An alloy of metals X and Y weighs 12 g and contains atoms X and Y in the ratio of 2:5. The percentage by mass of X in the sample is 20. If atomic mass of X is 40, what is the atomic mass of metal Y?

Explanation

To solve the problem, we will follow these steps:

### Step 1: Determine the mass of metal X in the alloy.
Given that the alloy weighs 12 g and contains 20% of metal X by mass, we can calculate the mass of metal X as follows:

\[ \text{Mass of X} = \frac{20}{100} \times 12 \, \text{g} = 2.4 \, \text{g} \]
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