Science 30 January 1999 Grade 12 Diploma Examination

Scoring Guide – Short Answer January 1999 Diploma ExaminationScore4StandardofExcellence32AcceptableStandardScoring DescriptionsThe response reflects an accurate understanding of the titration procedure. Thesteps and equipment used are appropriate.The response reflects an adequate understanding of the titration procedure. Thesteps and equipment apply to the titration procedure.The response reflects a sketchy understanding of the titration procedure. The stepsand equipment generally apply to titration procedure.The response reflects a poor understanding of the titration procedure. The stepsand equipment do not apply to titration procedure.10 The response does not address any of the major points of the question at anappropriate level for a 30-level course.Sample Answer – Short AnswerRinse a buret with water, then with the strong base. Put some base in the buret and recordthe initial volume.Add an indicator (bromothymol blue) to 10 mL of acid.Carefully add the base to the acid until the indicator changes colour.Record the final volume on the buret and subtract the initial volume.Rinse the buret and other containers with water.