Molar heat question (1 Viewer)

[chingyloke]

The molar heat of combustion of ethanol is 1360kJ/mol. What will be the final temperature if 250g of water at 20 degrees celsius is heated by the combustion of 2.0g of ethanol if there is a 30% heat loss to the surroundings?

I did it and got some whacked answer. Can anybody help with a worked solution? would be greatly appreciated.

 

[Trebla]

The molar heat of combustion of ethanol is 1360kJ/mol. What will be the final temperature if 250g of water at 20 degrees celsius is heated by the combustion of 2.0g of ethanol if there is a 30% heat loss to the surroundings?

I did it and got some whacked answer. Can anybody help with a worked solution? would be greatly appreciated.

1 360 000 J of heat is released per mole
Moles of ethanol: 2.0 / (12.01 x 2 + 1.008 x 6 + 16.00) = 0.0434
Therefore heat released by 2.0 grams of ethanol is: 0.0434 x 1 360 000 = 59 043.156 J
But 30% is lost to surroundings, which leaves
0.7 x 59 043.156 = 41 330.20752 J

ΔH = mcΔT
41 330.20752 = 250 x 4.18 x (T₂ - 20)
T₂ = 59.55 degrees Celsius
~ 60 degrees Celsius (to 2 significant figures)