A -> 3C

The molar mass of A is 10.0g/mol

If 2.0 grams of A reacts, how many moles of C will be produced?

A -------------------> 3C
m.mass= 10.0g/mol
mass = 2.0 g
moles = 2.0 g/10.0 g/mol
=0.2 mol

moles of c = 3 x 0.2 = 0.6 mol

Did I do this correctly?

yes. or you can write it as

2.0 g A x (1 mole A/10.0 g A) x (3 moles C/1 mole A) = 0.6 mole C. Note that doing it this way, g A cancels with g A to give moles A, then moles A cancel with moles A and the only unit left is moles C which is what you wanted. The factors are arranged so that you cancel those units you don't want to keep and keep the unit required for the problem.

Ohhh.. OK. I understand. Thank you soo much for all your help today :)

Yes, you did the calculation correctly!

To find the number of moles of C produced when 2.0 grams of A reacts, you first need to find the number of moles of A. This can be done by dividing the mass of A (2.0 grams) by its molar mass (10.0 g/mol).

So, moles of A = 2.0 g / 10.0 g/mol = 0.2 mol

Now, since the balanced chemical equation shows that for every mole of A, 3 moles of C are produced, you can multiply the moles of A by the mole ratio to find the moles of C.

Moles of C = 3 x 0.2 mol = 0.6 mol

Therefore, when 2.0 grams of A reacts, 0.6 moles of C will be produced.