Question

what is the percent composition of magnesium (mg) in mgo?
a. 70%
b. 40%
c. 50%
d. 60%

Explanation:

Step1: Find atomic masses

The atomic mass of Mg is approximately 24 g/mol and of O is approximately 16 g/mol.

Step2: Calculate molar - mass of MgO

The molar - mass of MgO, $M_{MgO}=M_{Mg}+M_{O}=24 + 16=40$ g/mol.

Step3: Calculate percent composition of Mg

The percent composition of Mg in MgO is $\frac{M_{Mg}}{M_{MgO}}\times100\%=\frac{24}{40}\times100\% = 60\%$.

Answer:

D. 60%