Question

A sample of ammonia (NH3) gas is completely decomposed to nitrogen and hydrogen gases over heated iron wool. If the total pressure is 821 mmHg after the reaction, calculate the partial pressures of N2 and H2. Enter your answers in scientific notation.

Answer 1

Step-by-step explanation:

The given reaction will be as follows.

`NH_(3) \rightarrow 1/2N_(2) + 3/2H_(2)`

As all the ammonia has decomposed into nitrogen and hydrogen. Hence, there will be no ammonia left in the reaction.

Now, using Dalton's law, partial pressure of
`N_(2)` + partial pressure of
`H_(2)` = 821 mm Hg.

As there is 1/2 mole
`N_(2)` for 3/2 moles
`H_(2)`, the partial pressure of
`N_(2)` is 1/3 the partial pressure of the
`H_(2)`.

Let the partial pressure of
`N_(2)` will be x and partial pressure of
`H_(2)` is therefore 3x.

Hence, we will calculate the value of x as follows.

`NH_(3) \rightarrow 1/2N_(2) + 3/2H_(2)`

x + 3x = 821 mm Hg

4x = 821 mm Hg

x = 205.25

Therefore, we can conclude that the partial pressure of
`N_(2)` is 205.25 mm Hg, partial pressure of
`H_(2)` is 615.75 mm Hg.