Chemistry · Some Basic Concepts of Chemistry (Mole Concept) + Stoichiometry

NEET (UG) 2024 — Question 82

1 gram of sodium hydroxide was treated with 25 mL of 0.75 M HCl solution, the mass of sodium hydroxide left unreacted is equal to

Option A:
750 mg
Option B:
250 mg
Correct
Option C:
Zero mg
Option D:
200 mg

Answer: B

Step-by-step solution

Moles of HCl = $0.75 \times 0.025 = 0.01875 \, \text{mol}$ . Mass of HCl = $0.01875 \times 36.5 = 0.684 \, \text{g}$ . Reaction: $\ce{HCl + NaOH -> NaCl + H2O}$ . 1 mol HCl reacts with 1 mol NaOH, so moles of NaOH consumed = 0.01875 mol. Mass of NaOH consumed = $0.01875 \times 40 = 0.750 \, \text{g}$ . Mass of NaOH left unreacted = $1 - 0.750 = 0.250 \, \text{g} = 250 \, \text{mg}$ . Therefore, the correct answer is B.

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Exam: NEET (UG) 2024
Paper: 2024 paper
Subject: Chemistry
Chapter: Some Basic Concepts of Chemistry (Mole Concept) + Stoichiometry
Topic: Acid-Base Titrations and Related Problems

Answer: B

Step-by-step solution

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