Өнеркәсіптік тепе-теңдік. Тепе-теңдік константасы Kc. Химия, 10 сынып, дидактикалық материал.

Topic: Equilibrium HL

Calculating equilibrium concentration K_c

General reaction: aA + bB ⇌ eE + fF

At equilibrium:

K_c = [E]^e [F]^f If K_c >> 1 the forward reaction is favoured

[A]^a [B]^b If K_c << 1 the backward reaction is favoured

Therefore, to find K_c only the equilibrium concentrations of the reactants and products can be used.

Steps involving both reactants and products:

• Molar ratio (from the reaction equation)
• Initial moles/mol
• Equilibrium moles/mol (decreasing reactants and increasing products from initial moles or using the formula moles = equilibrium concentration x volume given in Q
• Equilibrium concentration/mol dm^-3

Question 1

4.00 mol of HI(g) was admitted to an evacuated 2.00 dm³ reaction vessel and allowed to reach equilibrium at a constant temperature, according to the equation:

2HI(g) ⇌ H₂(g) + I₂(g)

At equilibrium, 0.250 mol of I₂ had formed.

• Determine the equilibrium concentration of all species at this temperature
• Calculate the equilibrium constant for the reaction

a)

 HIH₂I₂

Molar ratio

Initial moles

Equilibrium moles

Equilibrium concentration

b) K_c =

Question 2

1.800 mol of ammonia is introduced into an evacuated 5.00 dm³ vessel and allowed to come to equilibrium. The concentration of nitrogen at equilibrium was determined to be 0.0435 mol dm^-3. Calculate the equilibrium constant for the reaction shown, given that the temperature remained constant throughout.

2NH₃(g) ⇌ N₂(g) + 3H₂(g)

 NH₃N₂H₂

Molar ratio

Initial moles нач моль 1,800

Equilibrium moles равн моль

Equilibrium concentration 0,0435

K_c =

Question 3

1.50 mol of carbon monoxide and 0.500 mol of chlorine gas are introduced into an evacuated 10.0 dm³ vessel at 700 K. When the reaction reaches equilibrium, the concentration of phosgene (COCl₂) is 0.0485 mol dm³. Calculate the equilibrium constant for the reaction at this temperature. The reaction equation is:

CO(g) + CL₂(g) ⇌ COCl₂(g)