Chemistry Multiple Choice Questions on “Equilibrium – Ionization of Acids and Bases”.
1. What is the value of the ionic product of water at 298k?
a) 7 x 10-14/mol2L2
b) 1 x 10-10/mol2L2
c) 1 x 10-14/molL2
d) 1 x 10-14/mol2L2
Answer: d
Clarification: Ionic product is a product of the concentration of hydronium ions and hydroxyl ions in pure water, which remains constant at a particular temperature. It is symbolized as KW and is equal to 1 x 10-14/mol2L2.
2. The ionization constant of water increases with increase in temperature.
a) true
b) false
Answer: a
Clarification: The ionization product of water is given by [H3O+][OH–] = 1 x 10-14/mol2L2 at 298 k, the product of the concentration of hydronium ions and hydroxyl ions in pure water. Concentrations increase with temperature, so the ionization constant of water increases with increase in temperature.
3. Write pH in terms of concentration of hydrogen ion?
a) [H+] = 1-pH
b) [H+] = 10-pH
c) [H+] = 10pH
d) [H] = 10-pH
Answer: b
Clarification: pH is defined as the negative logarithm of hydrogen ion concentration that is pH = -log[H+]. By rearranging pH in terms of concentration of hydrogen ions, we get [H+] = 10-pH. pH means potential of hydrogen.
4. What is the pKW at 298 k?
a) 14
b) 7
c) 1
d) 0
Answer: a
Clarification: We know that the ionization constant of water at 298 k is given by [H3O+][OH–] = 1 x 10-14/mol2L2. pKW = pH + pOH = -log[H3O+] – log[OH–] = -log[H3O+][OH–] = -log10-14 = log1014 = 14. Therefore pKW at 298 k is 14.
5. Which of the following has a PH greater than 7?
a) gastric juice
b) vinegar
c) blood plasma
d) lemon juice
Answer: c
Clarification: Acids always have a pH below 7 and bases have a pH of above 7, while neutral compounds have a pH of 7. Here gastric juice, vinegar, and lemon are acids, so they have a pH of below 7, but blood plasma is a base. It has a pH greater than 7.
6. A neutralization reaction results in the formation of _______________
a) salts
b) acid
c) base
d) hydrogen
Answer: a
Clarification: Salts are the products of the reaction between an acid and a base, these type of reactions are called neutralization reactions. There are many types of salts like normal, acidic, basic, double, complex and mixed salts.
7. NaCl is a ________ salt.
a) Normal
b) Acidic
c) Basic
d) Double
Answer: a
Clarification: Normal salts like NaCl are obtained by complete neutralization of an acid with a base. Acidic salts are formed by incomplete neutralization of polybasic acids and basic salts are formed by incomplete neutralization of poly acidic base. Double salts are formed by the combination of two simple salts and exist only in the solid state.
8. What is the reverse process of Neutralization?
a) formation
b) hydrolysis
c) reaction
d) splitting
Answer: b
Clarification: Salts are strong electrolytes and on dissolution in water split up into ions. Which react with hydrogen ions are Hydroxide ions furnished by water yielding an acidic or basic solution. This process is called salt hydrolysis and is the reverse process of neutralization.
9. Why is the aqueous solution of a salt of a weak acid and strong base is alkaline?
a) utilization
b) neutralization
c) cationic hydrolysis
d) anionic hydrolysis
Answer: d
Clarification: The aqueous solution of a salt of a weak acid and strong base is alkaline, due to the anionic hydrolysis and aqueous solution of a salt of a strong acid and weak base is acidic, due to cationic hydrolysis with dilution degree of hydrolysis increases.
10. What is the hydrolysis constant of a weak acid-weak base?
a) KW/Kb
b) KW/Ka
c) KW/KaKb
d) 1/KaKb
Answer: c
Clarification: The hydrolysis constant of a weak acid and weak base is KW/KaKb, the degree of hydrolysis is √KW/KaKb and the pH of the solution is given by 1/2pKW + 1/2pKa – 1/2pKb. An example of a salt of a weak acid and a weak base is CH3COOHNH4.
11. Formic acid has a concentration of 0.1M and Ka is 1.77 x 10-4. What is the value of degree of dissociation?
a) 4
b) 4.2
c) 0.42
d) 42
Answer: b
Clarification: The dissociation constant K = [H+][HCOO–]/[HCOOH] = x2/0.1 – x = 1.77 x 10-4; x = [H+] = 0.0042M. The percent of dissociation is x/0.1 = (0.042M)100% = 4.2. Therefore the value of degree of dissociation is 4.2
12. What is the pH of the solution of sulphuric acid having a concentration of 0.01M?
a) 1
b) 2
c) 3
d) 4
Answer: b
Clarification: pH is defined as the negative logarithm of hydrogen ion concentration that is pH = -log[H+]. So here, the pH of the solution of sulphuric acid is -log[H+], where concentration of hydrogen ion is 0.01M = -log[10-2] = 2.
13. Acetic acid’s pKa is 4.2 and ammonium hydroxide pKb is 3.24. What is the pH of the ammonium acetate solution?
a) 7.12
b) 7
c) 4.2
d) 7.48
Answer: d
Clarification: We know that the pH of the solution of a weak acid and a weak base is given by 1/2pKW + 1/2pKa – 1/2pKb. So pH = 7 + (frac{1}{2})[4.2 – 3.24]; pH = 7 + 0.48 = 7.48, we get this by substituting acetic acid’s pKa as 4.2 and ammonium hydroxide pKb as 3.24.
14. Acid strength increases in the order of _____________
a) HF ≪ HCl ≪ HBr ≪ HI
b) HF ≪ HBr ≪ HCl ≪ HI
c) HI ≪ HCl ≪ HBr ≪ HF
d) HCl ≪ HF ≪ HBr ≪ HI
Answer: a
Clarification: The correct order of increase in acidic strength is HF ≪ HCl ≪ HBr ≪ HI. There are many factors affecting acid strength. Hear the hydrogen-acid Bond strength decreases, as the acid strength increases.