[lilmissarah]

I really do not understand moles for my chemistry gcse in 4 weeks time - my science teacher keeps explaining them to me and i still dont get them! Does anyone have any ways to help??

[EierVonSatan]

A mole is the unit for amount. You can have a mole of atoms, molecules, ions, fish, buses...whatever Just like you can have a dozen eggs or cars or planes and so on...

1 mole is 6.02 x 10²³ things.

[Clare~Bear]

I did triple science gcse and never did moles.

If you look on the epriodic table then you'll see the atomic masses of elements. For example Hydrogen is 1, Carbon 12 and Oxygen 16. This means that 1g of Hydrogen is 1 mole and so id 12g of Carbon and 16g of Oxygen.

Like i said, i never did moles before sixth form. So if you let me know what kind of things you have to do that involve them, i can help you. But i don't want to ramble on about things that you don't need to know that might confuse you further.

[lilmissarah]

Okay...well i kinda get that but what about all the stupid calculations and stuff? That is what makes no sense to me!!!

[DavidH20]

As has been said above, its simply a unit of measurement for the number of particles. Moles are used because it would be impractical to talk about the number of atoms that react, as its normally trillions at a time. The mass of one mole of a molecule is equal to the relative molecular mass of the molecule, expressed in grams: for example water, H20, has a molar mass of 18g.

[ThisIsOurDecision]

(Original post by lilmissarah)
Okay...well i kinda get that but what about all the stupid calculations and stuff? That is what makes no sense to me!!!

Like how many moles in 10g of potassium?

For that you need to do moles = mass/Mr.

Or for working out the number of moles in a solution you do (vol/1000)*concentration.

[EierVonSatan]

The main equation is:

moles = mass (g) / RMM

So a question like ''how many moles of carbon are in 48 g?''

moles = 48 g / 12 (the 12 comes from the mass number of carbon in the perioidic table)

48/12 = 4 moles

[lilmissarah]

Okay thanks!
What about empirical formula?
If its any help...I am doing OCR gateway science and some of their questions are really strangely worded!!

[That Bearded Man]

Whenever you react something, you need to think of moles when reacting.

Let's say HCl + NaOH = NaCl + H2O

It turns out that in the above reaction, 38.5g of HCl (1 mole) requires 40g of NaOH (one mole) to react completely. This is why we focus on moles

[marky--mark]

Moles are nearly blind little furry things that live underground and make little mounds in the ground in my back garden. Bastards.

[Jambone2]

MASS = MR x MOLES

CONCENTRATION = MOLES / VOLUME ( IN DM3)

Each mole contains avogadros constant of particles in it. The amount of grams needed to equal avogadro's constant is, helpfully enough, the atomic mass of the element, in grams. Hence 12g of Carbon-12 is one mole.

Empirical formula is the simplest whole number ratio of elements in a compound. For example, molecular formula C6H12Cl2 simplifies down to C3H6Cl.

EDIT: Haha, awh, you're doing GCSE. That's cute. Fml. :')

[AshleighxJayne]

Moles:

N=M/Mr
(N being moles, M being mass and Mr being, obviously, the Mr).

Moles in a solution:
N=CxV
(N being moles, C being concentration and V being volume in dm3.)
For volume in cm3:
N=(CxV)/1000

Draw the little triangles if it helps you, it always helped me.