ATAR Notes: Forum

HSC Stuff => HSC Science Stuff => HSC Subjects + Help => HSC Chemistry => Topic started by: sangarp on November 03, 2019, 01:33:58 pm

Title: CHEMISTRY ENTHALPY HSC MCQ
Post by: sangarp on November 03, 2019, 01:33:58 pm

Hey need some help on this asap
How do you do this?

Title: Re: CHEMISTRY ENTHALPY HSC MCQ
Post by: r1ckworthy on November 03, 2019, 01:59:24 pm

Quote from: sangarp on November 03, 2019, 01:33:58 pm

Hey need some help on this asap
How do you do this?

Hey! There might be a quicker way, but from what I can see, I would divide each value on the table to convert it from kJ/ g to kJ/mol. The value that matches 3218 is the correct fuel.

Title: Re: CHEMISTRY ENTHALPY HSC MCQ
Post by: sangarp on November 03, 2019, 02:57:03 pm

hey
I actually did that
But I don't seem to get any of the values that have been given

Title: Re: CHEMISTRY ENTHALPY HSC MCQ
Post by: r1ckworthy on November 03, 2019, 03:28:23 pm

Sorry! I made a silly mistake- you have to multiply all combustion values with it's molar mass in order to convert it to kJ/mol.

Molar mass comes in the form of g / mol. So, if we multiple the heat of combustion (kJ /g) of each fuel by it's molar mass (g/ mol), we convert the value to kJ /mol. Attached is an example of how I did it for one of the fuels.

(https://i.ibb.co/4P4sg8g/IMG-1344.jpg)

Again, sorry for the silly mistake! Another lesson of why you shouldn't do things in your head ;D