I'm sorry if my question seemed like I was taking advantage of this thread.
I was unsure how to calculate molar mass, moles and ect and what formula I needed to use.
I am still quite confused about molar mass and moles calculations in general.
Could I have help in understanding when to use what formula and where to use it?
That's not a problem
Okay, so let's do a brief refresher of moles, molar mass and mass, and how to calculate each from the other.
A
mole is a collection of atoms (in fact, it is an exact number of atoms, Avagadro's number. This isn't important in the HSC, but knowing this makes understanding the concepts a lot easier). 2 moles is two times Avagadro's number of atoms, 1/2 a mole is 50% Avagadro's number etc. As you will imagine, each element's atom will have a different
mass. So, if a single atom of Nitrogen was heavier than a single atom of Helium, you would expect a mole of Nitrogen to weigh more than a single mole of Helium (despite them having the same number of atoms!). The
molar mass of a substance is the mass of one mole of the element.
So, let's put this all together into some calculations. The formula for relating all of this is
So, if we had 3g of Carbon, which has a molar mass of approximately 12g, then we have 1/4 moles of Carbon!
Easy.
Now, there's some more complicated maths that I think your assignment required you to do. Say you had a reaction between two substances. You can balance the equation easily, by adding numbers out the front of each reactant and product to make sure the same number of elements/atoms are on each side. A 2 signifies 2 moles, a 1 signifies 1 mole etc. Now, say you had a reaction that looks something like this:
We know that for any two moles of A, we need 1 mole of B to react, which will produce 1 mole of C. Therefore, if we know we have 2g of A, we can use the above formula to figure out how many moles that is (using the molar mass). We then know we need HALF as many moles of B, and can figure out the relevant mass of B (using it's molar mass). This is stuff that's really important to the HSC syllabus; I'm not sure what level you're at but hopefully this sounds familiar.
That's the basics of the whole thing. I could go into much more depth, but that really is a bulk of the skills in this course. If what I've written above doesn't make sense, or you're having trouble with anything, please feel free to post specific questions because at the moment it's hard to gauge where you're having problems. If none of this is making any sense, I would talk to your teacher about having a few lessons with them. It's a big topic area, and it's important you understand what's going on.
Hope that this helped, at least a little.
Jake