Acid–base titrations Knowledge-Based Download PDF

Questions

1. 1.

   A 0.375 g sample of an unknown pure monoprotic acid is dissolved in water and completely neutralized by 30.0 mL of a 0.125 M $\text{NaOH}$ solution. What is the molar mass of the acid?

   • A) 100 g/mol
   • B) 50.0 g/mol
   • C) 150 g/mol
   • D) 200 g/mol
2. 2.

   An acid–base titration of a weak monoprotic acid with a strong base produces an equivalence point at pH = 8.7. Which of the following indicators is most suitable for detecting the end point of this titration?

   • A) Phenolphthalein (pH transition range 8.2–10.0)
   • B) Methyl red (pH transition range 4.4–6.2)
   • C) Bromocresol green (pH transition range 3.8–5.4)
   • D) Thymol blue in its acidic range (pH transition range 1.2–2.8)
3. 3.

   A 40.0 mL sample of 0.100 M hydrochloric acid ($\text{HCl}$) is titrated with 0.100 M sodium hydroxide ($\text{NaOH}$) at 25 °C. What is the pH of the solution after the addition of 60.0 mL of the $\text{NaOH}$ titrant?

   • A) 1.70
   • B) 7.00
   • C) 12.00
   • D) 12.30
4. 4.

   A 40.0 mL sample of 0.150 M aqueous ammonia ($\text{NH}_3$, $K_b = 1.8 \times 10^{-5}$) is titrated with 0.150 M hydrochloric acid ($\text{HCl}$). What is the pH of the solution after the addition of 20.0 mL of the $\text{HCl}$ titrant?

   • A) 4.74
   • B) 7.00
   • C) 9.26
   • D) 11.22
5. 5.

   A 50.0 mL sample of 0.100 M acetic acid ($\text{CH}_3\text{COOH}$, $K_a = 1.8 \times 10^{-5}$) is titrated with 0.100 M sodium hydroxide ($\text{NaOH}$). What is the pH of the solution at the equivalence point?

   • A) 8.72
   • B) 7.00
   • C) 5.28
   • D) 4.74