Respuesta :
Answer:
The reaction shifts from right to left. The new concentration of PCl₅ in equilibrium is 1.133 M.
Explanation:
The stress applied to the system is the addition of Cl₂. To offset this stress, some Cl₂ reacts with PCl₃ to produce PCl₅ until a new equilibrium is established.
The net reaction therefore shifts from right to left, that is,
PCl₅ (g) ← PCl₃ (g) + Cl₂ (g)
To work with the Kc expression, we need to convert the grams to moles. Since the volume of the flask is 1 liter, the moles can be expressed as molarity.
For PCl₅:
208.23 g ---------- 1 mol
3.74 g -------------- x= 1.80 x10⁻² mol ⇒ 1.80 x10⁻² M
For PCl₃:
137.33 g ---------- 1 mol
4.86 g ------------- x= 3.54 x10⁻² mol ⇒ 3.54 x10⁻² M
For Cl₂:
70.91 g ---------- 1 mol
3.59 g ----------- x= 5.06 x10⁻² mol ⇒ 5.06 x10⁻² M
Now, taking into account the shift of the equation, we make an ICE chart:
PCl₅ (g) ← PCl₃ (g) + Cl₂ (g)
i) 1.80 x10⁻² 3.54 x10⁻² 5.06 x10⁻²
c) +x -x +1.31 x10⁻² -x
e) 1.80 x10⁻² +x 3.54 x10⁻² -x 5.06 x10⁻²+1.31 x10⁻² -x
Now, we write the Kc formula:
Kc = [PCl₃] [Cl₂] / [PCl₅]
Kc = [ 3.54 x10⁻² -x] [5.06 x10⁻²+1.31 x10⁻² -x] / [1.80 x10⁻² +x]
After working with the expression, we find that x = 1.115.
Therefore, the new concentration of PCl₅ will be 1.133 M.
Answer:
The new concentration of PCl5 will be 0.0212637 M
Explanation:
Step 1: Data given
Mass of Cl2 added = 1.31 grams
Molar mass Cl2 = 70.9 g/mol
Original Equilibrium Mixture:
3.74 g PCl5
4.86 g PCl3
3.59 g Cl2
Volume = 1.0 L
Step 2: The balanced equation
PCl5(g) ⇆ PCl3(g) + Cl2(g)
Step 3: Calculate the original moles and molarity
Moles = mass / molar mass
Moles PCl5 = 3.74 grams / 208.23 g/mol
Moles PCl5 = 0.0180 moles
[PCl5] = 0.0180 M
moles PCl3 = 4.86 grams / 137.33 g/mol
moles PCl3 = 0.0354 moles
[PCl3] = 0.0354 M
moles Cl2 = 3.59 grams / 70.9 g/mol
moles Cl2 = 0.0506 moles
[Cl2] = 0.0506 M
the new mass Cl2 = 3.59 + 1.31 = 4.9 grams
moles Cl2 = 0.0691 moles
[Cl2]= 0.0691 M
The new concentration at the equilibrium
[PCl5] = 0.0180 + X M
[PCl3 ] = 0.0354 - X M
[Cl2] = 0.0691 - X M
Step 4: Calculate Kc
Kc = [Cl2][PCl3] / [PCl5]
Kc = (0.0506*0.0354)/0.0180
Kc = 0.0995
Step 5: Calculate [PCl5]
Kc = 0.0995 = ((0.0691 - X)(0.0354 - X)) / (0.0180 + X)
X = 0.0032637
[PCl5] = 0.0180 + 0.0032637 M = 0.0212637 M
[PCl3 ] = 0.0354 - 0.0032637 M = 0.0321363 M
[Cl2] = 0.0691 - 0.00313 M = 0.0658363
The new concentration of PCl5 will be 0.0212637 M
