Question

How many moles of N2H4 are there in 25.8 grams?

Answer 1

`1.648 " mol "N_2H_4`

Explanation:

To convert from grams to moles, we have to multiply the grams by the molar mass.

First, let's find the molar mass of `N_2H4`:
`N_2`: `2((14.007 g)/("mol")) = (28.014 g)/"mol"`

`H_4`: `4((1.008 g)/"mol")) = (4.032 g)/"mol"`

When we add these up, the molar mass of `N_2H_4` is `(28.014 g)/"mol" + (4.032 g)/"mol" = (32.046 g)/"mol"`.

Now we can multiply that by the grams we have:

`52.8cancel( " g " N_2H_4) xx (1 " mol " N_2H_4)/(32.046 cancel(" g " N_2H_4))`

`=> 1.64763153... " mol " N_2H_4`

However, we can only have three significant figures (sig figs) because the original `25.8 " g"` only has `3`, and we are doing multiplication.

So the answer is `1.648 " mol "N_2H_4`

Hope this helps!