what is an easy way to remember how to find mass, number or moles, number of particles,?

Question

i have a test tomorrow on how to find mass, number of particles molar mass, number of moles etc. I am having so much trouble in trying to remember all the formulas :-( Please help!!

Answer 1

It is not really a matter of knowing formulas, as long as you know avagadro's nember (6.022x10^23) you should be fine. All you need to know how to get the answer you want. so if you are given grams and need atoms then you write it kind of like this.

g * (mol/g)- in this step grams go away because they are on the top and bottom

mol * (6.022x10^23atoms/mol) - in this step moles go away becasue they are on top and bottom.

Don't try to remember formulas, just manuver your units until everything is gone except for what you need. Do remeber 6.022x10^23 though.

Answer 2

The main thing you need to know is that when you have mass and problems deal with moles, number of particles, molar conc. you MUST convert by dividing the weight of the substance by its g-atomic weight (if an element) or its mole wt (if a compound).