What is the mass of a sample of O₂ gas, which has a pressure of 740. mmHg, at a temperature of 25 °C, in a volume of 250. mL?

Question

Quizplus · Accepted Answer

To solve this problem, we need to use the combined gas law:

(P₁V₁)/T₁ = (P₂V₂)/T₂

where P is the pressure, V is the volume, and T is the temperature.

We can use the given pressure, volume, and temperature to find the initial conditions (P₁, V₁, and T₁) of the gas. Then, we can use the ideal gas law:

PV = nRT

where P is the pressure, V is the volume, n is the amount of substance (in moles), R is the ideal gas constant, and T is the temperature.

We can rearrange this equation to solve for n:

n = PV/RT

Once we know the amount of substance, we can use the molar mass of O₂ (32.00 g/mol) to find the mass of the sample.

Putting it all together:

P₁ = 740. mmHg
V₁ = 250. mL
T₁ = 25 °C + 273.15 = 298.15 K (note that we converted from Celsius to Kelvin)
T₂ = T₁ (since the gas is not undergoing a change in temperature)
V₂ = V₁ (since the gas is not undergoing a change in volume)

Using the combined gas law, we can solve for P₂:

P₂ = (P₁V₁)/V₂ = (740. mmHg x 250. mL)/250. mL = 740. mmHg

Now we have:

P₂ = 740. mmHg
V₂ = 250. mL
T₂ = 298.15 K

Using the ideal gas law, we can solve for the amount of substance:

n = (740. mmHg x 0.250 L)/(0.082057 L·atm/mol·K x 298.15 K) = 0.0100 mol

Finally, we can find the mass of the sample:

mass = n x molar mass = 0.0100 mol x 32.00 g/mol = 0.320 g

Therefore, the answer is A) 0.318 g. Note that this answer is slightly different from the calculated value due to rounding.

What Is the Mass of a Sample of O₂ Gas