Gas Stoich assignment

Question

2C2H2+5O2= 4CO2+2H2O Using the balanced equation : If you have 37.9 grams of C2H2 how many liters of carbon dioxide could be produced?

2C2H2+5O2=4Co2+2H2O If you have 130.0 liters of oxygen, how many grams of carbon dioxide could be produced?

Answer 1

2C2H2 + 5O2 => 4CO2 + 2H2O

molar mass C2H2 = 26 g / mol

37.9 g C2H2 x 1 mol / 26 g = 1.46 mols C2H2

1.46 mols C2H2 x 4 mols CO2 / 2 mol C2H2 = 2.92 mols CO2

At STP 1 mol of gas = 22.4 L

2.92 mols CO2 x 22.4 L / mol = 65.4 L CO2

2C2H2 + 5O2 => 4CO2 + 2H2O

molar mass CO2 = 44 g / mol

130 L O2 x 4 L CO2 / 5 L O2 = 104 L CO2

At STP: 104 L CO2 x 1 mol / 22.4 L = 4.64 mols CO2

4.64 mols CO2 x 44 g / mol = 204 g CO2

Answer 2

C2H2 (Ethylene) has a molecular weight of 26 = 2(12)+2(1)

Therefore 37.9 grams divided by the molecular weight is 1.76 gram moles = 37.9 grams / 26 gram moles

Using the balanced equation, there are 2 moles of C2H2 consumed per 4 moles of CO2 produced

2C2H2+5O2= 4CO2+2H2O

That means you produce 1.76 gram moles x 4 / 2 = 3.52 gram moles CO2

But the question asked for liters.

Let's use the ideal gas law. substituting the number of moles of CO2 produced for the "n" at standard temperature(273K) and pressure(1 atm).

PV - nRT

V= nRT/P = (3.52gram moles ) (0.082057 L atm / gram mole K) (273 K) / (1 atm) = 78.85 L

The second question is the same one as the first but in reverse.

2C2H2+5O2=4Co2+2H2O

130 liters Oxygen at standard temperature and pressure according to the ideal gas law.

PV = nRT converts to n = PV/RT

n = (1 atm) (130 liters) / (0.082057 L atm / gram mole K) (273 K)

n = 5.8 gram moles O₂

From the balanced equation... 5 moles of Oxygen are consumed per 4 moles of CO2 produced.

5.8 gram moles O₂ consumed x 4 moles of CO₂ produced / 5 moles of Oxygen consumed

4.64 gram moles CO2 produced

at 44.01 grams / gram mole

this gives a total of 204 grams CO2.

Ok we got some answers but do they make any sense?

Let's test them.

For the first problem 1.76 gram moles of C2H2 gets consumed. 2 moles of C2H2 are consumed per 4 moles CO2 produced. That leaves us with 3.52 gram moles of CO2 at STP and because we already know that at STP 22.4 liters per gram mole at STP. That checks out at 78.8 liters.

For the second problem, 130 liters / 22.4 l atm / gmol K = 5.8 gram moles oxygen consumed. With 5 moles oxygen consumed per 4 moles CO2 produced. That tells us we produced 4.64 gram moles or 204 grams of CO2. That checks out too.