Question

How many grams of magnesium chloride will be produced when 7.9 x 10^23 molecules of magnesium are used as a reactant?
Remember to use three decimal places and NO units in your answer.

Mg + HCl → MgCl2 + H2

Molar masses (g/mol): H = 1; Mg = 24; Cl = 35.5

Answer 1

%H=

mass compound

mass H

100%

%C=

mass compound

mass C

×100%

If analysis of a 10.0-g sample of this gas showed it to contain 2.5 g H and 7.5 g C, the percent composition would be calculated to be 25% H and 75% C:

%H=10.0g compound

2.5g H

×100%=25%

C=10.0g compound

7.5g C

×100%=75%

%C=

12.04g compound

7.34g C

×100%=61.0%

%H=

12.04g compound

1.85g H

×100%=15.4%

%N=

12.04g compound

2.85g N

×100%=23.7%

The analysis results indicate that the compound is 61.0% C, 15.4% H, and 23.7% N by mass.