# A 4.44 L container holds 15.4 g of oxygen at 22.55°C. What is the pressure?

Jun 18, 2017

We use the Ideal Gas Equation to get...........$P = 2.63 \cdot a t m$

#### Explanation:

$P = \frac{n R T}{V} = \frac{\frac{15.4 \cdot g}{32.00 \cdot g \cdot m o {l}^{-} 1} \times 0.0821 \cdot \frac{L \cdot a t m}{K \cdot m o l} \times 295.7 \cdot K}{4.44 \cdot L} =$

$2.63 \cdot a t m$.

Do the units cancel out to give an answer in $a t m$? Do they? Don't assume that I haven't made a mistake!

How did I do this? Well for (i) I know that oxygen is a binuclear gas, i.e. ${O}_{2}$; in fact all the elemental gases (save for the Noble Gases) are BINUCLEAR.....and thus I used a molecular mass of $32.00 \cdot g \cdot m o {l}^{-} 1$ for dioxygen gas.......

And (ii) I knew the gas constant was............... $0.0821 \cdot L \cdot a t m \cdot {K}^{-} 1 \cdot m o {l}^{-} 1$.

And (iii) I knew the relationship between ""^@C and $\text{degrees Kelvin}$.

These data (well (ii) and (iii)) need not be remembered, as they should be provided (with various units) in a chemistry exam. You still need to know how to use the appropriate gas constant, $R$.