. It is widely used as laxatives in several medications and helps removing excess doses of drugs from human body, such as paracetamol.

11. Which oxoacid of sulfur is commonly used for disinfecting swimming pools as well as delignification of wood?
a) Sulfuric acid
b) Peroxydisulfuric acid
c) Sulfoxylic acid
d) Peroxymonosulfuric acid
Answer: d
Clarification: The chemical formula of peroxymonosulfuric acid is H₂SO₅. Popularly known as Caro’s acid, it is widely known for its disinfecting properties. Due to its strong oxidizing property, it is used as the last option to remove any traces of organic compounds present as impurities.

12. Which of the following is also referred to as ‘Marshall’s acid’?
a) HO₃SOOSO₃H
b) HO₃SOSO₃H
c) HO₃SSO₃H
d) HO₃SSO₂H
Answer: a
Clarification: Marshall’s acid is the common name for peroxydisulfuric acid. It is prepared by the reaction between chlorosulfuric acid and hydrogen peroxide. Another method includes the electrolysis of concentrated sulfuric acid (60% – 70%) with platinum electrodes at high current density and voltage.

13. What is the pH of 1mM concentrated sulfuric acid?
a) 3.01
b) 2.75
c) 1.03
d) 2.00
Answer: b
Clarification: pH refers to the power of hydrogen ions in the acid solution. It is calculated as the negative logarithm of the concentration of hydrogen ions. In case of 1mM of conc. sulfuric acid it is found that the concentration of hydronium ions is 10^-2.75mol dm^-3.

14. Which of the following oxoacid sulfur is known not to bear any acid salt?
a) Sulfuric acid
b) Thiosulfuric acid
c) Sulfonic acid
d) Dithionic acid
Answer: d
Clarification: Dithionic acid is formulated as H₂S₂O₆ and is known to possess no acid salts i.e. salt formed due to the loss of one hydrogen ion. The diprotic salts of dithionic acid is known as dithionates which are mild oxidizing and reducing agents as well.