Sample D –TEACHER INSTRUCTIONS I.B. CHEMISTRY : PRACTICAL
INVESTIGATION : INVESTIGATE THE RATE OF ELECTROPLATING A METAL D DCP CE
Goggles and Lab coats must be worn
Background Students had been taught ‘Electrochemistry’ as outlined in the IB Chemistry syllabus. Investigation Design an experiment that allows you to investigate a variable affecting the rate of electroplating. Your research question must be focussed and specific and must enable you to carry out your experiment safely and within the allocated time. Safety Show your research question to your teacher. Complete a safety hazard assessment before writing a full plan (a + b). Ensure your teacher approves this. Experiment If your plan is safe you will be allowed to complete your experiment, though you must give your teacher notice of any non-standard apparatus you will require, one lesson in advance of your experiment. Assessment Your teacher may take this opportunity to assess almost all of the skills, so work hard and remember to check the criteria.
STUDENT’S WORK Chemistry Practical Investigation: Investigate the Rate of Electroplating a Metal Research Question How does the current flowing through the system (0.20 A, 0.40 A, 0.60 A, 0.80 A 1.00 A) affect the rate of electroplating of a copper electrode when the volume (150cm3) and concentration of the copper sulphate electrolyte (1.00 moldm-3), temperature of the system, contact surface area of electrodes and duration of the experiment are kept constant? Independent Variable Current Flowing through the system. Dependent Variable Rate of Electroplating of a Copper Electrode Controlled Variables Volume of Electrolyte used Concentration and Purity of Electrolyte used Temperature of the system Contact surface area of Electrodes Duration of Experiment Apparatus 12V Power Supply, 2x 250cm3 Beaker, 1x 250cm3 Measuring Cylinder ( cm3), Wires, Crocodile Clips, Rheostat, Digital Multimeter ( 0.01A), Electronic Milligram Balance ( 0.001g), Hair Dryer, Thermometer, Scissors, Ruler, Stopcock ( 1 s). Materials 12 x Copper Strips (8 cm x 2 cm), 900 cm3 Copper Sulphate Solution (1.00M Water. Procedure
Before the experiment is carried out, quickly construct a ‘test’ circuit to check that all the apparatus is in working order and that it actually produces a measurable current. For this part of the investigation it is not important to thoroughly control all the variables – it’s purpose is to check that my ideas are correct. 2
1. 150cm3 of distilled water is measured out using a 250cm3 measuring cylinder and is poured into a 250cm3 beaker. 2. A copper strip is folded in half, creating a thick (4cm x 2cm) piece. It is unfolded and is dipped in the water so that the fold mark is in line with the water level. At this height, the copper strip is folded down the mouth of the beaker so that it stays still. 3. The copper strip is removed. The length between the end and the new fold mark is recorded and all the other copper and strips are marked lightly at this length with a pencil. 4. When used as an electrode, the metal strips have to be folded down the mouth of the beaker at this new mark to ensure that the contact surface area of the strips remain constant. 5. The 250cm3 measuring cylinder and 250cm3 beaker are cleaned and dried. 6. The apparatus is set up as shown in the diagram above. 7. The crocodile clips are attached to the copper electrodes of the calibration apparatus and the power supply is set at 6V and is turned on. The rheostat is adjusted until the multimeter shows a reading of approximately (0.20A). 8. The power supply is turned off and the crocodile clips are removed from the calibration apparatus. 9. The negative cathode of the experimental apparatus is removed, weighed on an electronic milligram balance and its initial mass is recorded. It is then replaced in its original position. 10. 150cm3 of 1.00 copper sulphate solution is measured out using a 250cm3...
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