GCE A-Level (Singapore) Fundamental Equilibrium Concepts — practice questions — page 2

Explore 33 free Fundamental Equilibrium Concepts questions in GCE A-Level (Singapore) Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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Fundamental Equilibrium Concepts questions and exercises with answers

Showing questions 31–33 of 33.

For N2 + 3H2 forming 2NH3 with Kc = 6.00 x 10^-2, [N2] = 4.26 M and [H2] = 2.09 M. What is [NH3]?Read the answer and worked solution →Knock out the false equilibrium claimsRead the answer and worked solution →Swipe each change by the way it shiftsRead the answer and worked solution →

Worked practice questions

For N2 + 3H2 forming 2NH3 with Kc = 6.00 x 10^-2, [N2] = 4.26 M and [H2] = 2.09 M. What is [NH3]?

0.53 M
2.33 M
1.53 M
0.77 M

Show answer and solution

Correct answer: C. 1.53 M

1. Write the expression: Kc = [NH3] squared divided by ([N2] x [H2] cubed). 2. Cube the hydrogen term: 2.09 x 2.09 x 2.09 = 9.13. 3. Multiply by the nitrogen term: 4.26 x 9.13 = 38.9. 4. Rearrange: [NH3] squared = Kc x 38.9 = 6.00 x 10^-2 x 38.9 = 2.33. 5. Take the square root: the root of 2.33 is 1.53. 6. So the ammonia concentration is 1.53 mol per litre. 7. Quoting 2.33 M is the trap of stopping before the square root is taken. 8. Using the hydrogen term unsquared, or uncubed, gives the other two offered values. _Source: OpenStax Chemistry (CC BY 4.0), Ch 13 "Fundamental Equilibrium Concepts", section 13.4 Equilibrium Calculations_

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Knock out the false equilibrium claims

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Questions

Question
Three of these claims about a disturbed equilibrium are false.
Choices
1. Item
  A catalyst leaves the constant unchanged
  Correct
  Yes
2. Explanation
  A gas outside the equilibrium leaves every partial pressure alone.
  Item
  Adding an unreactive gas shifts it
3. Explanation
  Only reactions that change the number of gas molecules respond.
  Item
  A pressure rise shifts any gas reaction
4. Explanation
  Heating a heat releasing reaction drives it back to reactants.
  Item
  Heating always makes more product

Instructions

Tap the three false statements about disturbing a chemical equilibrium to clear them.

_Source: OpenStax Chemistry, Ch 13 Fundamental Equilibrium Concepts, section Catalysts Do Not Affect Equilibrium_

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Swipe each change by the way it shifts

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Left

More product

Items

Item
Add more hydrogen
Answer
More product
Item
Add more iodine
Answer
More product
Item
Add more product
Answer
More reactant
Item
Raise temperature
Answer
More reactant
Item
Remove the product
Answer
More product
Item
Remove a reactant
Answer
More reactant
Item
Cool the mixture
Answer
More product

Right

More reactant

Instructions

In a heat releasing reaction, swipe left if the change makes more product, right for more reactant.

_Source: OpenStax Chemistry, Ch 13 Fundamental Equilibrium Concepts, section 13.3 Shifting Equilibria: Le Châtelier's Principle_