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To study the effect of dilution, concentration of water and temperature on the rate of the chemical reaction between methanal (HCHO), sodium sulphite (Na2SO3) and sodium hydrogensulphite (NaHSO3).

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Introduction

Date: 21-1-2011 Objective: To study the effect of dilution, concentration of water and temperature on the rate of the chemical reaction between methanal (HCHO), sodium sulphite (Na2SO3) and sodium hydrogensulphite (NaHSO3). Chemicals: 0.3 M methanal about 100 cm3 solution B (containing 0.20 M NaHSO3 and 0.05 M Na2SO3) about 100 cm3 phenolphthalein indicator several dropping bottles shared Apparatus: Boiling tube x 6 100 cm3 beaker x 2 Glass rod x 1 250 cm3 beaker x 1 stop watch x 1 600 cm3 beaker x 1 10 cm3 measuring cylinder x 1 25cm3 measuring cylinder x 2 dropper x 3 white tile x 1 thermometer (-10? to 110?) x 1 Procedures: A. Effect of Dilution 1. According to the following table, distilled water was measured using a clean 10.0 cm3 measuring cylinder. each volume of water was poured into a clean and dry boiling tube. Volume of water (cm3) 0 2.5 5.0 7.5 10.0 12.5 15.0 The experiment was started with 0 cm3 of water in the clean and dry boiling tube. 2. 5.0 cm3 of 0.3 M methanal was measured using another clean 10.0 cm3 measuring cylinder and was poured into the first boiling tube. 3. 2 drops of phenolphthalein were added into the boiling tube. 4. ...read more.

Middle

C. Effect of Temperature 1. 400cm3 of hot water was poured into a 600 cm3 beaker 2. Keep the water bath at approximately 45?. 3. 10.0 cm3 of 0.3 M methanal and 20.0 cm3 of distilled water was measured using clean 10.0 cm3 measuring cylinders respectively and was poured into a clean and dry boiling tube. 4. 2 drops of phenolphthalein indicator were added into the boiling tube. 5. 10.0 cm3 of solution X was measured using a clean and dry 10.0 cm3 measuring cylinder and was poured into another clean and dry boiling tube. 6. The 2 boiling tubes were placed into the water bath for several minutes until the water, methanal and solution X in the boiling tubes were of the same temperature and were nearly equal to 45 ?. 7. The solution X was poured into the boiling tube containing methanal and water. 8. The stop watch was started immediately. 9. The reaction mixture was stirred quickly with a thermometer. 10. The time taken for the pink colour to appear was recorded in Table 3. 11. The highest temperature of the reaction mixture attained was also recorded in Table 3. ...read more.

Conclusion

Based on the graph plotted in part B, state the effect of the concentration of methanal on the rate of reaction between methanal, sodium sulphite and sodium hydrogensulphite. The larger the initial volume (higher concentration) of methanal in the reaction mixture, the shorter the time for the appearance of pink colour. The concentration of methanal and the rate of reaction between methanal, sodium sulphite and sodium hydrogensulphite are inversely related (inversely proportional)to each other. 4. Based on the graph plotted in part C, state the effect of temperature on the rate of the reaction between methanal, sodium sulphite and sodium hydrogensulphite. The higher temperature, the shorter the time for the appearance of pink colour The time for the appearance of pink colour decreased with the highest temperature of the reaction mixture attained in an exponential manner. Conclusion According to the experiments, the rate of the chemical reaction between methanal (HCHO), sodium sulphite (Na2SO3) and sodium hydrogensulphite (NaHSO3) increases with the decrease in volume of water used or the increase in concentration of methanal or the increase in temperature. Reference http://hk.knowledge.yahoo.com/question/question?qid=7006100204912 http://en.wikipedia.org/wiki/Chemical_clock http://en.wikipedia.org/wiki/Formaldehyde http://hk.search.yahoo.com/search/kp;_ylt=A8tU3w7p26ZMI3gADEDaygt.?p=word%E6%89%93%E5%88%86%E7%B7%9A&fr2=sb-top http://hk.knowledge.yahoo.com/question/question?qid=7008110601656 http://wyc.hkcampus.net/~wyc-lab1/Experiment/Form6_exp_1-19.pdf http://wblrd.sk.ca/~chem30_dev/2_kinetics/labs/clock_rxn_notes.pdf F.6 Chemistry Notes Section V by Ms Sin W L The End ?? ?? ?? ?? F.6 Chemistry/TAS 10/P.1(6) ...read more.

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