Question

An experiment shows that a 250- mL gas sample has a mass of 0.435 g at a pressure of 743 mm Hg and a temperature of 29 C.What is the molar mass of the gas?

Answer 1

The molar mass of the gas is 43.5g/mol.

Step-by-step explanation:

The given information of the gas from the exercise is:

- Volume (V): 250mL (0.25L)

- Mass: 0.435g

- Pressure (P): 743mmHg (1atm)

- Temperature (T): 29°C (302K)

1st) We can use the Ideal Gases formula to calculate the number of moles of the gas, remember to convert the units to atm, liters and Kelvin:

`\begin{gathered} P*V=n*R*T \\ 1atm*0.25L=n*0.082(atm*L)/(mol*K)*302K \\ 0.25atm*L=n*25(atm*L)/(mol) \\ (0.25atm*L)/(25(atm*L)/(mol))=n \\ 0.01mol=n \end{gathered}`

2nd) Now we can calculate the molar mass of the gas using the mass and the 0.01 moles, with a mathematical rule of three:

`\begin{gathered} 0.01mole-0.435g \\ 1mole-x=(1mole*0.435g)/(0.01mole) \\ x=43.5g \end{gathered}`

Finally, the molar mass of the gas is 43.5g/mol.