Question

What is the mass of 3 moles of `"C"_2"H"_2` ?

Answer 1

`"78 g"`

Explanation:

Every mole of `"C"_2"H"_2` (acetylene) has a mass of `"26.04 g"`, i.e. acetylene has a molar mass of `"26.04 g/mol"`.

Thus,

`"26.04 g/mol " * " 3 mol"`

gives you the mass of `3` moles, `"78 g"`

Answer 2

Molar mass of `C_2H_2 => 26g`, that's the mass of 1 mole.

Therefore, mass of 3 moles of `C_2H_2` would be `26 xx 3 = color(red)(78g`

Answer 3

`78 \ "g"`

Explanation:

Acetylene `(C_2H_2)` has a molar mass of `26.04 \ "g/mol"`.

To find out the mass of moles, we have to multiply the number of moles by the molar mass of the substance, i.e. we can form an equation like this:

`"mass"="moles"*"molar mass"`

So, the mass of three moles of acetylene is

`"mass"_(C_2H_2)=3color(red)cancelcolor(black)"mol"*(26.04 \ "g")/(color(red)cancelcolor(black)"mol")=78.12 \ "g"`

Now, we can round off to the nearest whole number to make the answer more reasonable, so it'll be

`78.12 \ "g"~~78 \ "g"`