Mass of candle 0.72 g before burning. What is the mass of the products of this reaction? Would that be the same thing as weighing the candle again (the mass is 0.27 g after burning)?

1 Answer
May 5, 2017

Refer to explanation

Explanation:

Reweighing the candle before and after burning just shows how much fuel was burnt.
Typical candle wax is an alkane such as hentriacontane, so write a chemical formula for the combustion of this alkane.

#C_31H_64 + 47O_2 -> 31CO_2 + 32H_2O#

Work out the moles for this alkane.

#(0.72g)/(436)#= 0.00165 moles

The mole ratio of the alkane to #CO_2# is 1:31 so multiply the moles of the alkane by 31 to get the number of moles for #CO_2#.

#0.00165*31# =0.0511 moles

Multiply the moles of #CO_2# by #24dm^3# and then by 1000 to get it in #cm^3#.

#1000(0.0511*24) = 1266.4cm^3#

Hence for water, do 0.0511 moles times by its formula mass, 18.

#0.0511*18= 0.92g of water.

(I may have overcomplicated it a bit)