Question

a solution is prepared by dissolving 45 g of salt in 318 g of water. what is the mass percent of salt? 31 × % m/m submit question

Explanation:

Step1: Find total mass of solution

Total mass = mass of salt + mass of water = \( 45\,\text{g} + 318\,\text{g} = 363\,\text{g} \)

Step2: Calculate mass percent of salt

Mass percent formula: \( \text{Mass}\,\text{percent} = \frac{\text{Mass of solute}}{\text{Total mass of solution}} \times 100 \)
Substitute values: \( \frac{45}{363} \times 100 \approx 12.4\% \) (Wait, the initial input had 31 marked wrong. Let's recalculate correctly. \( \frac{45}{45 + 318}=\frac{45}{363}\approx 0.124 \), times 100 is \( 12.4\% \). But maybe the user's initial wrong answer was 31, let's do the steps properly.)

Wait, let's redo:

Step1: Calculate total mass

Salt mass = 45 g, water mass = 318 g. Total mass = 45 + 318 = 363 g.

Step2: Apply mass percent formula

Mass percent of salt = (mass of salt / total mass of solution) × 100 = (45 / 363) × 100 ≈ 12.4% (rounded to one decimal place) or more precisely, 45 ÷ 363 = 0.1239669..., ×100 = 12.396...% ≈ 12.4%

But maybe the problem was misread? Wait, maybe the water mass was 318? Let's check again. 45 + 318 = 363. 45/363 = 0.12396, so 12.4% approximately.

Wait, maybe the user's initial answer of 31 was incorrect. Let's do the calculation step by step.

Answer:

To find the mass percent of salt:

1. Total mass of solution: \( 45\,\text{g (salt)} + 318\,\text{g (water)} = 363\,\text{g} \).
2. Mass percent formula: \( \text{Mass}\,\text{percent} = \frac{\text{Mass of solute}}{\text{Total mass of solution}} \times 100 \).
3. Substitute values: \( \frac{45}{363} \times 100 \approx 12.4\% \).

(The initial "31" is incorrect. The correct mass percent of salt is approximately \( \boldsymbol{12.4\%} \) (or more precisely \( \approx 12.4\% \)).)