Zinc metal reacts with yellow crystals of sulfur in a fiery reaction to produce a white powder of zinc sulfide. A chemist determines that 65.4 g of zinc reacts with 32.1 g of sulfur. How many grams of zinc sulfide could be produced from 20.0 g of zinc metal?

#### Solution:

### We can use the law of conservation of mass to figure out how many grams of zinc sulfide could be produced. We can write the following:

### Mass of zinc + mass of sulfur = mass of zinc sulfide

### Thus, we can write:

### m_{ZnS}=65.4g+32.1g

### m_{ZnS}= 97.5g

### To figure out how many grams of zinc sulfide could be produced from 20.0 g of zinc metal, we can say that:

### 20.0 g + mass of sulfur = x (where x is the mass of zinc sulfide that can be produced)

### Using proportions, we can write:

### \frac{m_{Zn}}{m_{ZnS}}=\frac{65.4 g}{97.5 g}=\frac{20.0g}{x}

### x=29.81g