Question

In the first step of the Ostwald process for the synthesis of nitric acid, ammonia is converted to nitric oxide by the high-temperature reaction
4NH3(g)+5O2(g)→4NO(g)+6H2O(g)

Part A: How is the rate of consumption of O2 related to the rate of consumption of NH3?

Part B: How is the rate of formation of NO related to the rate of consumption of NH3?

Part C: How is the rates of formation of H2O related to the rate of consumption of NH3?

Answer 1

4NH3(g)+5O2(g)---------------------> 4NO(g)+6H2O(g)

rate = - 1/4 *d[NH3] / dt = - 1/5 *d[O2] / dt = + 1/4 *d[NO] / dt = + 1/6 *d[H2O] / dt

'- ' symbol indicates rate of consumption

' + ' symbol indicate rate of formation

Part A: How is the rate of consumption of O2 related to the rate of consumption of NH3?

- 1/4 *d[NH3] / dt = - 1/5 *d[O2] / dt

d[O2] / dt   =5/4 *d[NH3] / dt

rate of consumption of O2 = 5/4 *d[NH3] / dt = 5/4 * rate of consumption of NH3

Part B: How is the rate of formation of NO related to the rate of consumption of NH3?

- 1/4 *d[NH3] / dt = + 1/4 *d[NO] / dt

d[NO] / dt =d[NH3] / dt

rate of formation of NO = - d[NH3] / dt = rate of consumption of NH3

Part C: How is the rates of formation of H2O related to the rate of consumption of NH3?

- 1/4 *d[NH3] / dt = + 1/6 *d[H2O] / dt

d[H2O] / dt = 6/4 *d[NH3] / dt

    d[H2O] / dt     = - 3/2 * d[NH3] / dt

the rates of formation of H2O = - 3/2 * d[NH3] / dt   = 3/2 * rate of consumption of NH3