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# Moles (not the ones that live underground i'm talking chemistry here)

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1. Hey!

So i can comprehend that moles = volume (divided by 1000 to get from cm cubed to dm cubed) x concentration.

BUT

Does moles also = weight/Mr??? Or is this molar mass? I'm so confused. Please can somebody please explain, thank you!
Hey!

So i can comprehend that moles = volume (divided by 1000 to get from cm cubed to dm cubed) x concentration.

BUT

Does moles also = weight/Mr??? Or is this molar mass? I'm so confused. Please can somebody please explain, thank you!
Moles of a substance = mass/molar mass.
When the substance is dissolved in a liquid, moles = volume of the liquid (dm cubed) x concentration (mol dm cubed)

Let me know if you still don't understand
3. (Original post by ozmo19)
Moles of a substance = mass/molar mass.
What is molar mass?? (thank you btw)
4. The molar mass of a substance is the mass of one mole (so 6.022 x 10^23 particles) of a substance - it's the same as the ar/mr.

So if you wanted the molar mass of Na, it's 23g as it's mass number is 23.
What is molar mass?? (thank you btw)
Molar mass is properly known as the mass of one mole of a substance. The units are g/mol
But, don't get caught up in that definition.
In this case, its basically the RFM of the compound. So, you add the RAM of each atom of each element in the molecule.
e.g.
Calculate the moles in 2.0g of Magnesium Bromide - MgBr2
moles= mass/molar mass
moles= 2.0 / (24 + 80 + 80)
...

Hope this helped.
6. (Original post by ozmo19)
Molar mass is properly known as the mass of one mole of a substance. The units are g/mol
But, don't get caught up in that definition.
In this case, its basically the RFM of the compound. So, you add the RAM of each atom of each element in the molecule.
e.g.
Calculate the moles in 2.0g of Magnesium Bromide - MgBr2
moles= mass/molar mass
moles= 2.0 / (24 + 80 + 80)
...

Hope this helped.
(Original post by hoafanuk)
The molar mass of a substance is the mass of one mole (so 6.022 x 10^23 particles) of substance - it's the same as the ar/mr.

So if you wanted the molar mass of Na, it's 23g as it's mass number is 23.

Ohhhhh okay! So say it wants you to find the number of moles of 50g of sodium chloride, and its MR is 58.5 you would divide 50 by 58.5 and the answer would be 0.85 g/mol?
Ohhhhh okay! So say it wants you to find the number of moles of 50g of sodium chloride, and its MR is 58.5 you would divide 50 by 58.5 and the answer would be 0.85 g/mol?
You used the units for molar mass.
Since you used
moles= mass (g) / molar mass (g/mol),
units for moles are just mol.
You did the division right and the final answer is 0.855 mol.
8. (Original post by ozmo19)
You used the units for molar mass.
Since you used
moles= mass (g) / molar mass (g/mol),
units for moles are just mol.
You did the division right and the final answer is 0.855 mol.
Oh okay! Thank you so much!

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