Respuesta :
Answer: 2.5 grams
Explanation:
To calculate the moles, we use the equation:
[tex]\text{Number of moles}=\frac{\text{Given mass}}{\textMolar mass}}=\frac{2g}{4g/mol}=0.5moles[/tex]
Avogadro's Law: This law states that volume is directly proportional to the number of moles of the gas at constant pressure and temperature.
[tex]V\propto n[/tex] (At constant temperature and pressure)
[tex]\frac{V_1}{n_1}=\frac{V_2}{n_2}[/tex]
where,
[tex]V_1[/tex] = initial volume of gas = 2.00 L
[tex]V_2[/tex] = final volume of gas = 4.50 L
[tex]n_1[/tex] = initial number of moles = 0.5 moles
[tex]n_2[/tex] = final number of moles = ?
Now put all the given values in the above equation, we get the final pressure of gas.
[tex]\frac{2.00}{0.5}=\frac{4.50}{n_2}[/tex]
[tex]n_2=1.125moles[/tex]
Thus moles of helium added to the cylinder = (1.125-0.5)= 0.625 moles
Mass of helium added =[tex]moles\times {\text {Molar mass}}=0.625\times 4=2.5grams[/tex]
2.5 grams of helium were added to the cylinder if the volume was changed from 2.00 L to 4.50 L.
