If 150 g dimethylhydrazine reacts with excess dinitrogen tetroxide and the product gases are collected at 127oc in an evacuated 250-l tank, what is the partial pressure of nitrogen gas produced and what is the total pressure in the tank assuming the reaction has 100% yield?

Answer : The the partial pressure of the nitrogen gas is 0.981 atm.

The total pressure in the tank is 2.94 atm.

Explanation :

The balanced chemical reaction will be:

First we have to calculate the moles of dimethylhydrazine.

Mass of dimethylhydrazine = 150 g

Molar mass of dimethylhydrazine =60.104 g/mole

Now we have to calculate the moles of gas.

From the balanced chemical reaction we conclude that,

As, 1 mole of react to give 3 moles of gas

So, 2.49 mole of react to give moles of gas

Now we have to calculate the partial pressure of nitrogen gas.

Using ideal gas equation :

where,

P = Pressure of gas = ?

V = Volume of gas = 250 L

n = number of moles   gas = 7.47 mole

R = Gas constant =

T = Temperature of gas =

Putting values in above equation, we get:

Thus, the partial pressure of the nitrogen gas is 0.981 atm.

Now we have to calculate the total pressure in the tank.

Formula used :

where,

= total pressure = ?

= partial pressure of nitrogen gas = 0.981 atm

= moles of nitrogen gas = 3 mole  (from the reaction)

= total moles of gas = (3+4+2) = 9 mole  (from the reaction)

Now put all the given values in the above formula, we get:

Thus, the total pressure in the tank is 2.94 atm.

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