Calculate the molar mass of a gas given its pressure, temperature, and density. Also, calculate the volume of helium in liters.

We are given:
Pressure ($P$) = 1.34 atm
Temperature ($T$) = 303 K
Density ($\rho$) = 1.77 g/L
Gas constant ($R$) = 0.08206 L·atm/(mol·K)

The ideal gas law is $PV = nRT$.
We know that the number of moles $n = \frac{m}{M}$, where $m$ is mass and $M$ is molar mass.
Substituting $n$ into the ideal gas law: $PV = \frac{m}{M}RT$.
Rearranging for density ($\rho = \frac{m}{V}$): $P = \frac{m}{V} \frac{RT}{M} \implies P = \rho \frac{RT}{M}$.
Solving for molar mass ($M$):

Rounding to three significant figures:

The molar mass of the gas is $\boxed{\text{32.8 g/mol}}$.

We are given:
Volume ($V$) = 7240 ft$^3$
Pressure ($P$) = 745 torr
Temperature ($T$) = 21 °C
Conversion: 1 ft$^3$ = 28.3 L
Gas: Helium (He)
Molar mass of Helium ($M_{He}$) = 4.00 g/mol
Gas constant ($R$) = 0.08206 L·atm/(mol·K)

Convert volume from ft$^3$ to L:

Convert pressure from torr to atm:

Convert temperature from °C to K:

The ideal gas law is $PV = nRT$.
Solving for $n$:

Mass ($m$) = number of moles ($n$) $\times$ molar mass ($M_{He}$)

Rounding to three significant figures:

The mass of helium required is $\boxed{\text{33300 g}}$.