12.06g Mg and 7.94g O2
Work Step by Step
1) First, we need to write the chemical equation accordingly to the question. This question is similar to number 13. 2) Second, we need to convert 20g MgO into mol in order to do the calculation. Looking at the periodic table will tell us the molecular mass of MgO (sum of the molecular mass of Mg and O). According to our chemical equation, 1 mol of Mg will yield 1 mol of MgO. Convert mol of Mg into grams, we will know how much Mg needed to yield 20g MgO. 3) We'll apply the same method as we just did above for O2. Replace the molecular mass of Mg by O2, and you'll get the answer.