What is the total pressure exerted by a mass of #2.27*g# of oxygen gas, and a mass of #0.636*g# of helium gas, if the container had a volume of #6.26*L#, and the gases were at a temperature of #51# #""^@C#?

Question

Naomi Aronson · Accepted Answer

Dalton's Law of Partial Pressures states that the pressure exerted by a component in a gaseous mixture, is precisely the same as it would exert if it ALONE occupied the container,

The sum of the individual partial pressures is the total pressure. As stated above: #P_"Total" = P_"oxygen" + P_"helium"# #=# #(R*T*n_"oxygen")/V+(R*T*n_"helium")/V# #=# #(RT)/V{n_"oxygen" + n_"helium"}# #=# #(RT)/V{(2.27*g)/(32.0*g*mol^-1)+(0.636*g)/(4.0*g*mol^-1)}# #R=0.0821*L*atm*K^-1*mol^-1; T=326K; V=6.26L#

Peyton Adams · Answer

undefined To find the total pressure, first, calculate the moles of each gas using the ideal gas law. Then, use Dalton's law of partial pressures to find the partial pressures of each gas. Finally, sum the partial pressures to find the total pressure.

Moles of oxygen gas (O2):
n(O2) = mass / molar mass
n(O2) = 2.27 g / (32.00 g/mol) = 0.0709375 mol

Moles of helium gas (He):
n(He) = mass / molar mass
n(He) = 0.636 g / (4.00 g/mol) = 0.159 mol

Partial pressure of oxygen gas:
P(O2) = n(O2) * R * T / V
P(O2) = (0.0709375 mol) * (0.0821 atm·L/mol·K) * (51 + 273.15 K) / 6.26 L = 0.9167 atm

Partial pressure of helium gas:
P(He) = n(He) * R * T / V
P(He) = (0.159 mol) * (0.0821 atm·L/mol·K) * (51 + 273.15 K) / 6.26 L = 2.011 atm

Total pressure:
P(total) = P(O2) + P(He) = 0.9167 atm + 2.011 atm = 2.9277 atm