# Calculations

The fHo of Ethanol (CH3CH2OH) (l)), Water (H2O (l)) and carbon Dioxide (CO2(g)) at 298K are respectively; -277.1 kJ mol-1, -285.8 kJ mol-1 and –393.5 kJ mol-1. Given that the latent heat of fusion of water is 6.02 kJ mol-1 and the average heat capacity of water is 75.3 J K-1 mol-1 how much ice (in grams) would be needed to put in a measure of whisky (25ml, 40% ethanol by volume) such that all the enthalpy of combustion of the ethanol is taken up raising the temperature of the ice to body temperature (35C). Density of ethanol = 0.789 g cm-3 (16 marks)

Your first stage in answering this question is calculating the enthalpy of combustion for ethanol using the enthalpy of formation data.
science2chemistrytutor
05 April 2012
I need help with the same type of question. What do you do after this?
emmalouram
12 April 2012
For the question above: Next you need to calculate enthalpy of combustion for the amount of ethanol in a measure of whisky.
science2chemistrytutor
13 April 2012
Ok, I've done this. Im confused at what to do next
emmalouram
13 April 2012
Once you have calculated the enthalpy of combustion of the ethanol in a measure of whisky. The next steps involve calculating the mass of ice you would need so when the ethanol is burnt in complete combustion the ice melts and the temperature of water raises to 35C
science2chemistrytutor
19 April 2012
If the value of Enthalpy of combustion for 10 ml ethanol has equal to the total energy required to melt the ice and heat the ice to 35C. You can rewrite this as an equation like so....................... Enthalpy of combustion for 10 ml ethanol. = (Enthalpy of fusion (melting) of x mol of water) + (heat energy to raise x mol of water by 35C). The only problem being you don't know x number of moles need.
science2chemistrytutor
19 April 2012
To calculate the x mol of ice needed you can work out the energy require to melt and heat 1 mole of ice to 35C (= (latent heat of fusion 1 mol of water) + (heat energy required to heat 1 mol water to 35C). To calculate the actual number of mole of ice require take enthalpy of combustion of ethanol in a measure of whisky / energy require to melt and heat 1 mole of ice to 35C. Once you have the number of mole you can then calculate the mass.
science2chemistrytutor
19 April 2012