Help with remembering this........?

Question

ok.... so we are doing conversions with moles and grams in chemistry right, well i know how to do them once the problem is set up, the problem is how do i know what formulas to use with what... because they are so many conversion factors to go with turning moles into grams and molecules to moles and whatnot. its hard to keep track of how to set up your probelm depending on that type of coversion. ... yeah, so how do i remember this?

Answer 1

I have just done this myself, so I know how hard it is. Think of it this way, whatever you start off with will be the beginning of your equation; i.e. you have 350g of carbon, how much is that in moles? So you will start with 350gC x (this will be a fraction:1 mol on the top, and the molar mass on the bottom) equals whatever. Basically, whatever form you start off with (mol, gram, etc) you want to cancel out by leaving it on the bottom, and whatever you want to change it into, put on the top. To change say, 800mol of Carbon into grams, you would have 800molC (molar mass of carbon over 1 mol), and whatever the answer is. So whatever they give you in the beginning problem, that is what you will start off with, and that is what you will need to cancel out. If you are converting to particles, that is the same principle, but you put Avagadro's number in the place of what you need to eventually get. So remember that your final product will be what form is on top of the fraction in the equation, and whatever is on the bottom will be cancelled out (what you start with). If you need more help, email me. Good luck.

Answer 2

Unfortunately, I don't have much to offer to you. It is all dimensional analysis (also known as the factor-label method): g * mol/g = mol or mol * g/mol = g.

The conversion factor you'd use in the molar mass of the compound or substance you're dealing with, which you can find from the atomic masses listed on the periodic table. If you memorize all of the atomic masses...you are my hero.

As for molecules to moles, etc, just remember 6.022x10^23 -- Avagadro's Number. There is 6.022x10^23 of just about ANYTHING in a mole (atoms, molecules, formula units, AMUs, etc). Also - 22.4L/mol at 273K and 1 atmosphere for gases.

Memorization. That is what I have to offer. I'm sorry, but there 'ent much more...just make sure that you're proficient at dimensional analysis and memorize avagadro's number and its uses.

Answer 3

well in terms of setting up using dimensional analysis,
just make sure to keep in mind what the units of what ur converting and the units of what ur converting it to.
also, the unit u are trying to end up with should be on top at the end.
To check if youve done everything right, cancel out the units of everything youve done and they should all cancel out except for the units u need at the end.
hope that helped!