Question

What is the mass of 1.532 moles of a compound with a molar mass of 44 g/mol?

Answer 1

`"67.41 g"`

Explanation:

The idea here is that the molar mass of a compound can be used as a conversion factor between grams and moles.

As you know, the molar mass tells you the mass of one mole of a given compound. In your case, the compound is said to have a molar mass equal to `"44 g mol"^(-1)`.

This means that if you were to measure out exactly one mole of this compound, its mass would be equal to `"44 g"`.

Now, your sample contains `1.532` moles of this unknown compound. To use the molar mass a conversion factor, place the unit that you have on the bottom of the fraction and the unit that you need on the top of the fraction

You will thus have

`color(blue)(|bar(ul(color(white)(a/a)"have moles" * "44 grams"/"1 mole" = "get grams"color(white)(a/a)|)))`

or, when you have grams and need moles

`color(blue)(|bar(ul(color(white)(a/a)"have grams" * "1 mole"/"44 grams" = "get moles"color(white)(a/a)|)))`

Plug in your values to find

`1.532 color(red)(cancel(color(black)("moles"))) * "44 g"/(1color(red)(cancel(color(black)("mole")))) = color(green)(|bar(ul(color(white)(a/a)color(black)("67.41 g")color(white)(a/a)|)))`

I'll leave the answer rounded to four sig figs because you can say that the molar mass of the compound is a constant, which implies that it has an "infinite" number of sig figs.