200 mL of 3 M acid is mixed with 400 mL of 1.5 M same acid. Assuming final volume is 600 mL what is the molarity?
Answer and explanation
Correct answer: 2.0 M
For mixing the same solute, add the moles contributed by each solution and divide by the stated final volume. First solution: n = 3 × 0.200 = 0.600 mol. Second solution: n = 1.5 × 0.400 = 0.600 mol. Total moles = 1.200 mol; final volume = 600 mL = 0.600 L. Therefore M = 1.200/0.600 = 2.0 M, so option B is correct. Options based on averaging concentrations without volume weighting are incorrect.
Frequently asked questions
What is the correct answer to this question?
2.0 M
Why is this the correct answer?
For mixing the same solute, add the moles contributed by each solution and divide by the stated final volume. First solution: n = 3 × 0.200 = 0.600 mol. Second solution: n = 1.5 × 0.400 = 0.600 mol. Total moles = 1.200 mol; final volume = 600 mL = 0.600 L. Therefore M = 1.200/0.600 = 2.0 M, so option B is correct. Options based on averaging concentrations without volume weighting are incorrect.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Some Basic Concepts of Chemistry. Topic: Mole concept and molar mass.
