What is the mass of NaCl required to prepare 140 grams of a 12% (by mass) NaCl solution in water?

• A. 28 grams
• B. 12 grams
• C. 127.2 grams
• D. 16.8 grams

Answer: (D)

Verified step by step guidance

1. Understand that a 12% (by mass) NaCl solution means 12 grams of NaCl are present in every 100 grams of solution.
2. Set up the relationship using the percentage by mass formula: \(\text{mass \%} = \frac{\text{mass of solute}}{\text{mass of solution}} \times 100\).
3. Let the mass of NaCl be \(m\). Using the formula, write the equation: \$12 = \frac{m}{140} \times 100$.
4. Rearrange the equation to solve for \(m\): \(m = \frac{12 \times 140}{100}\).
5. Calculate \(m\) to find the mass of NaCl required to prepare 140 grams of a 12% NaCl solution.