Question

A gaseous mixture containing 0.35 g of N2 and 5600 ml of O2 at STP is kept in 5 litres of flask at 300K. The total pressure of the gaseous mixture is:
A. 1.293 atm
B. 1.2315 atm
C. 12.315 atm
D. 0.616 atm

Answer 1

Hint: In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas if it alone occupied the entire volume of the original mixture at the same temperature, i.e. If a mixture contain 3 gases such as A, B, and C then the total pressure of that mixture will be the sum of their partial pressure of each gases
$$\Rightarrow P_{Total}=p_A+p_B+p_C$$

Complete step by step answer:
In the question we have given that 0.35 g N2 and 5600 ml O2, hence the total pressure of the container will be,
$$\Rightarrow P_{Total}=p_{N_2}+p_{O_2}$$
$$p_{N_2}$$= Partial pressure of N2
$$p_{O_2}$$= Partial pressure of O2
Here we have partial pressure of nitrogen is equal to,
$$\Rightarrow p_{N_2}={\displaystyle \frac{n_{N_2}\times R\times T}{V}}$$
$$\Rightarrow n_{N_2}=$$No of moles of N2 = 0.35÷28 (molecular mass of nitrogen is 28 g)= 0.0125 mole
$$\Rightarrow R=$$Ideal gas constant= 0.0821 atm L/mol K
$$\Rightarrow T=$$Temperature= 300 K
$$\Rightarrow V=$$Total volume= 5 Litre
Substitute these values in the equation, then we get
$$\Rightarrow p_{N_2}={\displaystyle \frac{0.0125\times 0.0821\times 300}{5}}=0.061atm$$
Like this we have to find the partial pressure of 5600 ml of O2 at STP. 1 mole oxygen contains 22400 ml of oxygen, here we have 5600 ml. So 5600 ml of oxygen contain,
$$\Rightarrow {\displaystyle \frac{5600}{22400}}mole=0.25mole$$
 Hence we get the no of mole of oxygen as 0.25 moles. Then we have partial pressure of oxygen is equal to,
$$\Rightarrow p_{O_2}={\displaystyle \frac{n_{O_2}\times R\times T}{V}}$$
$$\Rightarrow n_{O_2}$$= 0.25 mole
Substitute these values in the equations. Then we get,
$$\Rightarrow p_{O_2}={\displaystyle \frac{0.25\times 0.0821\times 300}{5}}=1.231atm$$
Hence the total pressure of the mixture is equal to
$$\Rightarrow P_{Total}=p_{N_2}+p_{O_2}$$
$$\Rightarrow P_{total}=0.061+1.231=1.293atm$$

The total pressure is 1.293 atm .Hence, the correct answer is option A.

Note:
Please note that the mixture should contain non-reactive gas. They should not react with each other. If once they react the individual gases give rise to a new product. For a mixture of nitrogen and hydrogen the partial pressure concept can not be applied. Because they will react to each other and form ammonia gas.