Question

silicon (si) exists in earths crust as sio₂. calculate the percent composition by mass of o and si in sio₂. round your answer to 4 significant digits. part 1 of 2 53.26 %o part 2 of 2 46.74 %si

Explanation:

Step1: Determine molar masses

The molar mass of Si is $M_{Si}=28.09\ g/mol$, and the molar mass of O is $M_{O} = 16.00\ g/mol$. For $SiO_{2}$, the molar mass $M = M_{Si}+2\times M_{O}=28.09 + 2\times16.00=28.09 + 32.00 = 60.09\ g/mol$.

Step2: Calculate mass - percent of O

The mass - percent of O in $SiO_{2}$ is $\text{mass}\%_{O}=\frac{2\times M_{O}}{M}\times100\%=\frac{2\times16.00}{60.09}\times100\%=\frac{32.00}{60.09}\times100\%\approx53.26\%$.

Step3: Calculate mass - percent of Si

The mass - percent of Si in $SiO_{2}$ is $\text{mass}\%_{Si}=\frac{M_{Si}}{M}\times100\%=\frac{28.09}{60.09}\times100\%\approx46.74\%$.

Answer:

The percent composition by mass of O in $SiO_{2}$ is 53.26% and of Si is 46.74%.