# A 1.50 liter flask at a temperature of 25°C contains a mixture of .158 moles of methane, .09 moles of ethane, and .044 moles of butane. What is the total pressure of the mixture inside the flask?

Oct 8, 2016

$P = \frac{n R T}{V} \cong 5 \cdot a t m$

#### Explanation:

Dalton's law of partial pressures holds that in a gaseous mixture, (i) the partial pressure of any component gas is the same as the pressure it would exert if it ALONE occupied the container; and (ii) that the total pressure is the sum of the individual partial pressures.

Thus ${P}_{\text{total}}$ $=$ ${P}_{\text{methane"+P_"ethane"+P_"butane}}$, and if we (reasonably) assume ideality, then:

${P}_{\text{total}}$ $=$ $\frac{{n}_{\text{total}} \times 0.0821 \cdot L \cdot a t m \cdot {K}^{-} 1 \cdot m o {l}^{-} 1 \times 298 \cdot K}{1.50 \cdot L}$

where $\left({n}_{\text{total"=n_"methane"+n_"ethane"+n_"butane}}\right)$ $=$

$\left(0.158 + 0.09 + 0.044\right) \cdot m o l$ $=$ $0.292 \cdot m o l$

And so, ${P}_{\text{total}}$ $\cong$ $5 \cdot a t m$. You will be able to make a better estimate.