Question

2Mg + O2 mc019-1.jpg 2MgO

Niven wants to calculate the mass of MgO that is produced by the burning of 28.0 g of Mg. What is the first step in Niven’s calculation?
Balance the chemical equation.
Convert grams of Mg to moles.
Determine whether heat is given off by this reaction.
Find the number of Mg atoms in the sample.

Answer 1

The answer is b, convert grams of Mg to moles.

Step-by-step explanation:

Answer 2

In order to compute the mass of MgO formed, Niven must first convert grams of Mg to moles.
The chemical reaction equation provides a ratio between the moles of magnesium and magnesium oxide. Thus, in order to determine the amount of MgO formed, the amount of Mg reacted must be known.

Solving:
Moles Mg = 28 / 24 = 1.17

Moles of MgO = 1.17
Mass of MgO = 1.17 * 40.3
Mass of MgO = 47.2 grams