Question

The thermochemical equation for the combustion of rubbing alcohol is 2C3H7OH (l) + 9O2 → 6CO2 +8H2O(l) ΔH = -474.8 kJ Calculate the amount of heat released when 25.0 g of rubbing alcohol is combusted.

Answer 1

Amount of heat released when 25.0 g of
`C_(3)H_(7)OH` (rubbing alcohol) is combusted equal to 98.7 kJ

Step-by-step explanation:

According to balanced equation (as given in problem), combustion of 2 moles of rubbing alcohol release 474.28 kJ of heat.

Molar mass of
`C_(3)H_(7)OH` (rubbing alcohol) = 60.095 g/mol

We know, number of moles of a compound is the ratio of mass to molar mass of that compound.

So, 2 moles of
`C_(3)H_(7)OH` (rubbing alcohol) =
`(2* 60.095)g`
`C_(3)H_(7)OH` (rubbing alcohol) = 120.19 g of
`C_(3)H_(7)OH` (rubbing alcohol)

So, combustion of 120.19 g of rubbing alcohol release 474.28 kJ of heat.

Hence amount of heat released when 25.0 g of
`C_(3)H_(7)OH` (rubbing alcohol) is combusted =
`(474.28* (25.0)/(120.19))kJ=98.7kJ`