Densityof a Gas at

STPLesson # 4

1. Calculate the density of N2 at STP.

Assume that youhave 1 mole of N2 22.4 L

28.0 g = 1.25 g/L

litregramsDensity =

2. Calculate the density of CO2 at STP.

Assume that youhave 1 mole of CO2 22.4 L

44.0 g = 1.96 g/L

litregramsDensity =

3. Calculate the molar mass of gas that weighs 0.2668 g and has a STP molar volume of 175.7 mL. If the gas can be found in Harrison Hot Spring water, determine the gas.

x 1 L175.7 mL = 0.0078438 mol

molegramsMolar Mass =

1000 mL x 1 mol

22.4 L

0.0078438 mol0.2668 gMolar Mass =

= 34.01 g/mol = H2S

4. Calculate the volume of O2 gas produced at STP for the complete decomposition of 12.5 g HgO if the yield is 45.0 %.

2HgO → 2Hg + O2

= 0.291 L x 0.4501 mole

x 22.4 Lx 1 mole O2

2 mole HgOx 1mole12.5 g HgO

216.6 g

12.5 g ? L12

5. Calculate the theoretical yield in litres at STP of CO2 in the reaction of 100. g of Fe2O3. If the actual yield was 19.0 L @

STP, calculate the percentage yield.

2Fe2O3+ 3C 4Fe + 3CO2

100. g Fe2O3 x 1 mole x 3 mole CO2 x 22.4 L = 21.0 L

159.6 g 2 mole Fe2O3 1 mole

Percentage yield = 19.0 L x 100% = 90.3 %21.05 L

32

100. g ? L

19.0 L