Conquering Chemistry - Heat of Combustion (1 Viewer)

[Casson8]

Hi, I'm currently working through some questions in the Conquering Chemistry textbook but there are no worked answers or steps. Could anybody possibly help me with questions 37-41 out of the Chapter 1 or give me any steps/clues to remember the processes?

Cheers

 

[deswa1]

Can you scan the question or type it? Not all of us have the book...

 

[Casson8]

37) The heat of combustion of ethanol is 1360kJ/mol. What mass of ethanol needs to be burnt to raise the temperature of 350g water through 77°C if 50% of the heat released by the ethanol is lost to the surroundings? (The specific heat capacity of water is 4.2J/g/K.)

 

[nightweaver066]

37) The heat of combustion of ethanol is 1360kJ/mol. What mass of ethanol needs to be burnt to raise the temperature of 350g water through 77°C if 50% of the heat released by the ethanol is lost to the surroundings? (The specific heat capacity of water is 4.2J/g/K.)

First lets calculate the amount of energy required to be transferred.









Now we want to know what mass of ethanol must be combusted to produce double that amount of energy (because 50% of the energy released is lost)

So



Calculating mass of ethanol,



Crap just realised it had heat capacity as 4.2. Just replace 4.18 with it and work through the same steps lol