alleryStart learning →For N2 + 3H2 forming 2NH3 with Kc = 6.00 x 10^-2, [N2] = 4.26 M and [H2] = 2.09 M. What is [NH3]?
A0.53 M
B2.33 M
C1.53 M
D0.77 M
Answer & Solution
Correct answer: C. 1.53 M
1. Write the expression: Kc = [NH3] squared divided by ([N2] x [H2] cubed).
2. Cube the hydrogen term: 2.09 x 2.09 x 2.09 = 9.13.
3. Multiply by the nitrogen term: 4.26 x 9.13 = 38.9.
4. Rearrange: [NH3] squared = Kc x 38.9 = 6.00 x 10^-2 x 38.9 = 2.33.
5. Take the square root: the root of 2.33 is 1.53.
6. So the ammonia concentration is 1.53 mol per litre.
7. Quoting 2.33 M is the trap of stopping before the square root is taken.
8. Using the hydrogen term unsquared, or uncubed, gives the other two offered values.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 13 "Fundamental Equilibrium Concepts", section 13.4 Equilibrium Calculations_
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