Question

A gas used to extinguish fires is composed of 75 % CO2 and 25 % N2. It is stored in a 5 m3 tank at 300 kPa and 25 °C. What is the partial pressure of the CO2 in the tank in psia?

Answer 1

Answer : The partial pressure of the
`CO_2` in the tank in psia is, 32.6 psia.

Explanation :

As we are given 75 %
`CO_2` and 25 %
`N_2` in terms of volume.

First we have to calculate the moles of
`CO_2` and
`N_2`.

`\text{Moles of }CO_2=\frac{\text{Volume of }CO_2}{\text{Volume at STP}}=(75)/(22.4)=3.35mole`

`\text{Moles of }N_2=\frac{\text{Volume of }N_2}{\text{Volume at STP}}=(25)/(22.4)=1.12mole`

Now we have to calculate the mole fraction of
`CO_2`.

`\text{Mole fraction of }CO_2=\frac{\text{Moles of }CO_2}{\text{Moles of }CO_2+\text{Moles of }N_2}`

`\text{Mole fraction of }CO_2=(3.35)/(3.35+1.12)=0.75`

Now we have to calculate the partial pressure of the
`CO_2` gas.

`\text{Partial pressure of }CO_2=\text{Mole fraction of }CO_2* \text{Total pressure of gas}`

`\text{Partial pressure of }CO_2=0.75mole* 300Kpa=225Kpa=225Kpa* \frac{0.145\text{ psia}}{1Kpa}=32.625\text{ psia}`

conversion used : (1 Kpa = 0.145 psia)

Therefore, the partial pressure of the
`CO_2` in the tank in psia is, 32.6 psia.