Question

(The question is in the photo ) How many molecules are contained in 815 mL of O2 gas at 180C and 759 torr?Answer in units of molec. Please leave all the numbers after the decimal in the final answer

Answer 1

To solve this problem we have to use ideal gas law.

First convert mL to L, torr to atm and °C to K:

`\begin{gathered} 815mL\cdot(1L)/(1000mL)=0.815L \\ 759torr\cdot(1atm)/(760torr)=0.998atm \\ K=180+273.15=453.15 \end{gathered}`

Use the ideal gas law and solve for n:

`\begin{gathered} n=(P\cdot V)/(R\cdot T) \\ n=\frac{0.998atm\cdot0.815L}{0.082\frac{\text{atmL}}{\text{molK}}\cdot453.15K} \\ n=0.021889\text{mol} \end{gathered}`

Use Avogadro's number to find the number of molecules in the amount of moles obtained:

`0.021889\text{mol}\cdot(6.022*10^(23)molecules)/(1mol)=1.318155*10^(22)molecules`

It means that there are 1.318155x10^22 molecules contained in 815mL.