Question #e811d

1 Answer
Mar 3, 2017

"0.43 moles N"_20.43 moles N2

Explanation:

Start by writing a balanced chemical equation that describes this synthesis reaction

"N"_ (2(g)) + color(blue)(3)"H"_ (2(g)) -> color(red)(2)"NH"_ (3(g))N2(g)+3H2(g)2NH3(g)

The thing to remember about balanced chemical equations is that the coefficients added in front of a chemical species represent the number of moles of said chemical species needed in order for the reaction to take place.

In this case, you need 11 mole of hydrogen gas for every color(blue)(3)3 moles of hydrogen gas in order to produce color(red)(2)2 moles of ammonia.

Now, these mole ratios are true regardless of how many moles of a particular chemical species you have. In other words, you will have

"number of moles of N"_2/"number of moles of NH"_3 = 1/color(red)(2)number of moles of N2number of moles of NH3=12

Similarly, you will also have

"number of moles of H"_2/"number of moles of N"_2 = color(blue)(3)/1number of moles of H2number of moles of N2=31

and

"number of moles of H"_2/"number of moles of NH"_3 = color(blue)(3)/color(red)(2)number of moles of H2number of moles of NH3=32

In your case, you know that 0.850.85 moles of ammonia were produced by the reaction. Since the 1:color(red)(2)1:2 mole ratio that exists between nitrogen gas and ammonia tells you that

"no. of moles of N"_2 = 1/color(red)(2) * "no. of moles of NH"_3no. of moles of N2=12no. of moles of NH3

you can say that the reaction consumed

"no. of moles of N"_2 = 1/color(red)(2) * "0.85 moles" = color(darkgreen)(ul(color(black)("0.43 moles N"_2)))

The answer must be rounded to two sig figs, the number of sig figs you have for the number of moles of ammonia produced by the reaction.