For the reaction 2HNO3 + Mg(OH)2 → Mg(NO3) 2 + 2H2O, how many grams of magnesium nitrate are produced from 4 grams of nitric acid, HNO3 ?

Question

Round your answer to the nearest tenth. Do not round your answers until the last step of the problem. If you do, the computer might mark your answer incorrect and you will be asked to complete your second trial for this assessment.

Use the following molar masses:

Element	Molar Mass
Hydrogen	1
Magnesium	24
Nitrogen	14
Oxygen	16

Answer 1

2HNO3 + Mg(OH)2 ==> Mg(NO3)2 + 2H2O .. balanced equation

molar mass HNO3 (nitric acid) = 1 + 14 + (16 x 3) = 63 g / mol

molar mass Mg(NO3)2 (magnesium nitrate) = 24 + (14x2) + (16x6) = 148 g / mol

Using the stoichiometry of the balanced equation and dimensional analysis, we can find our answer:

4 g HNO₃ x 1 mol HNO₃ / 63 g x 1 mol Mg(NO₃)₂ / 2 mol HNO₃ x 148 g Mg(NO₃)₂ / mol = 1.17 g Mg(NO₃)₂

Rounding this answer to the nearest tenth gives us 1.2 g Mg(NO₃)₂