From 6 litres of a 5% salt solution, 1 litre of water evaporates. What is the new percentage of salt in the remaining solution?

Introduction / Context:
This concentration problem involves evaporation of solvent (water) only. Since salt does not evaporate, the mass of solute remains constant while the volume of solution decreases, raising the concentration. We compute the new percentage after evaporation.

Given Data / Assumptions:

• Initial volume = 6 L, salt concentration = 5%.
• Water loss due to evaporation = 1 L (solute unchanged).
• Final volume = 5 L.

Concept / Approach:
Amount of salt initially = 5% of 6 L = 0.05 * 6 = 0.30 L (in equivalent-volume terms). After evaporation, total solution volume is 5 L with the same 0.30 L salt. New percentage = (amount of salt / new volume) * 100%.

Step-by-Step Solution:

Verification / Alternative check:
If 5% of 6 L is 0.30 L, then in 5 L the same 0.30 L represents 6%, as 6% of 5 L equals 0.30 L. The logic is fully consistent.

Why Other Options Are Wrong:

• 5%: Would be true without evaporation; concentration must rise.
• 44/19% or 55/7%: These are inconsistent fractions for this setup, not matching 0.30/5.

Common Pitfalls:
Subtracting salt along with water or recalculating salt amount incorrectly. Only water evaporates, so the solute quantity remains fixed.

Final Answer: