# A student collects 425 mL of oxygen at a temperature of 24°C and a pressure of 0.899 atm. How many moles of oxygen did the student collect?

${n}_{{O}_{2}} = 0.0157 \cdot m o l$
We solve for $n$ in the old Ideal Gas equation...and perforce we use units of $\text{absolute temperature....}$
$n = \frac{P V}{R T} = \frac{0.899 \cdot a t m \times 425 \cdot m L \times {10}^{-} 3 \cdot L \cdot m {L}^{-} 1}{0.0821 \cdot \frac{L \cdot a t m}{K \cdot m o l} \times 297.15 \cdot K}$
$\equiv 0.0157 \cdot m o l$...and what mass of dioxygen does this represent?