Question

± Stoichiometric Relationships with Gases

The ideal gas law

PV=nRT

relates pressure P, volume V, temperature T, and number of moles of a gas, n. The gas constant Requals 0.08206 L⋅atm/(K⋅mol) or 8.3145 J/(K⋅mol). The equation can be rearranged as follows to solve for n:

n=PVRT

This equation is useful when dealing with gaseous reactions because stoichiometric calculations involve mole ratios.

Part A

When heated, calcium carbonate decomposes to yield calcium oxide and carbon dioxide gas via the reaction

CaCO3(s)→CaO(s)+CO2(g)

What is the mass of calcium carbonate needed to produce 61.0 L of carbon dioxide at STP?

Express your answer with the appropriate units.

mass of CaCO3 =

Part B

Butane, C4H10, is a component of natural gas that is used as fuel for cigarette lighters. The balanced equation of the complete combustion of butane is

2C4H10(g)+13O2(g)→8CO2(g)+10H2O(l)

At 1.00 atm and 23 ∘C, what is the volume of carbon dioxide formed by the combustion of 2.60 g of butane?

Express your answer with the appropriate units.

volume of CO2 =

Answer 1

A)
At STP,
mol of CO2 = volume of CO2/22.4 L
= 61.0/22.4
= 2.723 mol

from reaction,
mol of CaCO3 required = mol of CO2 formed
= 2.723 mol

mass of CaCO3 = number of mol * molar mass
= 2.723 mol * 100 g/mol
= 272 g

Answer: 272 g

B)
number of mol of C4H10 = mass/molar mass
= 2.60 g / (58 g/mol)
= 0.0448 mol

mol of CO2 formed = 4 times mol of C4H10 reacted
= 4*0.0448 mol
= 0.1792 mol

P = 1.00 atm
T= 23 oC = (23+273 ) K = 296 K

use:
P*V = n*R*T
1*V = 0.1792*0.0821*296
V = 4.35 L

Answer: 4.35 L