mole help for yr 11?

[schnappy]

Edit: Wow this post was wrong, I won't post at midnight so often.

[Mao]

All i'll say is,
when a question asks for amount of something, your answer will be in mol
What is a mol?  A mol is the number of atoms contained 12.0 grams of Carbon-12. This number is 6.02 x 10^23 - a very large number.
The molar mass of something, for example, hydrogen is the mass of 1 mol of that substance. I.e, 6.02 x 10^23 (or 1 mole) of hydrogen atoms will weight approximately 1 gram (as given in your periodic table.)

With this knowledge, you can work out the mass, or amount in mol of anything, given you have at least 1 or the other. If you can make a logical link between the formulas and how they work, you are well on your way to acing stoich.

For example, the formula for working out mols is:

Why?
See how it works:
1 mol of hydrogen weighs 1 gram,
according to the periodic table the molar mass of hydrogen is 1 gram per mol, that is, if we have 1 mol of hydrogen atoms and weigh it, it will = roughly a gram.


So, if we have 2 grams of hydrogen, how many mol of hydrogen will we have? using , where m= 2 and = 1, we will have 2/1 = 2 mols of hydrogen.

A much easier way to think about it: Mr is given by g/mol, thus

(similar with concentration in mol/L, thus , molar volume (STP or SLC) is given by L/mol, thus , etc)

[Kaille]

sorry, i've got another question.

What is the total mass of ethane?

Is this the same question or do you mean Molar Mass (You probs don't know what this is yet...)

like the mass in grams. i figured it out and i get 3.0 grams. i divided the number of ethane molecules by avogadro's number.

thanks for the help guys

[Dream-Storm]

Well, that has helped me a fair bit. I'm struggling to recognise the formulas needed to work out the molar mass and stuff. My brain erally isn't in it at the moment...