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4
0.16/0.04=4.
University admission · Other / specialist pathway · Chemistry
Chemistry for the selected science pathway
Solve equilibrium and reaction-quantity questions with stated models.
Original Model Test for Exam unit. These questions and suggested practice times are independent Kidemy material, not an official or past paper. Choose modules for the target programme; all listed subjects are not required for every applicant.
Learn the idea
A reaction quotient describes current composition under a defined expression; the equilibrium constant describes equilibrium at a given temperature. Catalysts change rates and do not change that equilibrium constant. Mole ratios still come from a balanced equation.
Worked example
For H2+I2⇌2HI, Kc=[HI]²/([H2][I2]). With equilibrium concentrations 0.4, 0.2 and 0.2 mol/dm³ respectively, Kc=4 in the concentration expression.
- Write the equation and expression.
- Use equilibrium rather than arbitrary concentrations for K.
- Separate rate effects from equilibrium position.
Your written practice
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No. It accelerates both directions without changing the equilibrium constant.
Review both the conclusion and its reason. It accelerates both directions without changing the equilibrium constant.
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0.25
10/40=0.25.
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The equilibrium constant depends on temperature.
Do not treat K as unchanged under every condition.
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The response depends on the change in gas mole counts and the reaction; equal gas mole counts need not shift for this reason.
State the gas-phase condition.
Chemistry model test
Write equilibrium expressions and one mole-ratio solution.
Review with a guardian or teacher
- Use correct powers.
- State temperature relevance.
- Avoid unsupervised chemical experiments.
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