2.5 grams of a substance is .021 moles of the substance

1/.021 = 47.6.......

2.5 x 47.6...... = 1 mole?

1 mole = 119 .... gram ?

yes?

Are you trying to find the substance?

any time you multiply/divide, include units along with the numbers. that way you'll always know what your units are and it'll help you make sense of what you're doing.

why 1/0.021?

moles = mass / RMM so just rearrange for RMM

RMM = mass / moles ( 2.5 / 0.021 = RMM)

= 119 g mol-1

I guess he thought the conversion rate was 1g/1mol
But if you were looking for the substance, then use the numbers above and you'll get Tin, Sn (118.9~)

No I have a mole amount and grams but I do not have molecular formula of the substance and therefore cannot easily plug in elemental masses to find overall molecular weight.

All I know is that the sample of the substance weighs 2.5 grams and that 2.5 grams of the substance is equivalent to .021 moles of the substance . I need to figure out what 1 mole weighs. Basic grams/mole molecular weight. So how would I do this algebraically? 1 mole is 47.6... X more than the .021 which is 2.5 gram so I just multiply grams by 47 and that is 1 mole?

yes, that is correct