A eudiometer is used to collect hydrogen gas in a chemical reaction, as in your Exp 7. The volume of the gas in the tube (when pressure is held constant) is 479.10 mL. The pressure of the atmosphere during the experiment is 758.3 mmgHg, and the temperature of the water and gas is
19.0*C. The water vapor pressure at this temperature is 16.5 torr.
Calculate the mass of hydrogen, in mg, collected.

39.29 mg

Explanation:

Step 1: Calculate the partial pressure of hydrogen

The pressure of the atmosphere is equal to the sum of the partial pressures of the water and the hydrogen. (1 Torr = 1 mmHg)

P = pH₂O + pH₂

pH₂ = P - pH₂O = 758.3 mmHg - 16.5 mmHg = 741.8 mmHg

We will convert it using the conversion factor 1 atm = 760.0 mmHg.

741.8 mmHg × 1 atm/760.0 mmHg = 0.9761 atm

Step 2: Convert 19.0 °C to Kelvin

We will use the following expression.

K = °C + 273.15 = 19.0 + 273.15 = 292.2 K

Step 3: Calculate the mass of hydrogen

First, we will calculate the moles of hydrogen using the ideal gas equation.

P × V = n × R × T

n = P × V / R × T

n = 0.9761 atm × 0.47910 L / (0.08206 atm.L/mol.K) × 292.2 K = 0.01950 mol

The molar mass of hydrogen is 2.015 g/mol. The mass of hydrogen is:

0.01950 mol × 2.015 g/mol = 0.03929 g = 39.29 mg