Question

what is the molar mass of mgo? 40.003 g/mol 48.610 g/mol 45.255 g/mol 40.304 g/mol

Explanation:

Step1: Find atomic masses

Atomic mass of Mg: $24.305\ \text{g/mol}$, O: $16.00\ \text{g/mol}$ (approximate, or more precisely O is $15.9994\ \text{g/mol}$).

Step2: Sum atomic masses

Molar mass of MgO = atomic mass of Mg + atomic mass of O.
Using precise values: $24.305 + 15.9994 = 40.3044\ \text{g/mol}$, which rounds to $40.304\ \text{g/mol}$.

Answer:

40.304 g/mol (corresponding to the red option: 40.304 g/mol)