Question

How many molecules (not moles) of nh3 are produced from 5.85×10−4 g of h2?

Answer 1

The number of moles is given by:

`number of moles = (mass of element/compound)/(Molar mass of element/compound)`

Mass of hydrogen,
`H_2` =
`5.85* 10^(-4) g` (given)

Molar mass of hydrogen,
`H_2` =
`2* 1 = 2 g/mol`

Number of moles of hydrogen,
`H_2` =
`(5.85* 10^(-4) g)/(2 g/mol) = 2.92* 10^(-4) mol`

Reaction between
`N_2 and H_2` to form
`NH_3` is:

`N_2 + 3H_2\rightarrow 2NH_3`

From the reaction it is clear that 3 moles of hydrogen gives 2 moles of ammonia and 1 mole of nitrogen gives 2 moles of ammonia .

So,
`2.92* 10^(-4) mol` of
`H_2` gives:

Number of moles of ammonia,
`NH_3` =
`(2)/(3)* 2.92* 10^(-4) = 1.95 * 10^(-4) mol`

Since, in one mole of ammonia,
`NH_3` there are
`6.022* 10^(23)` molecules of ammonia,
`NH_3`.

So, number of molecules in
`1.95 * 10^(-4) mol` of ammonia,
`NH_3` is:

`1.95 * 10^(-4)* 6.022* 10^(23) = 11.74* 10^(19) molecules`

Hence, the number of molecules of ammonia produced by
`5.85* 10^(-4) g` of
`H_2` is
`1.174* 10^(20) molecules`.