COMEDK · Chemistry · 17. Solutions

An aqueous solution of an unknown solute "X" is prepared by adding 4.0g of it into 2.0moles of water. What is the mass percent of "X" in the aqueous solution?

A \(40\)
B \(20\)
C \(10\)
D \(15\)

Verified Solution

Answer & Solution

Correct Answer

(C) \(10\)

Step-by-step Solution

Detailed explanation

Mass of solute \(X = 4.0\) g Moles of water \(= 2.0\) mol Molar mass of water \(= 18\) g/mol Mass of water \(= 2.0 \times 18 = 36.0\) g Total mass of solution \(= 4.0 + 36.0 = 40.0\) g Mass percent of \(X = \left( \dfrac{4.0}{40.0} \right) \times 100 = 10\) Answer: \(10\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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