Question

What quantity of \(\text{H}_2\text{O}\) in gram is present in \(0.25\) mol of it?

• A. \(4.5\) g
• B. \(0.25\) g
• C. \(18\) g
• D. \(5.4\) g

Hint:

Mass equals moles times molar mass, and the molar mass of water is 18 g per mol.

Answer 1

The Correct Option is A

Step 1: Method:
Use the proportion: 1 mol of water weighs 18 g, so 0.25 mol weighs one quarter of that.

Step 2: Working:
$0.25 = \tfrac14$, so $18 \div 4 = 4.5$ g.

Step 3: Eliminate:
18 g is a whole mole. 0.25 g and 5.4 g do not match 18 g times 0.25. Only 4.5 g fits, option (A).

Final Answer:
The mass is 4.5 g, option (A). \[ \boxed{\text{(A) } 4.5\ \text{g}} \]