Lesson Worksheet: The Equilibrium Constant for Concentration Chemistry

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In this worksheet, we will practice constructing and calculating the equilibrium constant for concentration.

Q1:

Ammonia can be produced by the reaction between hydrogen and nitrogen gas that is represented by the following equation: 3H+N2NH223

5.00 mol of nitrogen gas and 5.00 mol of hydrogen gas are placed in a sealed vessel that has a volume of 20.00 dm3 at 500 K. At equilibrium, only 0.25 mol of nitrogen would be converted into ammonia.

Calculate the value of 𝐾 at this temperature, giving the answer to 3 decimal places.

Q2:

At equilibrium, 𝐾=32⋅moldm at 325 K for the following reaction involving oxides of sulfur: 2SO()+O()2SO()223ggg

Find the value of 𝐾, including units, at 325 K for the following reaction:

2SO()2SO()+O()322ggg

Q3:

The example equation 𝐾=[][][][]ABCD

shows how different chemical species, such as A, B, C, and D, are often enclosed in square brackets in equilibrium constant calculations.

What do the square brackets indicate?

  • AThe concentration measured in g⋅L−1
  • BThe partial pressure measured in kPa
  • CThe amount of substance measured in mol
  • DThe concentration measured in mol⋅L−1
  • EThe partial pressure measured in atm

Q4:

The following equation shows the decomposition of the salt ammonium carbamate at room temperature back into carbon dioxide and ammonia:

NH[HNCO]()2NH()+CO()42232sgg

A 6 g sample of ammonium carbamate was placed in an evacuated 200 mL flask. After equilibrium was established, 3.4 mg of CO2 was present in the flask. Taking the molar mass of CO2 to be 44.01 g/mol, calculate the value of 𝐾 for this decomposition at room temperature, giving your answer to two decimal places and in scientific notation.

  • A2.31×10 mol3⋅dm−9
  • B7.73×10 mol3⋅dm−9
  • C5.97×10 mol3⋅dm−9
  • D5.76×10 mol3⋅dm−9
  • E2.98×10 mol3⋅dm−9

Q5:

The equilibrium of a chemical reaction can be expressed by 𝐾, the equilibrium constant for concentration.

Find the correct equation for 𝐾 for the reaction shown between nitrogen and hydrogen:

3H+N2NH223

  • A𝐾=2[NH]3[H][N]322
  • B𝐾=[NH][H][N]322
  • C𝐾=[NH][H][N]32232
  • D𝐾=[NH][H][N]32232
  • E𝐾=[NH][H][N]33222

Q6:

For the following equilibrium showing the hydrolysis of an ester, find the correct equation for 𝐾: CHCOOCH+HOCHCOOH+CHOH33233

  • A𝐾=[CHCOOH][CHOH][CHCOOCH][HO]33332
  • B𝐾=[CHCOOH][CHOH][CHCOOCH][HO]33332
  • C𝐾=[CHOH][HO][CHCOOCH][CHCOOH]32333
  • D𝐾=[CHCOOCH][CHCOOH][HO][CHOH]33323
  • E𝐾=[CHCOOCH][HO][CHCOOH][CHOH]33233

Q7:

Find the units for the following 𝐾 equation: 𝐾=[HI][H][I]222

  • ANo units
  • Bmol⋅dm−3
  • Cmol−1⋅dm3
  • Dmol2⋅dm−6
  • Emol−2⋅dm6

Q8:

Silver ions can be reduced by iron(II) ions in the following net ionic equation:

Fe()+Ag()Fe()+Ag()2++3+aqaqaqs

What is the correct equation for 𝐾 for this reaction?

  • A𝐾=[Fe][Ag][Fe][Ag]3+2++
  • B𝐾=[Fe]Ag[Fe][Ag]3+2++n
  • C𝐾=[Fe][Fe][Ag]3+2++
  • D𝑛×𝐾=Ag[Fe][Fe][Ag]3+2++
  • E𝐾=[Fe][Ag][Fe][Ag]2++3+

Q9:

Consider the general reaction shown:

𝑎+𝑏𝑐+𝑑ABCD

What is the expression for the equilibrium constant for the reversible reaction of this general reaction? Take [A] and [B] to be the molar concentrations of the reactants, [C] and [D] to be the molar concentrations of the products, and 𝑎, 𝑏, 𝑐, and 𝑑 to be the stoichiometric coefficients in the balanced equation.

  • A𝐾=𝑐𝑑𝑎𝑏[C][D][A][B]
  • B𝐾=[C][D][A][B]
  • C𝐾=[A][B]
  • D𝐾=[A][B][C][D]
  • E𝐾=[C][D]

Q10:

Consider the equilibrium reaction

N()+O()2NO()22ggg

How would we express 𝐾 for this equilibrium reaction?

  • A𝐾=[NO][N][O]222
  • B𝐾=[NO][N][O]222
  • C𝐾=[NO][N][O]22222
  • D𝐾=[N][O][NO]222
  • E𝐾=[NO][N][O]22

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