Question

A) Butane combusts according to the equation: C4H10(g)+132O2(g)→4CO2(g)+5H2O(g) ΔHrxn=−2658kJ

- What mass of butane in grams is necessary to produce 1.1×10³ kJ kJ of heat? Express your answer to two significant figures and include the appropriate units.

- What mass of CO2 is produced? Express your answer to two significant figures and include the appropriate units.

B) Charcoal is primarily carbon. What mass of CO2 is produced if you burn enough carbon (in the form of charcoal) to produce 5.10×102kJ of heat? The balanced chemical equation is as follows:

C(s)+O2(g)→CO2(g),ΔH∘rxn=−393.5kJ

Express the mass in grams to three significant figures.

Answer 1

a)

HRxn = Q/n

Q = 1.1*10^3 kJ so

n = -Q/Hrxn =- (1.1*10^3)/(-2658) = 0.413844 mol needed

mass = mol*MW = 0.413844*58.12 = 24.052 g of butane -->2 sig fig --> 24 g butane

mol of CO2 produced = 0.413844 *4 = 1.655376 mol of CO2

mass = mol*MW = 1.655376*44 = 6.621504 g of CO2 --> 2 sig fig --> 6.6 g of CO2

B)

n = (5.1*10^2)/(393.5) = 1.2960 mol of C

mol of CO2 = 1.2960 mol of CO2

mass of CO2 = 1.2960*44 = 57.024 g of CO2 --> 3 sig fig --> 57.0 g of CO2