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# Chem a level energetics calc... Very hard watch

1. Calculate the temperature rise in 250g of water if 0.30g of a fuel (with Mr = 81.2 and ethalpy of combustion= -3350 kjmol-1) is burned

2. (Original post by orange565)
Calculate the temperature rise in 250g of water if 0.30g of a fuel (with Mr = 81.2 and ethalpy of combustion= -3350 kjmol-1) is burned

Convert 0.3g of fuel to moles.
From that work out enthalpy change using the enthalpy of combustion.
Then do
3. (Original post by StayWoke)
Convert 0.3g of fuel to moles.
From that work out enthalpy change using the enthalpy of combustion.
Then do
thanks for the reply but I don't get the 2nd and 3rd steps.. which equation do i use since i don't know the temperature rise...

ive done this so far:

moles = 0.3 g /81.2 = 3.69 x 10-3
4. (Original post by orange565)
thanks for the reply but I don't get the 2nd and 3rd steps.. which equation do i use since i don't know the temperature rise...

ive done this so far:

moles = 0.3 g /81.2 = 3.69 x 10-3
You wrote that the enthalpy of combustion is -3350 kJmol^-1.
Disect that down. What does it mean for the enthalpy of combustion to be -3350kJmol^-1
The units are a big give away.

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