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4
1+3.
Class 9 · English Medium · Cambridge · Chemistry
Reactions, acids, bases and salts
Predict an equilibrium response while separating concentration from rate.
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Learn the idea
An equilibrium response is evaluated under specified changes and conditions. Adding a reactant changes the reaction quotient. At fixed temperature the equilibrium constant stays the same; the composition can shift until the ratio again matches it. A catalyst changes the approach rate rather than K.
Worked example
For N2+3H2⇌2NH3, compression at fixed temperature favours the side with fewer gas moles in the ideal model:2 product moles versus4 reactant moles. This direction alone does not quantify the yield.
- Write the equilibrium and gas counts.
- State the imposed change.
- Separate position, constant and rate.
Your written practice
Show your working on paper and enter your answer here. If it does not match, compare the model and try again.
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2
The NH3 coefficient is 2.
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unchanged
It changes rates, not the equilibrium constant.
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The product side has fewer gas moles; the system changes composition toward that side under the imposed volume decrease.
State fixed temperature and gaseous species.
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The initial composition, equilibrium constant and extent conditions are also needed.
Distinguish direction from magnitude.
Apply the idea
Compare three changes to one equilibrium, stating which quantities remain fixed.
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- Use the stated evidence or givens.
- Show reasoning rather than only a result.
- Review and explain one correction.
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