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Lesson Worksheet: Degree of Dissociation Chemistry

In this worksheet, we will practice defining and calculating the degree of dissociation of a weak acid and using it to derive Ostwald’s law of dilution.


Which of the following statements best describes the degree of dissociation of an acid?

  • AThe probability that the acid will dissociate in an aqueous solution
  • BThe fraction of reactant molecules that dissociate at equilibrium
  • CThe total number of hydrogen atoms that can dissociate from a molecule
  • DThe concentration of the acid at equilibrium
  • EThe fraction of ionic species produced at equilibrium


A weak acid with a dissociation constant of 1.54×10 mol/L is found to be 1.26% dissociated. What is the concentration of [H]+ ions? Give your answer to 2 decimal places.

  • A1.94×10 mol/L
  • B8.45×10 mol/L
  • C9.70×10 mol/L
  • D1.22×10 mol/L
  • E1.88×10 mol/L


A 0.3 M solution of benzoic acid was found to be 1.47% dissociated. What is the value of 𝐾, to 2 decimal places, for this acid? Assume 1𝛼1.

  • A6.48×10 mol/L
  • B4.41×10 mol/L
  • C4.26×10 mol/L
  • D1.32×10 mol/L
  • E4.9×10 mol/L


To 1 decimal place, what is the degree of dissociation for a 0.25 M solution of phenol at 25C? The dissociation constant 𝐾 is 1.6×10 M.

  • A2.5×10
  • B1.4×10
  • C4.0×10
  • D4.0×10
  • E6.4×10


The equations below show a form of Ostwald’s law of dilution along with its simplified form:


Which of the following approximation results in the simplified form of the equation?

  • AWhen 𝛼 is very small, (1𝛼) can be approximated to be equal to 1.
  • BFor strong acids, 𝛼 approaches 1, and so (1𝛼) can be approximated to be equal to 0.
  • CWhen 𝛼 is very large, (1𝛼) can be approximated to be equal to 0.
  • DWhen v is very large, (1𝛼) can be ignored in the equation.


Which of the following factors would increase the degree of dissociation of a weak acid?

  • AIncreasing dilution
  • BDecreasing volume
  • CDecreasing dilution
  • DIncreasing acid concentration


According to Ostwald’s law of dilution, which of the following is the correct relationship between the dissociation constant (𝐾) and the degree of dissociation (𝛼)? Assume that 1𝛼1.

  • A𝐾=𝐶𝛼
  • B𝐾=𝛼𝐶
  • C𝐾=𝛼𝐶
  • D𝐾=𝛼𝐶
  • E𝐾=𝛼𝐶


Formic acid (HCOOH) is a common weak acid that is found primarily in wood ants. If 0.02 mol of HCOOH is dissolved into 1 L of water at 25C, what is [HO]3+ if 𝐾 of HCOOH is 1.8×10? Give your answer to 1 decimal place.

  • A2.7×10 mol/L
  • B9.5×10 mol/L
  • C1.9×10 mol/L
  • D3.6×10 mol/L
  • E1.1×10 mol/L


You are given 5 acidic solutions in a lab experiment, and each acid exhibits a different degree of dissociation, as seen in the table.

Degree of Dissociation2.8%5.9%11.2%6.7%7.9%

Which acid has better electrical conductivity? Assume that their concentration is the same and that room temperature is maintained.

  • AHY
  • BHU
  • CHW
  • DHZ
  • EHX


Which of the following is true about weak acids?

  • ATheir degree of ionisation is very high.
  • BTheir degree of ionisation is very small.
  • CThey are completely ionised in water.
  • DTheir degree of ionisation is moderate.

This lesson includes 17 additional questions and 25 additional question variations for subscribers.

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