Question

How many moles of oxygen gas are in a 650 mL flask at 1400 Torr and 385K

Answer 1

The number of moles of oxygen gas is 0.038 mol

Step-by-step explanation

Given that;

The volume of oxygen gas is 650mL

The pressure of the oxygen gas is 1400 torr

The temperature of the oxygen gas is 385K

Follow the steps below to find the number of moles of oxygen gas

Step 1; Assume the gas is an ideal gas

The ideal gas equation is given below

`\text{ PV = nRT}`

Where

P is the pressure

V is the volume

n is the number of moles

R is the universal gas constant

T is the temperature of the gas

Step 2; Convert the volume to Liters

Let x represents the volume of gas in liters

`\begin{gathered} \text{ 1mL }\rightarrow\text{ 0.001L} \\ \text{ 650mL }\rightarrow\text{ xL} \\ \text{ cross multiply} \\ \text{ 1mL }*\text{ xL }=\text{ 650mL }*\text{ 0.001L} \\ \text{ Isolate x} \\ \text{ xL = }\frac{650\cancel{mL}*0.001L}{1\cancel{mL}} \\ \text{ xL = }\frac{650*\text{ 0.001}}{1} \\ \text{ xL = 0.65L} \end{gathered}`

Step 3; Substitute the given data into the formula in step 1

`\begin{gathered} \text{ Recall, that R is 62.363 L.torr.mol}^(-1).K^(-1) \\ \text{ 1400}*\text{ 0.65 }=\text{ n }*\text{ 62.363}*\text{ 385} \\ \text{ 910 = 24,009.755n} \\ \text{ n = }(910)/(24,009.755) \\ \text{ n }=\text{ 0.038 mol} \end{gathered}`

Therefore, the number of moles of oxygen gas is 0.038 mol