Question

Mg(OH)2 + 2 HBr à MgBr2 + 2 H2O

Answer the questions below based on the above reaction. Answer with the correct number of significant figures. Show your work! Each question is worth 8 points. 1 point for sig figs, 1 point for correct final unit, 3 points for correct final answer, 2 points for correct molar masses, and 1 point for dimensional analysis table.

1. How many grams of MgBr2 will be produced from 18.3 grams of HBr?

2. How many moles of H2O will be produced from 18.3 grams of HBr?

3. How many grams of Mg(OH)2 are needed to completely react with 18.3 grams of HBr?

Answer 1

Step-by-step explanation:

The balanced equation of the reaction is given as;

Mg(OH)2 (s) + 2 HBr (aq) → MgBr2 (aq) + 2 H2O (l)

1. How many grams of MgBr2 will be produced from 18.3 grams of HBr?

From the reaction;

2 mol of HBr produces 1 mol of MgBr2

Converting to masses using;

Mass = Number of moles * Molar mass

Molar mass of HBr = 80.91 g/mol

Molar mass of MgBr2 = 184.113 g/mol

This means;

(2 * 80.91 = 161.82g) of HBr produces (1 * 184.113 = 184.113g) MgBr2

18.3g would produce x

161.82 = 184.113

18.3 = x

x = (184.113 * 18.3 ) / 161.82 = 20.8 g

2. How many moles of H2O will be produced from 18.3 grams of HBr?

Converting the mass to mol;

Number of moles = Mass / Molar mass = 18.3 / 80.91 = 0.226 mol

From the reaction;

2 mol of HBr produces 2 mol of H2O

0.226 mol would produce x

2 =2

0.226 = x

x = 0.226 * 2 / 2 = 0.226 mol

3. How many grams of Mg(OH)2 are needed to completely react with 18.3 grams of HBr?

From the reaction;

2 mol of HBr reacts with 1 mol of Mg(OH)2

18.3g of HBr = 0.226 mol

2 = 1

0.226 = x

x = 0.226 * 1 /2

x = 0.113 mol