# At constant temperature and volume, a 0.2*mol quantity of helium gas exerts a pressure of 22.7*kPa. HALF this molar quantity of oxygen gas is injected, what is P_"Total"?

## $A .$ 34.05*kPa; $B .$ 69.10*kPa; $C .$ 25.05*kPa; $D .$ $\text{Impossible to determine.}$

May 29, 2017

$\text{Option A}$

#### Explanation:

$\text{Dalton's Law of Partial Pressures}$ states that in a gaseous mixture, the partial pressure, ${P}_{1}$, exerted by a gaseous component is the same as the pressure it would exert if it ALONE occupied the container. The total pressure, ${P}_{\text{Total}}$, is the sum of the individual partial pressures:

${P}_{\text{Total}} = {P}_{1} + {P}_{2} + \ldots \ldots \ldots \ldots . {P}_{n}$

Here, $0.2 \cdot m o l$ quantity of helium gas exerts a $22.7 \cdot k P a$ pressure, so if we inject a $0.1 \cdot m o l$ quantity of dioxygen gas it will exert a proportional pressure, i.e. proportional to its molar quantity, a pressure of $11.35 \cdot k P a$. ${P}_{\text{Total}} = \left(22.7 + 11.35\right) \cdot k P a = A$, as required.....

Happy?

Why doesn't the helium gas react with the dioxygen gas? Dioxygen gas is fiercely reactive.