Acids and Bases Practice Questions
IB (International Baccalaureate) · IB Chemistry HL · 144 free MCQs with instant results and detailed explanations.
144
Total
44
Easy
74
Medium
26
Hard
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Sample Questions from Acids and Bases
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Q1
Easy
Which of the following statements correctly defines a Brønsted-Lowry acid?
A.
A substance that accepts protons.
B.
A substance that donates protons.
C.
A substance that increases hydroxide ion concentration in solution.
D.
A substance that increases hydronium ion concentration in solution.
Show Answer & Explanation
Correct Answer: B
A Brønsted-Lowry acid is defined as a substance that donates protons (H+ ions) to another substance, making option B correct.
Q2
Easy
Which of the following solutions would have the highest pH?
A.
0.1 M HCl
B.
0.1 M NaOH
C.
0.01 M H2SO4
D.
1.0 M NH4Cl
Show Answer & Explanation
Correct Answer: B
0.1 M NaOH is a strong base which will give a high pH. The other solutions, being acids or neutral salts, will have lower pH values.
Q3
Easy
What is the conjugate base of H2O when it acts as an acid?
A.
OH-
B.
H3O+
C.
H2O2
D.
H+
Show Answer & Explanation
Correct Answer: A
When H2O donates a proton (H+), it becomes OH-, which is its conjugate base. Therefore, option A is correct.
Q4
Medium
What is the pH of a 0.1 M hydrochloric acid solution?
A.
1
B.
0.1
C.
0
D.
2
Show Answer & Explanation
Correct Answer: A
Hydrochloric acid (HCl) is a strong acid that dissociates completely in water. Therefore, a 0.1 M solution of HCl yields a hydrogen ion concentration of 0.1 M. The pH is calculated using the formula pH = -log[H+]. Thus, pH = -log(0.1) = 1.
Q5
Medium
Which of the following statements correctly describes a buffer solution?
A.
It resists changes in pH when small amounts of acid or base are added.
B.
It has a pH of exactly 7.
C.
It can only be made from weak acids.
D.
It is always a neutral solution.
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Correct Answer: A
A buffer solution is specifically designed to resist changes in pH upon the addition of small amounts of acids or bases. This property is due to the presence of weak acids and their conjugate bases (or weak bases and their conjugate acids) that can react with added H+ or OH- ions.
Q6
Medium
A 0.5 M solution of acetic acid has a pH of approximately 2.87. What is the dissociation constant (Ka) for acetic acid?
A.
1.76 × 10^-5
B.
1.0 × 10^-14
C.
5.0 × 10^-5
D.
1.0 × 10^-7
Show Answer & Explanation
Correct Answer: A
To find the dissociation constant (Ka) for acetic acid, we first determine the concentration of H+ ions from the pH (which is 0.00134 M). Using the formula Ka = [H+][A-]/[HA], we find [A-] = [H+] and [HA] can be calculated as 0.5 - [H+]. Thus, Ka = (0.00134)(0.00134)/(0.5 - 0.00134) which approximates to 1.76 × 10^-5.
Q7
Medium
Which of the following acids would be expected to have the highest pKa value?
A.
Hydrochloric acid (HCl)
B.
Acetic acid (CH3COOH)
C.
Nitric acid (HNO3)
D.
Formic acid (HCOOH)
Show Answer & Explanation
Correct Answer: B
pKa is inversely related to acid strength; the higher the pKa, the weaker the acid. Among the given options, acetic acid is the weakest acid (compared to HCl, HNO3, and HCOOH), which means it has the highest pKa value.
Q8
Hard
What is the pH of a solution that has a hydrogen ion concentration of 1.0 x 10^-4 mol/L?
A.
4
B.
3
C.
10
D.
7
Show Answer & Explanation
Correct Answer: A
The pH is calculated using the formula pH = -log[H+]. Here, [H+] = 1.0 x 10^-4, so pH = -log(1.0 x 10^-4) = 4. This indicates that the solution is acidic.
Q9
Hard
A buffer solution is made by mixing equal volumes of 0.1 M acetic acid (CH3COOH) and 0.1 M sodium acetate (CH3COONa). What is the pH of this buffer solution? (pKa of acetic acid = 4.76)
A.
4.76
B.
5.76
C.
3.76
D.
6.76
Show Answer & Explanation
Correct Answer: A
According to the Henderson-Hasselbalch equation, pH = pKa + log([A-]/[HA]). Since equal volumes of acetic acid and sodium acetate are mixed, [A-] = [HA], making the log term equal to 0. Thus, pH = pKa = 4.76.
Q10
Hard
Which of the following statements correctly describes the behavior of strong acids and strong bases in aqueous solution?
A.
Strong acids completely dissociate into ions, while strong bases partially dissociate.
B.
Both strong acids and strong bases completely dissociate into their respective ions.
C.
Strong acids and bases have no effect on the pH of the solution.
D.
Strong acids are weak electrolytes, while strong bases are strong electrolytes.
Show Answer & Explanation
Correct Answer: B
Strong acids, such as HCl, and strong bases, such as NaOH, fully dissociate into ions in aqueous solutions, resulting in a higher conductivity and significant changes in pH.
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Acids and Bases — IB (International Baccalaureate) IB Chemistry HL Practice Questions Online
This page contains 144 practice MCQs for the chapter Acids and Bases in IB (International Baccalaureate) IB Chemistry HL. The questions are organized by difficulty — 44 easy, 74 medium, 26 hard — so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit.