Final answer:
A 20% (m/m) solution contains 20 grams of solute per 100 grams of the solution, not the solvent, making the Assertion incorrect and the Reason correct. The answer is D) A is wrong, and R is correct.
Step-by-step explanation:
The question presented involves understanding percentages in mass/mass solutions within the subject of chemistry. When discussing a 20% (m/m) solution, it means that there are 20 grams of solute in every 100 grams of the solution, and not just the solvent. Therefore, a 20% (m/m) solution actually contains 20 grams of solute and 80 grams of solvent to make up a total of 100 grams of solution.
Given the definitions, the correct answer here is D) A is wrong, and R is correct. In the case of the 20% (m/m) solution, the Assertion is incorrect because it implies that the 100 grams refers to the solvent only, instead of the entire solution. The Reason is correct as it accurately reflects that 20 grams of solute are in the entire 100 grams of the solution.