Science 30 January 1999 Grade 12 Diploma Examination
Science 30 January 1999 Grade 12 Diploma Examination Science 30 January 1999 Grade 12 Diploma Examination
24. The use of pesticides may pose a problem because pesticides sometimesA. do not biodegrade easilyB. decrease the global rate of photosynthesisC. increase the biochemical oxygen demand of waterD. increase the amount of ultraviolet light entering the atmosphere25. The pollutants that contribute most to acid deposition areA. CO (g) and NO 2(g)B. SO 2(g) and NO 2(g)C. CO (g) and SO 2(g)D. NO 2(g) and O 3(g)Numerical Response05. The pH of a sample of lake water is 3.42. The hydronium ion concentration [H 3 O + (aq) ]of the sample is __________. 10 –4 mol/L.(Record your answer to two digits in the numerical-response section on the answer sheet.)26. When a few drops of indicator bromothymol blue are added to a lake water samplewith a pH of 3.42, the colour of the sample isA. redB. greenC. orangeD. yellow27. Acid deposition may change the pH of a lake. In addition, as acidified water passesthrough soil and into the lake, it may alsoA. increase the temperature of the lakeB. reduce the dissolved oxygen content of the lakeC. increase the decay rate of organic matter in the lakeD. increase the concentration of dissolved metal ions in the lake14
Short Answer – 5%In a lab, you are asked to determine the concentration of a strong acid by titrating it with astrong base. Outline the steps you would take to carry out the titration using the followingequipment and supplies. Include set-up and clean-up procedures.buretfunnelpipette and bulb (or pump)distilled waterErlenmeyer flasksmicropipettegraduated cylinderdrop plateindicator (bromothymol blue) strong base (NaOH (aq) )strong acid (HCl (aq) )Note: You may choose to not use all of the equipment to carry out the procedure.15
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24. The use of pesticides may pose a problem because pesticides sometimesA. do not biodegrade easilyB. decrease the global rate of photosynthesisC. increase the biochemical oxygen demand of waterD. increase the amount of ultraviolet light entering the atmosphere25. The pollutants that contribute most to acid deposition areA. CO (g) and NO 2(g)B. SO 2(g) and NO 2(g)C. CO (g) and SO 2(g)D. NO 2(g) and O 3(g)Numerical Response05. The pH of a sample of lake water is 3.42. The hydronium ion concentration [H 3 O + (aq) ]of the sample is __________. 10 –4 mol/L.(Record your answer to two digits in the numerical-response section on the answer sheet.)26. When a few drops of indicator bromothymol blue are added to a lake water samplewith a pH of 3.42, the colour of the sample isA. redB. greenC. orangeD. yellow27. Acid deposition may change the pH of a lake. In addition, as acidified water passesthrough soil and into the lake, it may alsoA. increase the temperature of the lakeB. reduce the dissolved oxygen content of the lakeC. increase the decay rate of organic matter in the lakeD. increase the concentration of dissolved metal ions in the lake14
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