At dynamic equilibrium, the rates of the forward and reverse reactions are:
Equal
Zero
The forward rate is greater
The reverse rate is greater
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WhyAt dynamic equilibrium the forward and reverse reactions occur at equal rates, so the concentrations of reactants and products remain constant.
2Multiple choice · Easy
For a gaseous equilibrium, increasing the total pressure shifts the position of equilibrium towards the side with:
Fewer moles of gas
More moles of gas
The heavier molecules
The solids
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WhyBy Le Chatelier's principle, increasing pressure shifts the equilibrium towards the side with fewer moles of gas to reduce the pressure.
3Multiple choice · Medium
Increasing the temperature of an equilibrium shifts it in the direction of the:
Endothermic reaction
Exothermic reaction
Side with fewer moles
Side with the catalyst
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WhyRaising the temperature shifts the equilibrium in the endothermic direction, which absorbs the added heat.
4Multiple choice · Medium
What effect does adding a catalyst have on the position of equilibrium?
No effect on the position
Shifts it to the products
Shifts it to the reactants
Stops the reaction
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WhyA catalyst speeds up the forward and reverse reactions equally, so equilibrium is reached faster but its position is unchanged.
5Multiple choice · Medium
Removing a product from an equilibrium mixture causes the equilibrium to shift:
Towards the products (forward)
Towards the reactants (backward)
It stops
There is no change
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WhyBy Le Chatelier's principle, removing product shifts the equilibrium to the right (forward) to replace the product.
6Multiple choice · Hard
In the Haber process, $\text{N}_{2}(g) + 3\text{H}_{2}(g) \rightleftharpoons 2\text{NH}_{3}(g)$ ($\Delta H < 0$), the yield of ammonia is increased by:
High pressure and low temperature
Low pressure and high temperature
High pressure and high temperature
Removing the catalyst
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WhyThe forward reaction is exothermic and reduces gas moles, so a low temperature and high pressure increase the yield of ammonia (a moderate temperature is used in practice for rate).
7Fill in the blank · Easy
A reaction that can proceed in both the forward and reverse directions is described as .
Answer:
reversible
WhyA reversible reaction is shown with the equilibrium arrow $\rightleftharpoons$ and can reach a dynamic equilibrium.
8Fill in the blank · Medium
A value of the equilibrium constant much greater than 1 ($K_{c} \gg 1$) means the position of equilibrium favours the .
Answer:
products / product
WhyA large $K_{c}$ means the equilibrium concentrations of products are much greater than those of reactants, so products are favoured.
9Multiple choice · Medium
What is the equilibrium constant expression Kc for N2(g) + 3 H2(g) <-> 2 NH3(g)?
Kc = [NH3]^2 / ([N2][H2]^3)
Kc = [N2][H2]^3 / [NH3]^2
Kc = [NH3] / ([N2][H2])
Kc = [NH3]^2 / ([N2] + 3[H2])
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WhyKc = [NH3]^2 / ([N2][H2]^3), with coefficients as exponents.
10Multiple choice · Easy
A large value of Kc indicates that at equilibrium the mixture contains mostly
products
reactants
only solids
equal amounts of reactants and products
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WhyA large Kc means the position of equilibrium lies to the right, favouring products.
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