Question

What is the mass of 0.5 moles of `"CO"_2` ?

Answer 1

`22` grams.

Explanation:

We use the following formula

`n("moles") = (m("mass"))/(M("molar mass"))`

Rearranging this equation, we find that

`m = n * M`

We are given the moles `(0.5)`, so we need to find the molar mass. I'm assuming you are given a table of molar values of elements such as carbon is `"12 g/mol"`..

So to find moles, we add all the molar values together

`M("CO"_2) = M("C") + 2*M("O")`

`M("CO"_2) = (12 + 2*16) \ "g/mol"`

`M("CO"_2) = 44 \ "g/mol"`

Therefore, we can then use the above-rearranged equation to find `m`:

`m = "0.5 moles" * "44 g/mol"`

`m = "22 g"`

Answer 2

`22` grams

Explanation:

To find the mass of a certain number of moles of a substance, we multiply the number of moles of the substance by its molar mass.

Carbon dioxide `(CO_2)` has a molar mass of `44.01 \ "g/mol"`. Here, there are `0.5 \ "mol"` of the molecule. So, the mass of this sample is:

`m=(44.01 \ "g")/(color(red)cancelcolor(black)"mol")*0.5color(red)cancelcolor(black)"mol"`

`~~22 \ "g"`