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CHEMISTRY, M5 2023 HSC 31

Copper() ions form a complex with lactic acid , as shown in the equation.

This complex can be detected by measuring its absorbance at 730 nm. A series of solutions containing known concentrations of were prepared, and their absorbances measured.
 

0.000 0.00
0.010 0.13
0.020 0.28
0.030 0.43
0.040 0.57
0.050 0.72
 
Two solutions containing were mixed. The initial concentrations of each in the resulting solution are shown in the table.
 
0.056
0.111

 
When the solution reached equilibrium, its absorbance at 730 nm was 0.66.

You may assume that under the conditions of this experiment, the only species present in the solution are those present in the equation above, and that is the only species that absorbs at 730 nm.

With the support of a line graph, calculate the equilibrium constant for the reaction.   (7 marks)
 

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CHEMISTRY, M5 EQ-Bank 24

When a sample of solid silver chloride is added to a mol L−1 sodium chloride solution, only some of the silver chloride dissolves.

Calculate the equilibrium concentration of silver ions in the resulting solution, given that the of silver chloride is .   (3 marks)

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CHEMISTRY, M5 2019 HSC 31

The following reaction occurs in an aqueous solution.

   

A solution containing a mixture of and ions is prepared. The initial concentration of each ion is 0.100 mol L ¯1 and there are no other ions present.

Calculate the concentration of ions once the system has reached equilibrium.   (4 marks)

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Since is small 

 
 
 
 
   

 

CHEMISTRY, M5 2020 HSC 35

In aqueous solution, iodide ions react rapidly with iodine to form triiodide ions , making the equilibrium system shown in the chemical equation:

The following relationships can be derived from the reaction mechanism:

where 'initial' designates the initial concentration and 'eq' designates the equilibrium concentration.

The absorbance of the solution in the UV-Vis spectrum is given by:

Determine the value of the equilibrium constant, given that    at equilibrium and  .  (4 marks)

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Mean mark 55%.