N2(g) + 3H2(g) 2NH3(g) at STP
How many litres of ammonia gas is produced using 5 litres of H2?
N2 + 3H2 ---> 2NH3
- the ratio between H2 and NH3 is 3 : 2
- it's given 5 litres of H2, so the volume of NH3 formed is 5/3*2 = 10/3 = 3.33 (L)
Sig FIG ANSWER 3 L
How many moles of N2 are needed?
- 5 litres of H2 converts to 0.22 moles of H2
- the ratio between N2 and H2 is 1 : 3, so the moles of N2 needed is 0.074 mol
SIG FIG ANSWER 0.1 MOL
The answer for 3.33 looks ok but you're allowed 1 s.f. (from 5L) so wouldn't you round 0.074 to 0.07 and not 0.1 although both 0.07 and 0.1 have 1 s.f.
Your math and conclusions are correct, but suggest keeping in mind the numbers actually refer to 'molar volumes' of gas. Such could pose some confusion when working with gas volumes in practical lab settings. That is,
one should specify temperature and pressure conditions to account for departures from STP conditions. Yes, ratios will be consistent with what your calculation shows, but actual volumes in a lab setting may not be what's expected from theoretical calculations. :-)
so for 0.074 mol is 0.07 mol
yes,You are allowed 1 s.f.because of the 5 L and there is 1 s.f. in 0.07. The 0 is a decimal placer and not a significant digit.
To answer the first question, we can start by looking at the balanced chemical equation:
N2(g) + 3H2(g) → 2NH3(g)
From the equation, we can see that the ratio between H2 and NH3 is 3:2. This means that for every 3 moles of H2, 2 moles of NH3 are produced.
Given that 5 litres of H2 are used, we need to find the amount of NH3 produced. We can use the ratio to determine this:
(5 L H2) * (2 mol NH3 / 3 mol H2) = 3.33 L NH3
Therefore, 5 litres of H2 will produce approximately 3.33 litres of NH3.
To determine the answer in the correct significant figures, round the answer to 3 litres of NH3.
For the second question, we need to find the amount of N2 needed. We know that the ratio between N2 and H2 is 1:3, so for every 1 mole of N2, 3 moles of H2 are required.
Given that we have 5 litres of H2, we can calculate the number of moles of H2:
(5 L H2) * (1 mol H2 / 22.4 L H2) = 0.22 mol H2
Since the ratio is 1:3, we can determine the amount of N2 required by dividing the moles of H2 by 3:
0.22 mol H2 * (1 mol N2 / 3 mol H2) = 0.074 mol N2
Therefore, approximately 0.1 moles of N2 are needed.
To express this answer with the correct significant figures, round it to 0.1 moles of N2.