Question

1. A 5.05 g sample of quartz (SiO2) contains 2.36 g of silicon. What are the percentages of silicon

Answer 1

Answer: B) 46.7% Si and 53.3% O

Explanation:

To calculate the mass percent of element in a given compound, we use the formula:

$\text{Mass percent of element}=\frac{\text{Mass of element}}{\text{total mass}}\times 100\%$

Mass of quartz  $(SiO_2)$ = 5.05 g

Mass of silicon = 2.36 g

Mass of oxygen = Mass of quartz  $(SiO_2)$ - mass of silicon = 5.05g - 2.36 g = 2.69 g

$\text{Mass percent of silicon}=\frac{\text{Mass of silicon}}{\text{total mass of quartz}}\times 100=\frac{2.36}{5.05}\times 100=46.7\%$

$\text{Mass percent of oxygen}=\frac{\text{Mass of oxygen}}{\text{total mass of quartz}}\times 100=\frac{2.69}{5.05}\times 100=53.3\%$

Thus the percentages of silicon and oxygen in quartz are B) 46.7% Si and 53.3% O