Question

Predict the change in enthalpy due to combustion of 10.0g of propane used in a camp stove

Answer 1

@aaronq @zepdrix

Answer 2

Use Hess's Law

Answer 3

cannt i use caloirmetry ?

Answer 4

we didnt get to hesses law yet so my teacher will be pissed

Answer 5

you can use calorimetry if you know other data; like the change in temperature of the calorimeter system

Answer 6

this is an excample on my book and it says the molar entlapy is -2043.9kj i dont get where they got the number from

Answer 7

Okay, so you can use that value?

\(\Delta H_{rxn}=H^0_{combustion}*n\)

so convert the 10 g to moles and multiply by the molar enthalpy

Answer 8

but how do i know the molar entlahy

Answer 9

its not given in the question

Answer 10

you often have to look these up; these are standard values in any textbook, on a test or exam they would be given to you.

Answer 11

unless they give you other information to work it out from

Answer 12

like in my data table its is given for propnae -103.8

Answer 13

hm what are the units on both values?

Answer 14

but that way off of what they put in for the molar entaloy

Answer 15

u mean answer ?

Answer 16

no for the standard molar enthalpies you're giving; what are the units, it's possible one is in kJ/mol and the other in kJ/g

Answer 17

kj/mol

Answer 18

for propane it says -103 kj/mol

Answer 19

That's the enthalpy of formation; the other is the enthalpy of combustion.

To use the enthalpy of formation you need to use Hess's Law

Answer 20

ok , can u help me with another one