Question

Propane (C₃H₈) is used in domestic cooking and heating.

a) A typical home in Massachusetts burns 850 gal of propane for heating over the course of a year. How many moles of propane are burned?

(Some useful information you’ll need: density = 4.2 lb/ gal; 1 lb = 453.59 g)

b) Propane reacts with oxygen to produce carbon dioxide and water.

i) Write a balanced chemical equation for the reaction above.

ii) How many moles of carbon dioxide are released per home over the course of one year?

iii) How many grams of carbon dioxide are released per home over the course of one year?

c) Approximately 24, 000 lb of carbon dioxide is emitted per year just by driving alone. Which process (driving or heating the home with propane) emits more carbon dioxide?

Answer 1

volume of propane used by a home is given = 850 gal convert
this volume to mass of propane,using density given

density of propane= 4.2 lb/gal
volume of propane= 850 gal
mass of propane = volume xdensity = 850 gal*4.2 lb/gal
= 3570 lb
now covert this mass to grams
1lb= 453.59 g

mass of propane = 3570 *453.59 g= 1.62 x10^6 g

this much grams of propane is burned
convert mass in to moles using molar mass of propane

Number of moles of propane = mass/molar mass =1.62 x10^6 g/44.1 g/mol
= 3.67 x10^4 moles
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b)Propane reacts with oxygen to produce carbon dioxide and water.

C3H8(g) +5O2(g) ----> 3CO2(g) + 4H2O(l)
is the balanced combustion reaction

2)from balanced equation it is clear that 1 mole propane releases 3 moles
CO2 gas

from above; 1 year ,3.67 x10^4 moles of propane is consumed

So moles of CO2 produced =3.67 x10^4 * 3 moles = 11.01x10^4
moles of CO2 is released
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3) grams of CO2 produced = moles of CO2 *molar mass of CO2

=11.01x10^4*44.01 g/mol= 484.55 x10^4 g CO2 will be produced

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c) convert above mass of CO2 in to Lb
mass of co2 produced = 484.55 x10^4 /453.59 = 1.068 x10^4 lb
= 10,680 lb

CO2 emitted by driving is more than that from burning propane
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Thank you.