Question

Carbon dioxide (1.100g) was introduced into a 1L flask which contained some pure oxygen gas. The flask was warmed to 373K and the pressure was then found to be 608mmHg. If CO2 and O2 were the only gases present, what was the mass of the oxygen in the flask?

Answer 1

Answer : The mass of oxygen present in the flask is 0.03597 grams.

Explanation :

First we have to determine the moles of $CO_2$ gas.

$\text{ Moles of }CO_2=\frac{\text{ Mass of }CO_2}{\text{ Molar mass of }CO_2}=\frac{1.100g}{44g/mole}=0.025moles$

Now we have to calculate the moles of the oxygen gas.

Using ideal gas equation:

$PV=nRT$

As, the moles is an additive property. So,

$PV=(n_{O_2}+n_{CO_2})RT$

where,

P = pressure of gas = 608 mmHg = 0.8 atm

(conversion used : 1 atm = 760 mmHg)

V = volume of gas = 1 L

T = temperature of gas = 373 K

$n_{O_2}$ = number of moles of oxygen gas = ?

$n_{CO_2}$ = number of moles of carbon dioxide gas = 0.025 mole

R = gas constant = $0.0821L.atmK^{-1}mol^{-1}$

Now put all the given values in the ideal gas equation, we get:

$(0.8atm)\times (1L)=(n_{O_2}+0.025)mole\times (0.0821L.atmK^{-1}mol^{-1})\times (373K)$

$n_{O_2}=0.001124mole$

Now we have to calculate the mass of oxygen gas.

$\text{Mass of }O_2=\text{Moles of }O_2\times \text{Molar mass of }O_2$

$\text{Mass of }O_2=0.001124mole\times 32g/mole=0.03597g$

Therefore, the mass of oxygen present in the flask is 0.03597 grams.