How do you determine the number of moles in these?

Question

You have to figure out the number of moles in 25 g of NaCl.

I'm using the equation

n=m/mw

where:

n=moles

m=mass

mw=molar weight.

so i did

n=(25 g)/(58.44 mol)

n=.43 g/mol

is this the correct equation to use? and if it is do you do anything to that answer in order to get the actual answer, or do you just leave it as it is?

Answer 1

Moles = Mass / Mol.mass.

The answer will be in moles not g/mol.

Na = 23, Cl = 35.44;

NaCl = 58.44g/mol.

25g / 58.44g/mol. = 0.428 mole.

Answer 2

Yes, this is a correct equation. You leave it just like that, although you have problems with your units.

mass is in grams and molar weight is in gram/moles, therefore, moles will be grams/(grams/mole) would be moles.

Your number of sig figs is correct.

Answer 3

That's the correct equation to use and also the correct answer (although the units should only be moles I think).