A mixture of 0.47 mole of H2 and 3.59 moles of HCl is heated to 2800C. Calculate the equilibrium partial pressures of H2 Cl2 and HCl if the total pressure is 2.00 atm. For the reaction Kp is 193 at 2800C.
H2(g) +Cl2(g) = 2HCl (g)
I know that I need to find the total numbers of moles, but I do not know how to find how many moles there is in Cl2.
To start, you need to know pressures initially. I would solve for mole fraction H2 and mole fraction HCl. That will be
mole fraction HCl = moles HCl/total moles
mole fraction H2 = moles H2/total moles.
Then PHCl = mole fraction HCl x total P.
and PH2 = mole fraction H2 x total P.
Then set up an ICE chart, substitute into Kp expression, and solve for partial pressures of each at equilibrium conditions.
Post your work if you get stuck.
how would you find total number of moles?
To determine the number of moles of Cl2, we can use the stoichiometry of the balanced equation. According to the equation:
H2(g) + Cl2(g) -> 2HCl(g)
We can see that the mole ratio between H2 and Cl2 is 1:1, meaning that for every mole of H2, there is exactly one mole of Cl2 consumed. In this case, we know that there are 0.47 moles of H2, so there must also be 0.47 moles of Cl2.
Now that we know the number of moles of H2, Cl2, and HCl, we can proceed to calculate the equilibrium partial pressures.
To find the equilibrium partial pressures, we can use the ideal gas law, which states: PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant (0.0821 L.atm/mol.K), and T is the temperature in Kelvin.
Given that the total pressure is 2.00 atm and we want to find the partial pressures of H2, Cl2, and HCl, we can set up the following equations:
PH2 + PCl2 + PHCl = PTOTAL (equation 1)
We also need to consider that for every 2 moles of HCl formed, 1 mole of H2 and 1 mole of Cl2 react. Therefore, we can express the equilibrium partial pressures of H2, Cl2, and HCl in terms of x (the number of moles of HCl formed):
PH2 = 0.47 - x
PCl2 = 0.47 - x
PHCl = 2x
Substituting these expressions into equation 1, we get:
(0.47 - x) + (0.47 - x) + 2x = 2.00
Simplifying the equation, we have:
0.94 + x = 2.00
x = 2.00 - 0.94
x = 1.06 moles
Now that we have obtained the value of x, which represents the number of moles of HCl formed, we can use this information to find the equilibrium partial pressures of H2, Cl2, and HCl.
PH2 = 0.47 - x = 0.47 - 1.06 = -0.59 atm (discarded since it is not physically meaningful)
PCl2 = 0.47 - x = 0.47 - 1.06 = -0.59 atm (discarded since it is not physically meaningful)
PHCl = 2x = 2 * 1.06 = 2.12 atm
Therefore, at equilibrium, the partial pressure of H2 is not meaningful (as it is negative), the partial pressure of Cl2 is not meaningful (as it is negative), and the partial pressure of HCl is 2.12 atm.