How much water should be added to 300 g of a 20 percent solution to make the mass percent 12?
Answer and explanation
Correct answer: 200 g
The original solution contains 20% of 300 g = 60 g solute. Adding water changes the total mass but does not change the solute mass. If x g water is added, the final mass is 300 + x, and the required condition is 60/(300 + x) = 0.12. Thus 300 + x = 500, giving x = 200 g. Therefore option C is correct; 500 g is the final solution mass, not the amount of water added.
Frequently asked questions
What is the correct answer to this question?
200 g
Why is this the correct answer?
The original solution contains 20% of 300 g = 60 g solute. Adding water changes the total mass but does not change the solute mass. If x g water is added, the final mass is 300 + x, and the required condition is 60/(300 + x) = 0.12. Thus 300 + x = 500, giving x = 200 g. Therefore option C is correct; 500 g is the final solution mass, not the amount of water added.
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.
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