Answer:
1.33 moles per second
Explanation:
From the balanced equation of reaction, 3 moles of H2(g) need to disappear/be consumed before 2 moles of NH3(g) can be formed/appear.
According to reaction law, the rate of disappearance of reactants is equal to the rate of appearance of products.
Now, only 2 moles per seconds of H2 has disappeared initially;
3 moles H2 is needed for 2 moles NH3
2 moles H2 will give; 2 x 2/3 = 4/3 or 1.33 moles
Hence, if the initial rate of disappearance of H2 is 2.0 moles per second, the initial rate of appearance of NH3 would be 1.33 moles per second.