Question

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

and oxygen in quartz?
A) 53.3% Si and 46.7% 0
B) 46.7% Si and 53.3% 0
C) 29.9% Si and 70.1% 0
D) 70.1% Si and 29.9% 0
E) 46.7% Si, and insufficient information to calculate %O

Answer 1

Answer: B) 46.7% Si and 53.3% O

Step-by-step 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}}* 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}}* 100=(2.36)/(5.05)* 100=46.7\%`

`\text{Mass percent of oxygen}=\frac{\text{Mass of oxygen}}{\text{total mass of quartz}}* 100=(2.69)/(5.05)* 100=53.3\%`

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