In a 3 molal solution, how many moles of solute are needed for 500 g solvent?
Answer and explanation
Correct answer: 1.5 mole
A 3 molal solution contains 3 moles of solute for every 1 kg of solvent. Convert the given solvent mass: 500 g = 0.5 kg. The required amount is therefore n = m × mass of solvent in kg = 3 mol kg−1 × 0.5 kg = 1.5 mol. Option A is correct. Three moles would require 1 kg solvent, not 500 g, so option B doubles the required amount.
Frequently asked questions
What is the correct answer to this question?
1.5 mole
Why is this the correct answer?
A 3 molal solution contains 3 moles of solute for every 1 kg of solvent. Convert the given solvent mass: 500 g = 0.5 kg. The required amount is therefore n = m × mass of solvent in kg = 3 mol kg−1 × 0.5 kg = 1.5 mol. Option A is correct. Three moles would require 1 kg solvent, not 500 g, so option B doubles the required amount.
Which subject and chapter does this question cover?
This is a Class 11 Chemistry question. Chapter: Chapter 01: Solutions.
