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Q1. Role of NH₄Cl in qualitative analysis of third group cations is

• to suppress the degree of dissociation of NH₄OH
• to increase the degree of dissociation of NH₄OH
• to provide acidic medium
• to provide basic medium

Solution

NH₄Cl provides NH₄⁺ ions which suppress the degree of dissociation of NH₄OH.

Q2. Which of the following statements can be made about the equilibrium constant (K)?

• It always remains the same at different reaction conditions.
• It increases if the concentration of one of the products is increased.
• It changes with changes in the temperature.
• It may be changed by the addition of a catalyst.

Solution

Equilibrium constant changes with changes in the temperature.

Q3. If the value of the solubility product for AgBr is 4.0 x 10^-12 at 25 °C, calculate the solubility of AgBr(s) in water.

• 5.0 x 10^-7
• 2 x 10^-6
• 2.5 x 10^-13
• 2.5 x 10^-6

Solution

For AB type salt , Solubility = K_sp^1/2

Q4. What is the molar solubility (s) of Ba₃(PO₄)₂ in terms of K_sp?

• s = K_sp^1/2      
• s = K_sp^1/5     
• s = [K_sp/27]^1/5    
• s = [K_sp/108]^1/5     

Solution

Ba₃(PO₄)₂ = 3Ba₂⁺ + 2PO₄^2- or, K_sp = (3S)³ . (2S)²    

Q5. Which of the following is not a case of physical equilibrium?

• NH_3(aq) → NH₄OH
• H₂O_(s)  → H₂O_(g)
• H₂O_(s)  → H₂O_(l)
• CO_{2 (g)} → CO_2(aq)

Solution

Formation of NH₄OH is a chemical process.

Q6. Which of the following correctly represents conjugate acid-base pair?

• BF₃, NH₃
• HCl, NaOH
• NH₃, H₂O
• HCl, Cl^-

Solution

HCl generates Cl^- after losing a proton thus is conjugate base of HCl.

Q7. Which one of the following is correct about a reversible chemical reaction at equilibrium?

• all chemical reactions have ceased
• the rates of the forward and reverse reactions are equal
• the rate constants of the forward and reverse reactions are equal
• the value of the equilibrium constant is 1

Solution

At equilibrium Point the rates of the forward and reverse reactions are equal.

Q8. Which of the following weak acids ionizes to give the strongest conjugate base?

• HClO
• CH₃COOH
• HF
• HNO₂

Solution

HClO is the weakest; a weak acid shall produce a strong conjugate base.

Q9. A mixture of  NH₄Cl and NH₄OH shows no change in pH upon addition small amount of HCl. This is because it is

• A neutral solution
• An acidic solution due to presence of NH₄Cl
• A buffer
• A basic solution due to presence of NH₄OH

Solution

A mixture of weak base and its salt with a strong acid serves as an basic buffer which resists changes in pH upon addition of small amount of acid or base.

Q10. A moles of A reactants react with b moles of B reactants to form c moles of product C. Which of the following is true for rate of reaction

• Rate = k[A][B]
• Rate = k [A]^a +  [B]^b
• Rate = k[A]^a[B]^b
• Rate = k[A]^a[B]^b/[C]^c

Solution

According to law of mass action Rate = k[A]^a[B]^b

Q11. Solubility of BaCl₂ if K_sp is 10^-6 at 25 °C is

• 10^-3 M
• 6.3 × 10^-3 M
• 10^-6 M
• Cannot be predicted

Solution

K_sp = [Ba²⁺ ][Cl^-]² 1 × 10^-6 = (s) (2s)² 1 × 10^-6 = 4s³ s = 6.3 × 10^-3 M

Q12. The solubility product expression for tin(II) hydroxide, Sn(OH)₂, is

• [Sn²⁺][OH^-]
• [Sn²⁺]²[OH^-]
• [Sn²⁺][OH^-]²
• [Sn²⁺]³[OH^-]

Solution

Sn(OH)₂  Sn²⁺ + 2OH^-      or         K_sp = [Sn²⁺][OH^-]²

Q13. Which of the following is not a case of chemical equilibrium?

• CaCO_3(s) → CaO_(s)  + CO₂
• NH₄Cl_(s) → NH₄Cl_(aq)
• N₂O_4(g)  → 2NO_2(g)
• 2 SO_{2 (g)} + O_{2 (g)} → 2 SO_3(g)

Solution

NH₄Cl_(aq) is aqueous solution of NH₄Cl_(s).

Q14. We eat a variety of foods still pH of our blood does not change every time. The reason is

• Stomach wall is resistant
• There are buffers in the blood which resist pH change
• Strong bases in the blood donot let pH change
• Strong acids in the blood donot let pH change

Solution

There are buffers in the blood e.g HCO₃^- and CO₃^2- buffer which resist pH change.

Q15. What is the K_sp expression for lead (II) chloride?

• [Pb²⁺][Cl^-]²
• [Pb⁺][Cl^-]²/[PbCl₂]
• [Pb²⁺]²[Cl^-]
• [Pb₂²⁺][Cl^-]²

Solution

PbCl₂    Pb²⁺ + 2Cl^- or, K_sp = [Pb²⁺][Cl^-]²     

Q16. The pOH of a solution of NaOH is 11.00. What is the [H⁺] for this solution?

• 1.0 x 10^-3
• 2.5 x 10^-3
• 5.0 x 10^-12
• 4.0 x 10^-12

Solution

  pOH = 14 - pH 11 = 14 - pH pH = 14 - 11 = 3 pH = - log [H⁺] -3 = log [H⁺] [H⁺] =Anti [- 3] [H⁺] = 0.001  

Q17. Common ion effect leads to suppression of degree of dissociation of

• Strong electrolyte
• Weak electrolyte
• Any electrolyte
• Acid or base available in solution

Solution

Common ion effect leads to suppression of degree of dissociation of weak electrolyte in the presence of  a strong electrolyte containing a common ion.

Q18. Which one of the following is the approximate pH of 0.01 M solution of NaOH at 298 k?

• 12
• 2.5
• 2
• 10^-2

Solution

Q19. When ice is in equilibrium with water then during equilibrium

• amount of ice is equal to amount of water.
• there is no melting and no freezing.
• amount of ice melting is equal to amount of water freezing.
• amount of ice melting is more than amount of freezing.

Solution

During equilibrium the amout of ice melting is equal to amount of water freezing.

Q20. In a chemical equilibrium K_c = K_p when:

• The number of moles of reactant entering into the reaction is more than the number of moles of product formed.
• The number of moles of reactant entering into the reaction is equal to the number of moles of product formed.
• The number of moles of reactant entering into the reaction is less than the number of moles of product formed.
• The reaction is not reversible.

Solution

, where Ã"ˆ†n = ( number of moles of gaseous product ) -  ( number of moles of gaseous reactant ).

Q21. Which one of the following will change the value of the equilibrium constant?

• changing temperature
• varying the initial concentrations of reactants
• varying the initial concentrations of products
• changing the volume of the reaction vessel

Solution

K have different values at different temperature it generally doubles at every 10 ^°C rise.

Q22. Solubility product is defined as

• product of molar concentration of ions of a salt as per stoichiometry in a saturated solution
• product of molar concentration of ions of a salt as per stoichiometry in a supersaturated solution
• product of molar concentration of ions of a salt as per stoichiometry in an unsaturated solution
• product of molar concentration of ions of a salt as per stoichiometry in a saturated solution at STP

Solution

Solubility product is product of molar concentration of ions of a salt as per stoichiometry in a saturated solution.

Q23. Which one of the following is a strong electrolyte?

• KCl
• HF
• HNO₂
• (CH₃)₃N

Solution

Being a salt of strong acid HCl and strong base KOH.

Q24. The relationship between the molar solubility in water, s, and K_sp for the ionic solid Fe(OH)₂ is

• K_sp = s³
• K_sp = 4s³
• K_sp = 2s²
• K_sp = s

Solution

For AB₂ type salt , K_sp = 4s³ where s is solubility in m/l

Q25. Consider the following solubility data for various chromates at 25 °C. Salt     K_sp Ag₂CrO₄ 9.0 x 10^-12 BaCrO₄ 2.0 x 10 ¹⁰ PbCrO₄ 1.8 x 10¹⁴ The chromate that is the most soluble in water at 25 °C on a molar basis is:

• Ag₂CrO₄
• BaCrO₄
• PbCrO₄
• none of these

Solution

The salt with more K_sp is more soluble in water. Hence BaCrO₄ is more soluble.

Q26. A mixture of CH₃COOH and CH₃COONa behaves as

• Acidic buffer
• Basic buffer
• Neutral buffer
• Ionic buffer

Solution

A mixture of weak acid and its salt with a strong base serves as an acidic buffer

Q27. In which of the following reaction can equilibrium be attained?

• Reversible reaction
• Irreversible reaction
• Cyclic reaction
• Decomposition reaction

Solution

Equilibrium can be attained in reversible reaction.

Q28. How will addition of catalyst affect the equilibrium of a reaction

• Equilibrium will shift in the forward direction
• Equilibrium will shift in the backward direction
• There will be no effect on equilibrium
• It will sometimes shift in forward and sometimes in backward direction

Solution

There will be no effect on equilibrium.

Q29. The molar solubility of PbBr₂ is 2.17 x 10^-3 M at a certain temperature. Calculate K_sp for PbBr₂

• 6.2 x 10^-6
• 6.4 x 10^-7
• 4.1 x 10^-8
• 3.4 x 10⁶

Solution

For AB₂/A₂B type salt, K_sp = 4S³

Q30. Which of the following is an example of basic buffer?

• A mixture of NH₄Cl and NH₄OH
• A mixture of CH₃COOH and OH₃COONa
• A mixture of HCl and NaOH
• 1M solution of NaOH

Solution

A mixture of weak base and its salt with a strong acid serves as a basic buffer.

Q31. The process based upon Henry's law is

• Dissolution of gases in liquid at high pressure
• Dissolution of gases and its solution in liquid at high pressure
• Intermixing of gases into each other
• None of the above

Solution

According to Henry's law the mass of gas that dissolves in a given mass of solvent at any temperature is directly proportion to its pressure of the gas above the surface of the solvent.

Q32. For the reversible reaction : N_2(g) + 3H_2(g)⇌ 2 NH_3(g) + heat The equilibrium shifts in forward direction :

• By increasing the concentration of NH_3(g)
• By decreasing the pressure
• By decreasing the concentration of N_2(g) and H_2(g)
• By increasing pressure and decreasing temperature

Solution

According to the Le Chatelier’s principle, the equilibrium shifts in the forward direction by increasing pressure and decreasing temperature. 

Q33. Which of the following characterizes equilibrium?

• Dynamic nature
• Requires a closed system
• Can be physical or chemical
• All of the above

Solution

Equilibrium is attained in the closed system. It can be physical or chemical and is dynamic.

Q34. Which of the following is a correct statement?

• All Bronsted bases are Arrhenius bases.
• All Bronsted acids are Arrhenius acids.
• All Lewis acids are Arrhenius acids.
• All Lewis bases are Arrhenius bases.

Solution

According to both Arrhenius and Bronsted concept, acids are proton donors.

Q35. pH of a buffer solution is

• 1
• 7
• 9
• Varies with the type of buffer

Solution

pH of a buffer solution varies with the type of buffer

Q36. Which of the following solutions has the lowest pH at 25^oC?

• 0.2 M sodium hydroxide
• 0.2 M acetic acid
• 0.2 M ammonia
• 0.2 M benzoic acid

Solution

Benzoic acid is most acidic so it will show the lowest pH at 25 °C.

Q37. One mole of N₂ and 3 moles of H₂ are mixed in a litre flask. If 50% of N₂ is converted into ammonial by the reaction, N_{2 (g)} + 3 H_{2 (g)} → 2 NH_{3 (g)} then the total number of moles of gas equilibrium will be

• 1
• 1.5
• 2
• 3

Solution

Total No. of moles at equilibrium is 0.5 N₂ + 1.5 H₂ + 1 NH₃ = 3 moles

Q38. What is the K_sp expression for the salt PbI₂?

• [Pb²⁺][I^-]²
• [Pb²⁺][2I^-]
• [Pb²⁺][I₂]²
• [Pb²⁺][2I^-]²

Solution

PbI₂  Pb²⁺ + 2I^- or, K_sp = [Pb²⁺][2I^-]²

Q39. Which of the following is correct for pH?

• Its value can be negative
• It is the difference of kw and pOH
• It is a measure of acidic and basic strength
• All of the above

Solution

pH is a measure of acidic and basic strength. It can be calculated by taking difference between and pOH. Its value can be negative for highly acidic solutions.

Q40. When in a saturated solution of NaCl, HCl is passed, pure precipitate of NaCl is formed. This is due to the fact:

• That solubility of NaCl decreases
• That HCl is highly soluble in water
• That the ionic product of NaCl exceeds the solubility product of NaCl.
• That HCl is strong acid