# How do I convert kj/g to kj/mol (1 Viewer)

#### Hivaclibtibcharkwa

##### 𝗕𝗶𝗼𝗹𝗼𝗴𝘆 𝗧𝘂𝘁𝗼𝗿

I’m trying to make the grams into moles by diving by molar mass. But since grams are in the denominator I’m having a hard time divi The grams by molar mass

#### XXXPUMPERXXX

##### Member
In this question either way you will have to just test for all values. I think you should just multiply the molar mass by the kj/g that would still give the answer. Also if you just wanna convert kj/g to kj/mol just multiply it by the molar mass.

Last edited:

Moderator

#### Eagle Mum

##### Well-Known Member
Methanol (MW 32): 1 mol = 32 g
Ethanol (MW 46): 1 mol = 46 g
Propanol (MW 60): 1 mol = 60 g
Octane (114): 1 mol = 114 g

2016 kJ / 1 mol
Substitute mass in grams for 1 mole:

Methanol: 2016 kJ / 32 g = 63 kJ / g (not 22.7 kJ /g)
Ethanol: 2016 kJ / 46 g = 43.8 kJ / g (not 29.6 kJ /g)
Propanol: 2016 kJ / 60 g = 33.6 kJ / g Correct option
Octane: 2016 kJ / 114 g = 17.7 kJ / g (not 47.8 kJ /g)

#### someth1ng

##### Retired Nov '14
In your picture, you write it weird. It makes more sense to write it as:
(kJ/g) x (g/mol) = (kJ.g)/(g.mol) = kJ/mol

You work with units in the same way you work with numbers (in algebra).

#### CM_Tutor

##### Moderator
Moderator
In your picture, you write it weird. It makes more sense to write it as:
(kJ/g) x (g/mol) = (kJ.g)/(g.mol) = kJ/mol

You work with units in the same way you work with numbers (in algebra).
Yes, but in unit terms, it works equally well as

$\bg_white \text{Unit on RHS}\ = \cfrac{\text{kJ mol}^{-1}}{\text{g mol}^{-1}} = \cfrac{\text{kJ}}{\text{g}} =\ \text{kJ g}^{-1}\ =\ \text{unit on LHS}$

and the question I was addressing was converting from kJ mol-1 to kJ g-1.

Of course, the formulae

$\bg_white \Delta H\ \left(\text{in kJ g}^{-1}\right) = \cfrac{\Delta H\ \left(\text{in kJ mol}^{-1}\right)}{M\ \left(\text{in g mol}^{-1}\right)}$

and

$\bg_white \Delta H\ \left(\text{in kJ mol}^{-1}\right) = \Delta H\ \left(\text{in kJ g}^{-1}\right)\ \times\ M\ \left(\text{in g mol}^{-1}\right)$

are the simple rearrangements of each other, and actually just one case of a more general process for converting between mole and mass based units - expressing concentration in mol L-1 or g L-1 being another example.