3.2.3 - Chemical Equilibrium Flashcards

1
Q

What does dynamic equilibrium mean?

A

It occurs when the rate of the forward reaction equals the rate of the reverse reaction

And the concentration of reactants and products remain constant in a closed system

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2
Q

Changing what factors can alter the position of equilirbrium?

A

Concentration of reactants or products
Pressure
Temperature

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3
Q

Explain the Le Chatelier’s principle

A

If a system at equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance

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4
Q

In the equation

CH4 (g) + H2O (g) CO (g) + 3 H2 (g)

Delta H = +210 KJ mol -1

What effect would increasing the temperature have on the position of equilibrium?

A

The equilibirum position shifts to the right.

This is because the forward reaction is endothermic. Yield of hydrogen increases

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5
Q

In the equation

CH4 (g) + H2O (g) CO (g) + 3 H2 (g)

Delta H = +210 KJ mol -1

What effect would increasing the pressure have on the position of equilibrium?

A

The equilibrium position shifts to the left

This is because the forward reaction produces more moles of gas than the reverse reaction ( 4 moles of product, 2 moles of reactant). Therefore, the yield of of hydrogen decreases

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6
Q

In the equation

CH4 (g) + H2O (g) CO (g) + 3 H2 (g)

Delta H = +210 KJ mol -1

Suggest and explain why an industrial chemist may use a high pressure for this production of hydrogen for the above reaction?

A

The high pressure increases the collision frequency thus increasing the rate of reaction

This is a compromise pressure between an economically viable rate of reaction and a slightly lower yield of hydrogen

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7
Q

What effect does a catalyst have on the position of equilibirum?

A

No effect

Because the catalyst rate of forward ad reverse reactions equally

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8
Q

What condition affects the value of Kc?

A

Temperature

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9
Q

For the reaction below, deduce an expression for Kc

2[A] + 3[B] + [C] –> [D] + 4[E]

A

Kc = [D][E]^4 / [A]^2[B]^3[C]

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10
Q

Deduce the units for the value of

kc = [D][E]^4 / [A]^2[B]^3[C]

A

mol -1 dm-3

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11
Q

What type of system is Kc relevant for?

A

Homogenous systems in equilibrium

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12
Q

What does Kc being greater or less than 1 suggest for the position of equilibrium?

A

Greater than 1 = over to the right

Less than 1 = over to the left

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13
Q

What effect does decreasing the temperature of an endothermic reaction have on Kc?

A

Kc decreases

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14
Q

What effect does increasing the temperature of an endothermic reaction have on Kc?

A

Kc increases

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15
Q

What effect does decreasing the temperature of an exothermic reaction have on Kc?

A

Kc increases

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16
Q

What effect does increasing the temperature of an exothermic reaction have on Kc?

A

Kc decreases