Question

what is the pressure of a 1.0 l flask containing 0.60 g of he at 25°c? (r= 0.0821 l atm/ mol k)
15 atm
98 atm
7.3 atm
3.7 atm
none of the above

Explanation:

Step1: Calculate moles of He

Molar mass of He is 4.0 g/mol. Moles ($n$) = mass / molar mass = $0.60\ g / 4.0\ g/mol = 0.15\ mol$.

Step2: Convert temperature to Kelvin

$T = 25^\circ C + 273.15 = 298.15\ K$.

Step3: Use Ideal Gas Law ($PV = nRT$) to find $P$

Rearrange formula: $P = \frac{nRT}{V}$. Substitute values: $n = 0.15\ mol$, $R = 0.0821\ L\ atm/mol\ K$, $T = 298.15\ K$, $V = 1.0\ L$.
$P = \frac{0.15\ mol \times 0.0821\ L\ atm/mol\ K \times 298.15\ K}{1.0\ L} \approx 3.7\ atm$.

Answer:

3.7 atm (the option: 3.7 atm)