Category: Class 11 Chemistry Objective Questions

Chemistry Multiple Choice Questions on “Homogeneous Equilibria”.

1. The equilibrium N_2(g) + O_2(g) (rightleftharpoons) 2NO_(g), is an example of _____________
a) homogeneous chemical equilibrium
b) heterogeneous chemical equilibrium
c) neither homogeneous nor heterogeneous
d) both homogeneous and heterogeneous
Answer: a
Clarification: In homogeneous equilibrium, the reactants and products are present in the same phase or physical state. Nitrogen, Oxygen, and nitrogen monoxide are present in a gaseous state, so it is homogeneous chemical equilibrium.

2. The units of K_P and K_C are equal.
a) true
b) false
Answer: b
Clarification: The units of K_P are (atm)^Δng and the units of K_C are (mol/L)^Δng. Where Δng = moles of products – moles of reactants which are in the gaseous state only. As the units of K_P and K_C are not equal the above statement is considered to be false.

3. Br₂(l) (rightleftharpoons) Br₂(g) is in ________
a) homogeneous equilibrium
b) not in both Homogeneous and heterogeneous equilibrium
c) cannot say
d) may or may not be in Homogeneous equilibrium
Answer: b
Clarification: As we know that in Homogeneous equilibrium the reactants and products are present in the same phase or physical state but here it is in a liquid state and gaseous state, so it is not in Homogeneous equilibrium.

4. Write pressure in terms of concentration and temperature.
a) P = CRT
b) P = nrt
c) p = CT
d) C = PT
Answer: a
Clarification: We all know that the ideal gas equation is PV = nRT; P = nRT/V; P = CRT here N/v is concentration, P is the pressure, V is the volume, n is the number of moles, C is the concentration, R is the universal gas constant and T is the temperature.

5. At constant temperature, the pressure is directly proportional to the concentration of the gas.
a) true
b) false
Answer: a
Clarification: We have P = CRT e where p is pressure, R is a universal constant and T is the temperature, we derive the equation from the ideal gas equation PV=nRT. So from P = CRT, we can say that at a constant temperature the pressure is directly proportional to the concentration of the gas.

6. For the following equation, 2HBr_(g) (rightleftharpoons) H_2(g) + Br_2(g); are both K_P and K_C are equal?
a) yes
b) cannot say
c) no
d) depends on the temperature
Answer: a
Clarification: We have here K_C = [H₂][Br₂]/[HBr]²; K_P = [pH₂][pBr₂]/[pHBr]², where pH₂ = [H₂]RT, pBr₂ = [Br₂]RT and [pHBr] = [HBr]RT. So in this case as Δng = 0, where Δng = moles of products – moles of reactants which are in gaseous state only, both K_P and K_C are equal.

7. What is the relation between K_P and K_C?
a) K_C = K_P
b) K_C = K_P(RT)
c) K_C = K_P(RT)^Δng
d) K_P = K_C(RT)^Δng
Answer: c
Clarification: For example, take the reaction 2HBr(g) (leftrightarrow) H_2(g) + Br_2(g), K_C = [H₂][Br₂]/[HBr]²; K_P = [pH₂][pBr₂]/[pHBr]², where pH₂ = [H₂]RT, pBr₂ = [Br₂]RT and [pHBr] = [HBr]RT. So we can say that K_C = K_P(RT)^Δng, where Δng = moles of products – moles of reactants which are in gaseous state only.

8. If K_C of a reaction N_2(g) + O_2(g) (rightleftharpoons) 2NO_(g) is 2 x 10^-3, then what is the K_P?
a) 4 x 10^-3
b) 1 x 10^-3
c) 3 x 10^-3
d) 2 x 10^-3
Answer: d
Clarification: As we know that K_C = K_P(RT)^Δng, here Δng = moles of products – moles of reactants which are in gaseous state only = 2 – (1+1) = 0. So K_C = K_P(RT)⁰, K_C = K_P(1) = K_P; K_C = K_P, therefore K_P is same as K_C and K_P is 2 x 10^-3.

9. CO_2(g) + C_(s) (rightleftharpoons) 2CO_(g) is an example of _____________
a) homogeneous equilibrium
b) heterogeneous equilibrium
c) neither homogeneous nor heterogeneous
d) both homogeneous and heterogeneous
Answer: b
Clarification: In heterogeneous equilibrium, the reactants and products are present in two or more physical States or phases. Here carbon dioxide is present in the gaseous state while carbon is present in the solid state, so it is an example of heterogeneous equilibrium.

10. WHat is the expression of K_C of the chemical equation Ag₂O_(s) + 2HNO_3(aq) (rightleftharpoons) 2AgNO_3(aq) +H₂O_(l)?
a) [AgNO_3(aq)]²/[HNO_3(aq)]²
b) [AgNO_3(aq)]/[HNO_3(aq)]²
c) [AgNO_3(aq)]²/[HNO_3(aq)]
d) [AgNO_(aq)]²/[HNO_3(aq)]²
Answer: a
Clarification: It is important that for the existence of heterogeneous equilibrium pure solid or liquid must also be at equilibrium, but their concentrations do not appear in the expression of the equilibrium constant. So here K_C = [AgNO_3(aq)]²/[HNO_3(aq)]².

Chemistry Multiple Choice Questions on “Hydrogen – Water”.

1. Water is amphoteric in nature.
a) true
b) false
Answer: a
Clarification: Yes, the above statement is true because water is amphoteric in nature. It acts as an acid when it is with a strong base and acts as a base when it is with strong acid. It is an oxidizing as well as a reducing agent.

2. Water reacts with ________________
a) metalloids
b) metals only
c) nonmetals only
d) both metals and nonmetals
Answer: d
Clarification: In redox reactions, water reacts with metals and nonmetals both. For example, take the reaction of sodium with water, the products are sodium hydroxide and hydrogen, whereas fluorine reacts with water in order to form hydrogen cation and fluorine anion with oxygen.

3. Water is of how many types in hydrated salt?
a) 1
b) 5
c) 4
d) 3
Answer: b
Clarification: In hydrated salt, there are five types of water. The five types of water in hydrated salt are i. coordinated water, ii. hydrogen bonded water, iii. lattice water, iv. clathrate water and v. zeolite water.

4. Compounds can undergo hydrolysis with water.
a) false
b) true
Answer: b
Clarification: Yes, a number of compounds such as calcium hydride(CaH), calcium phosphide(Ca₃PO₄), etc can undergo hydrolysis with water. Therefore we can say that compounds can undergo hydrolysis with water.

5. Do ice float on Water?
a) may be
b) yes
c) cannot say
d) no
Answer: b
Clarification: Ice floats on water, this is because of the density of ice i.e. mass per unit volume (density of ice is 0.9167 g/cm³ and density of water is 1g/cm³) is lesser than that of water. This is the reason, ice floats over water.

6. The type of hardness that occurs due to the presence of bicarbonate of calcium and magnesium ions hardness is _______________
a) half hardness
b) temporary hardness
c) permanent hardness
d) momentary hardness
Answer: b
Clarification: The water which forms come with soap is known as hard water. The hardness that occurs due to the presence of bicarbonates of calcium and magnesium is temporary hardness. Temporary hardness can be removed by boiling and Clark’s process.

7. What is the most efficient method to get water with zero degrees hardness?
a) Electrolysis
b) Permutit process
c) Synthetic resins
d) Calgon process
Answer: b
Clarification: Permutit is hydrated sodium aluminum silicate, it exchanges it’s sodium ions for divalent ions of calcium and magnesium, permutit when fully exhausted can be regenerated by treating with 10% of sodium chloride solution. It is the most efficient method to get water with zero degrees of hardness.

8. Which of the following is a method of removing temporary hardness?
a) boiling
b) adding washing soda
c) adding caustic soda
d) adding sodium phosphate
Answer: a
Clarification: The methods that are used for removing the temporary hardness of water are by boiling and by Clark’s process. Adding washing soda, caustic soda and sodium phosphates are for permanent hardness removal.

9. What is Calgon?
a) potassium Phantom metaphosphate
b) sodium penta metaphosphate
c) potassium hexametaphosphate
d) sodium hexametaphosphate
Answer: d
Clarification: Permanent hardness is removed by Calgon process. In this process, Calgon is referred to Sodium hexametaphosphate and its chemical formula is given by Na₆P₆O₁₈. This Calgon when added to hard water forms soluble complex.

10. Which of the following, do you think are the synthetic resins present in removal of permanent hardness?
a) cation exchange resins only
b) anion exchange resins only
c) both cation exchange resins and anion exchange resins
d) neither cation exchange resins nor anion exchange resins
Answer: c
Clarification: There are two types of synthetic resins used for removal of permanent hardness. They are cation exchange resins which are big molecules containing sulfonic acid group and an anion exchange resins which are also big molecules containing amino acids.

11. What is the hybridization of water?
a) spd
b) sp³
c) sp²
d) sp
Answer: b
Clarification: Water has a hybridization of sp³. In a water molecule oxygen has two lone pairs and two bonded hydrogens. Its structure is V in shape and has a bent structure. Water has a chemical formula of H₂O.

12. Pure water is a good conductor.
a) true
b) false
Answer: b
Clarification: As pure water is not a good conductor, we add a little amount of an acid or alkali or salt in order to make it a good conductor. The above-given statement that pure water is a good conductor, is considered to be false.

13. Water has a maximum density at _____ degree centigrade.
a) 32
b) 100
c) 0
d) 4
Answer: d
Clarification: Water has a maximum density at 4-degree centigrade, this is because at 4-degree centigrade, as opposite forces are in balance that is like the formation of Ice and maintaining of the liquid phase of water. Any less than 4-degree centigrade or greater than 4-degree centigrade, the water density is lesser than that of 4-degree centigrade.

14. Dielectric constant of water is ____________
a) 1
b) higher
c) 0
d) lower
Answer: b
Clarification: Water has a high dielectric constant and that is 78.39. The interaction of water with ionic substances is effective along with the release of energy in a noted quantity because of the Ion dipole interaction. This is applicable to the intercations with polar substances also.

15. Urea’s dissolution is because of __________
a) carbon bond
b) oxygen Bond
c) hydrogen bond
d) nitrogen bond
Answer: c
Clarification: The dissolution of covalent compounds like urea, glucose, and ethanol is due to the tendency of these molecules to form a hydrogen bond with water. Urea’s dissolution as because of the hydrogen bond.

Chemistry Multiple Choice Questions on “p-Block Elements – Important Compounds of Carbon and Silicon”.

1. Which of the following mixture is known as producer gas?
a) carbon dioxide and hydrogen
b) carbon monoxide and hydrogen
c) carbon monoxide and nitrogen
d) carbon dioxide and nitrogen
Answer: c
Clarification: The mixture of carbon monoxide and nitrogen is known as producer gas and the mixture of carbon monoxide and hydrogen known as water gas. At 1273 K carbon combines with oxygen and nitrogen in order to form producer gas.

2. Which of the following is not a property of carbon monoxide?
a) odourless
b) colourless
c) water-insoluble
d) oxidising agent
Answer: d
Clarification: Carbon monoxide is a colourless, odourless and almost water-insoluble gas. It is a powerful reducing agent. It is also used in the extraction of many metals from their oxide ores like ferrous oxide and zinc oxide.

3. Carbon dioxide forms carbonic acid with water.
a) true
b) false
Answer: a
Clarification: Carbon dioxide is given chemically by CO₂ and it is a colourless and odourless gas with water, it forms carbonic acid. The chemically balanced equation is given as H₂CO_3(aq) + H₂O → HCO₃^– + H₃O⁺.

4. What is the basic structural unit of a silicate?
a) Si₄^–
b) SiO^–
c) SiO₄
d) SiO₄^4-
Answer: d
Clarification: Silicates are the metal derivatives of silicic acid, H₂SiO₃ and can be obtained by fusing metal oxides or metal carbonates with sand. The basic structural unit of silicates is SiO₄^4-. An example is Zircon (ZrSiO₄).

5. What is the chemical formula of beryl?
a) Be₃Al₂Si₆O₁₈
b) Be₃AlSi₆O₁₈
c) Be₃Al₂Si₆O
d) BeAl₂Si₆O₁₈
Answer: a
Clarification: The chemical formula of beryl is given as Be₃Al₂Si₆O₁₈. Beryl is a type of cyclic silicate and it has two oxygen atoms shared and the basic unit is Si₆O₁₈^12-. It is known as beryllium aluminium cyclosilicate.

6. Talcum powder has a slippery touch.
a) True
b) False
Answer: a
Clarification: Talc consists of planar sheets which can slip over one another due to the weak forces of attraction and it is a constituent of talcum powder. That’s the reason why talcum powder has a slippery touch, So the above statement can be considered to be true.

7. What is the second hardest material known?
a) Coke
b) Carborundum
c) Graphite
d) Diamond
Answer: b
Clarification: Carborundum is the second hardest material known and has a formula of silicon carbide that is SiC. It is used as a semiconductor at high-temperature and also in transistor diode rectifiers. Diamond is the first hardest material known.

8. The cross-linked polymer compounds containing silicone which are linear and the cyclic are called ___________
a) coal
b) silicones
c) silicate
d) silicanes
Answer: b
Clarification: The linear, cyclic or cross-linked polymer compounds containing R₂SiO, as a repeating unit, is known as Silicones. They are manufactured from alkyl substituted chlorosilanes they are chemically inert, water repellent and also heat resistant.

9. Which of the following is not a component of glass?
a) Sodium chloride
b) Calcium carbonate
c) Silica
d) Sodium carbonate
Answer: a
Clarification: Glass is a transparent or translucent amorphous substance, which is obtained by fusion of sodium carbonate or sodium sulphate, calcium carbonate and sand (which is also known as silica), the general formula of glass is Na₂O.CaO.6SiO₂

10. When aluminium ions replace silicon ions and silicon dioxide what is it called?
a) silicanes
b) silicates
c) silicons
d) zeolites
Answer: d
Clarification: When aluminium ions replace few ions in a three-dimensional network of silicon dioxide, the overall structure is known as aluminosilicate and it also requires negative charge cations like sodium, potassium or calcium to balance negative charge. Few examples are zeolites and feldspar.

11. which of the following is not a part of the composition of natural gas?
a) hydrocarbons
b) methane
c) ethane
d) benzene
Answer: d
Clarification: Natural gas is found along with petroleum below the surface of the earth, its composition is methane, higher hydrocarbons, ethane and propane. It is used as a fuel and its combustion is carbon black which is a reinforcing agent for rubber.

12. What is the full form of LPG?
a) liquefied phenolic gas
b) liquefied pentane gas
c) liquefied petroleum gas
d) liquid petroleum gas
Answer: c
Clarification: The full form of LPG is liquefied petroleum gas and its composition is N-butane and isobutene. It is used as a domestic fuel. LPG, that is liquefied petroleum gas is commonly used in household for cooking.

Chemistry Multiple Choice Questions on “ Environmental Chemistry – Soil Pollution”.

1. Before World War II, which chemical was used for pest control?
a) DDT
b) Nicotine
c) Boric acid
d) Deltamethrin
Answer: b
Clarification: Prior to World War II, many naturally occurring chemicals such as nicotine were used as pest controlling substances for major crops in agricultural practices. This was achieved by planting tobacco plants in the crop fields.

2. Which one of the following chemicals has been banned in India?
a) Acephate
b) Deet
c) Metaldehyde
d) DDT
Answer: d
Clarification: During World War II, DDT was found to be of great use in the control of malaria and other insect-borne diseases. Therefore, after the war, DDT was put to use in agriculture to control the damages caused by insects, rodents, weeds, and various crop diseases. However, due to adverse effects, its use has been banned in India.

3. Pick out the correct characteristic of organic toxins.
a) insoluble, non-biodegradable
b) soluble, non-biodegradable
c) insoluble, biodegradable
d) soluble, biodegradable
Answer: a
Clarification: Organic toxins are poisonous substances derived from living organisms. Most of the organic toxins are water insoluble and non-biodegradable. These high persistent toxins are, therefore, transferred from lower trophic level to higher trophic level through food chain. Organic toxins are almost equally harmful as the synthetic chemicals to humans.

4. At each trophic level, the pollutant gets 10 times more concentrated.
a) True
b) False
Answer: a
Clarification: As we go up the food chain, the concentration of pollutant increases. This process is called biomagnification. This process refers to the buildup of toxins in the food chain. At each trophic level, the pollutant gets 10 times more concentrated. Therefore, the animals near the top of the food chain gets the most affected by the toxins.

5. Identify the substance that is not an organic toxin.
a) Aldrin
b) Dieldrin
c) Hydrogen sulphide
d) Toxaphene
Answer: c
Clarification: Hydrogen sulphide is not an organic toxin. It is an inorganic toxin. It exists in the gas phase at ambient temperatures, if finely divided or has a high vapor pressure. But, hydrogen sulphide, becomes far less toxic, when oxidized. Aldrin, Dieldrin, and Toxaphene are organic toxins.

6. Pick out the correct statement about carbamates from the following.
a) They are less harmful to human life
b) They offer excellent insect-resistance
c) They are less persistent
d) They are non-biodegradable
Answer: c
Clarification: Carbamates are less persistent and more biodegradable products. They were introduced in response to high persistence of chlorinated organic toxins. But these chemicals are severe nerve toxins and hence more harmful to humans. Insects have become resistant to these insecticides also.

7. Identify the correct statement regarding negative soil pollution.
a) Contamination of the soil due to addition of insecticides
b) Reduction in soil productivity due to soil erosion
c) Reduction in soil productivity due to the addition of pesticides and herbicides
d) Contamination of the soil due to natural disasters.
Answer: b
Clarification: Negative soil pollution is caused due to the overuse of soil and also due to soil erosion, and thereby, leading to decrease in soil productivity and efficiency. The other factors that can contribute to negative soil erosion are developmental activities, overgrazing, etc.

8. Pesticides and herbicides are the major components of chemical pollution.
a) True
b) False
Answer: b
Clarification: Pesticides and herbicides represent only a very small portion of the widespread chemical pollution. A large number of other compounds that are used regularly in chemical and industrial processes for manufacturing activities are finally released into the atmosphere in one or another form.

9. In the recent days, where has the pesticide industry has shifted to?
a) Stronger pesticides
b) Herbicides
c) Insecticides
d) Organo-chlorides
Answer: b
Clarification: These days, the pesticide industry has shifted its attention to herbicides. During the first half of the last century, this shift from mechanical to chemical weed control had provided the industry with flourishing economic market.

10. Which of the following is an herbicide?
a) Endrin
b) Lindane
c) Sodium chloride
d) Sodium arsinite
Answer: d
Clarification: Sodium arsinite is an herbicide. It is less persistent but toxic to mammals. It decomposes in a few months. Like organo-chemicals, this will also get concentrated in the food web. Some herbicides can also cause birth defects. Other examples of herbicides include diclofop, sodium chlorate, etc.

Chemistry Multiple Choice Questions on “Developments Leading to the Bohr’s Model of Atom”.

1. What’s the wavelength for the visible region in electromagnetic radiation?
a) 400 – 750 nm
b) 400 – 750 mm
c) 400 – 750 μm
d) 400 – 750 pm
Answer: a
Clarification: Electromagnetic spectrum is made up of various electromagnetic radiation. They are radio waves, X-rays, gamma rays, UV rays, the visible region, IR waves, and microwaves. Visible rays are the only ones which a human eye can see. They range from 450 – 750 nm.

2. What is the wavenumber of violet color?
a) 25 x 10³ mm^-1
b) 25 x 10³ m^-1
c) 25 x 10³ cm^-1
d) 25 x 10³ nm^-1
Answer: c
Clarification: The wavenumber is the reciprocal or the inverse of wavelength. Wavenumber = 1/Wavelength. Its unit is cm^-1. The wavelength of violet color is 400nm as seen in the electromagnetic spectrum. So wavenumber = 1/400nm = 25 x 10³ cm^-1.

3. Calculate the frequency of the wave whose wavelength is 10nm.
a) 2 Hz
b) 3 Hz
c) 1 Hz
d) 4 Hz
Answer: b
Clarification: The relation between wavelength(λ) and frequency(v) of a wave is given by λ = c/v where c is the speed of light of the light. v = c/λ Frequency of the given wave = (3 x 10⁸m/s)/(10 x 10^-9m) = 3 Hz.

4. If Energy = 4.5 KJ; calculate the wavelength.
a) 4.42 x 10^-29 m
b) 4.42 x 10^-39 m
c) 4.42 x 10^-25 m
d) 4.42 x 10^-22 m
Answer: a
Clarification: We know E = hv through Planck’s Quantum Theory, where E is energy, h is Planck’s constant and v is the frequency. 4.5 KJ = (6.626×10^–34 Js)(3 x 10⁸m/s)/(wavelength). wavelength = 4.42 x 10^-29 m.

5. ________ frequency, is the minimum frequency required to eject an electron when photons hit the metal surface.
a) Required
b) Activated
c) Threshold
d) Limiting
Answer: c
Clarification: In the photoelectric effect, when photons strike on a metal surface, it emits electrons. Thus for emitting an electron, it requires a minimum amount of energy. This is threshold energy acquired through threshold frequency.

6. A metal’s work function is 3.8KJ. Photons strike metal’s surface with an energy of 5.2 KJ. what’s the kinetic energy of the emitted electrons?
a) 3.8 KJ
b) 5.2 KJ
c) 9 KJ
d) 1.4 KJ
Answer: d
Clarification: As per the formula of the photoelectric effect, we have E = K.E. + W_o. E is the energy of photons; K.E. is the kinetic energy with which electrons are emitted and W_o is the work function. K.E. = 5.2 KJ – 3.8 KJ = 1.4 KJ.

7. When an electron jumps from 3^rd orbit to 2^nd orbit, which series of spectral lines are obtained?
a) Balmer
b) Lyman
c) Paschen
d) Brackett
Answer: a
Clarification: As per the spectral lines of the hydrogen, when an electron jumps from n_th orbit to 2^nd orbit, it’s in Balmer series (provided that n = 3, 4, 5….). For Balmer series, the electron emits waves in visible region.

8. Find out the wavenumber, when an electron jumps from 2^nd orbit to 1^st.
a) 82357.75 cm^-1
b) 105,677 cm^-1
c) 82257.75 cm^-1
d) 109,677 cm^-1
Answer: c
Clarification: The Swedish spectroscopist, Johannes Rydberg gave a formula; Wavenumber = R_H[(1/n₁)²-(1/n₂)²]. Here R_H is the Rydberg constant and is equal to 109,677 cm^-1. Wavenumber = 109,677(3/4) = 82257.75 cm^-1.

9. The ultraviolet spectral region is obtained in Balmer series.
a) True
b) False
Answer: b
Clarification: When an electron jumps from n^th orbit to 1st orbit, provided that n = 1, 2, 3, etc, it emits radion in the ultraviolet region. As per the spectral lines of the hydrogen, when an electron jumps from n^th orbit to 2^nd orbit, it’s in Balmer series (provided that n = 3, 4, 5….). For Balmer series, the electron emits waves in the visible region.

10. During the photoelectric effect, when photons strike with 5.1eV, electrons emitted from which metal have higher kinetic energy?

a) Na
b) Ag
c) Equal
d) Neither
Answer: a
Clarification: As per the formula of the photoelectric effect, we have E = K.E. + W_o. E is the energy of photons; K.E. is the kinetic energy with which electrons are emitted and W_o is the work function. K.E. of Na and Ag are 2.8 eV and 0.8 eV.