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Worksheet: Reaction Rates

Q1:

Ammonia decomposes into hydrogen and nitrogen at high temperature. The rate of decomposition of ammonia is found to be 2 . 1 0 × 1 0 6 M/s.

Write a balanced chemical equation for this reaction.

  • A 2 N H ( ) 3 N ( ) + 3 H ( ) 3 2 2 g g g
  • B N H ( ) N ( ) + 3 H ( ) 3 g g g
  • C 3 N H ( ) 3 N ( ) + 2 H ( ) 3 2 g g g
  • D 2 N H ( ) N ( ) + 3 H ( ) 3 2 2 g g g
  • E 2 N H ( ) N ( ) + 6 H ( ) 3 2 g g g

What is the rate of formation of nitrogen?

  • A 1 . 0 5 × 1 0 6 M/s
  • B 4 . 2 0 × 1 0 6 M/s
  • C 3 . 1 5 × 1 0 6 M/s
  • D 2 . 1 0 × 1 0 6 M/s
  • E 2 . 8 0 × 1 0 6 M/s

What is the rate of formation of hydrogen?

  • A 2 . 8 0 × 1 0 6 M/s
  • B 1 . 0 5 × 1 0 6 M/s
  • C 3 . 1 5 × 1 0 6 M/s
  • D 2 . 1 0 × 1 0 6 M/s
  • E 4 . 2 0 × 1 0 6 M/s

Q2:

A reaction begins at a time 𝑡 = 0 and is monitored over a period of time, 𝑇 , by measuring the reactant concentration, 𝐶 , at fixed time intervals. How is the instantaneous rate at 𝑇 calculated from a graph of 𝐶 against 𝑡 ?

  • ABy calculating the total area under the graph between 𝑡 = 0 and 𝑡 = 𝑇
  • BBy fitting a polynomial function to the curve and evaluating the derivative of this function at 𝑡 = 𝑇
  • CBy dividing the change in 𝐶 between 𝑡 = 0 and 𝑡 = 𝑇 by 𝑇
  • DBy calculating the gradient of the tangent at 𝑡 = 𝑇
  • EBy calculating the gradient of the tangent at 𝑡 = 𝑇 2

Q3:

Dinitrogen pentoxide decomposes in chloroform to form nitrogen dioxide and oxygen: The decomposition is a first-order reaction with a rate constant of 6 . 2 0 × 1 0 4 min−1 at 4 5 C . Calculate the rate of reaction in M/s when [ N O 2 5 ] = 0.400 M.

  • A 6 . 8 9 × 1 0 8 M/s
  • B 1 . 0 3 × 1 0 5 M/s
  • C 2 . 4 8 × 1 0 4 M/s
  • D 4 . 1 3 × 1 0 6 M/s
  • E 2 . 5 8 × 1 0 5 M/s

Q4:

A reaction begins at a time 𝑡 = 0 and is monitored over a period of time, 𝑇 , by measuring the reactant concentration, 𝐶 , at fixed time intervals. How is the average rate of reaction for this time period calculated from a graph of 𝐶 against 𝑡 ?

  • ABy calculating the total area under the graph between 𝑡 = 0 and 𝑡 = 𝑇
  • BBy fitting a polynomial function to the curve and evaluating the derivative of this function at 𝑡 = 𝑇
  • CBy calculating the gradient of the tangent at 𝑡 = 𝑇
  • DBy dividing the change in 𝐶 between 𝑡 = 0 and 𝑡 = 𝑇 by 𝑇
  • EBy calculating the gradient of the tangent at 𝑡 = 𝑇 2

Q5:

Aqueous hydrogen peroxide ( H O 2 2 ) decomposes into oxygen and water. The rate of decomposition of hydrogen peroxide is found to be 3 . 2 0 × 1 0 2 M/h.

Write a balanced chemical equation for this reaction.

  • A 2 H O ( ) 2 H O ( ) + O ( ) 2 2 2 a q l g
  • B H O ( ) H O ( ) + O ( ) 2 2 2 a q l g
  • C 2 H O ( ) H O ( ) + O ( ) 2 2 2 2 a q l g
  • D 2 H O ( ) 2 H O ( ) + O ( ) 2 2 2 2 a q l g
  • E H O ( ) 2 H O ( ) + 2 O ( ) 2 2 2 2 a q l g

What is the rate of formation of water?

  • A 3 . 2 0 × 1 0 2 M/h
  • B 2 . 1 3 × 1 0 2 M/h
  • C 6 . 4 0 × 1 0 2 M/h
  • D 1 . 6 0 × 1 0 2 M/h
  • E 4 . 8 0 × 1 0 2 M/h

What is the rate of formation of oxygen?

  • A 4 . 8 0 × 1 0 2 M/h
  • B 3 . 2 0 × 1 0 2 M/h
  • C 1 . 6 0 × 1 0 2 M/h
  • D 6 . 4 0 × 1 0 2 M/h
  • E 2 . 1 3 × 1 0 2 M/h

Q6:

Consider the equilibrium for the ionization of the H S O 4 ion, a weak acid used in some household cleaners: For a mixture of N a H S O 4 and N a S O 2 4 at equilibrium, the following are the concentrations:

[ H O ] 3 + = 0.027 M,

[ H S O ] 4 = 0.29 M,

[ S O ] 4 2 = 0.13 M.

What is the equilibrium constant for this reaction under these conditions?

  • A 8 . 2 × 1 0 7 M/s
  • B 2 . 2 × 1 0 6 M/s
  • C 2 . 2 × 1 0 7 M/s
  • D 1 . 9 × 1 0 6 M/s
  • E 1 . 0 × 1 0 6 M/s