Level 2 AS91162

Carry out procedures to identify ions present in solution (2.2)

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This annotated exemplar is intended for teacher use only. The student work shown does not always represent a complete sample of what is required. Selected extracts are used, focused on the grade boundaries, in order to assist assessors to make judgements at the national standard.

Low Excellence

Commentary
Student work extract

Student 1 (PDF, 81KB)

For Excellence, the student needs to carry out procedures to comprehensively justify the identification of ions present in solution.

This involves:

  • interpreting observations by recognising the formation of complex ions
  • writing balanced equations for these reactions

This student has made links between the observations and the reactions for the ion identified (1), has justified the identification of the ion by showing how the identification process eliminates or include ions for most of the steps (2), and has correctly balanced precipitation and complex ion equations (3).

For a more secure Excellence, the student could show their justification for each step in the identification of the ion by showing which ions are eliminated or included for each step of the identification process.

High Merit

Commentary
Student work extract

Student 2 (PDF, 80KB)

For Merit, the student needs to carry out procedures to justify the identification of ions present in solution.

This involves writing balanced equations for all the reactions where precipitates are formed.

This student has identified all of the precipitates for the observations (1), correctly balanced all of the precipitation equations (2), has made links between the observations to the reactions (3), and has shown how the identification process used eliminates or includes ions for some of the key steps (4).

To reach Excellence, the student could complete the complex ion equation correctly, and link each step in the identification process to the ions eliminated or included.

Low Merit

Commentary
Student work extract

Student 3 (PDF, 79KB)

For Merit, the student needs to carry out procedures to justify the identification of ions present in solution.

This involves writing balanced equations for all the reactions where precipitates are formed.

This student has identified all of the precipitates for the observations (1), correctly balanced most of the precipitation equations (2), and made some links between the observations and the reactions (3).

For a more secure Merit, the student could complete all of the precipitation reactions correctly, and fully link the observations to the precipitation reaction involved.

High Achieved

Commentary
Student work extract

Student 4 (PDF, 77KB)

For Achieved, the student needs to carry out procedures to identify ions present in solution.

This involves:

  • collecting primary data
  • using these observations to identify ions in solution using a procedure provided.

This student has stated the observations for each step of the identification process (1) and correctly identified all of the ions (2) and the precipitates formed (3) (with either words or formulae).

To reach Merit, the student could make links between the observations and the reactions for the steps in the identification process, and correctly complete balanced equations for the precipitation reactions.

Low Achieved

Commentary
Student work extract

Student 5 (PDF, 76KB)

For Achieved, the student needs to carry out procedures to identify ions present in solution.

This involves:

  • collecting primary data
  • using these observations to identify ions in solution using a procedure provided.

This student has correctly identified the ions (1), recorded the observations for each step of the process (2), and identified most of the precipitates formed (3) (with either words or formulae).

For a more secure Achieved, the student could identify all of the precipitates formed for each step in the process, for example by including aluminium hydroxide for the addition of NH3.

High Not Achieved

Commentary
Student work extract

Student 6 (PDF, 76KB)

For Achieved, the student needs to carry out procedures to identify ions present in solution.

This involves:

  • collecting primary data
  • using these observations to identify ions in solution using a procedure provided.

This student has identified all of the ions (1) and provided the correct observations for each step of the process (2).

To reach Achieved, the student could identify the precipitates formed, for example aluminium hydroxide and barium sulfate.

 
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