DSE Chemistry: Chemical Equilibrium — Practice Questions & Answers
Reversible reactions and dynamic equilibrium, the effects of concentration, pressure and temperature predicted by Le Chatelier's principle, and industrial conditions.
294 practice questions available for this topic — here are 10 with full answers and explanations.
Which statement about a chemical system at dynamic equilibrium is correct?
The rates of the forward and backward reactions are equal
Both reactions have stopped
The amounts of reactants and products are always equal
Only the backward reaction occurs
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WhyAt dynamic equilibrium the forward and backward reactions occur at equal rates, keeping concentrations constant.
2Multiple choice · Medium
Increasing the reaction temperature does NOT increase the yield of every reversible reaction because
for an exothermic forward reaction a higher temperature lowers the yield
temperature never affects equilibrium
a higher temperature always increases the yield
temperature only affects catalysts
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WhyRaising temperature shifts an exothermic forward reaction towards the reactants, lowering its yield even though equilibrium is reached faster.
3Multiple choice · Hard
For the equilibrium Fe3+(aq) + SCN-(aq) reversible Fe(SCN)2+(aq), adding Na3PO4(s) removes Fe3+ as insoluble FePO4. The equilibrium position will
shift to the left
shift to the right
remain unchanged
stop completely
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WhyRemoving Fe3+ shifts the equilibrium to the left to replace it, so Fe(SCN)2+ decomposes.
4Fill in the blank · Medium
When writing an equilibrium constant Kc expression, pure solids and pure liquids are .
Answer:
omitted / left out / excluded
WhyOnly species whose concentrations can vary are included.
5Fill in the blank · Easy
The value of the equilibrium constant Kc changes only when the is changed.
Answer:
temperature
WhyConcentration and pressure changes do not alter Kc.
6Fill in the blank · Medium
Removing a product from an equilibrium mixture shifts the position of equilibrium to the to replace it.
Answer:
right / products / product side
WhyThis follows Le Chatelier's principle.
7Multiple choice · Medium
For X2(g) + 3Y2(g) reversible 2XY3(g), which combination shows the effect of a catalyst on the rate of forward reaction, rate of backward reaction and the yield of XY3?