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To study the factors which affect the rate of the methanol clock reaction.

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Introduction

Chemistry lab report 1) Experiment No.: 9 2) Objective: To study the factors which affect the rate of the methanol clock reaction. 3) Date: 17th December, 2010 4) Theory: The experiment consists of 2 parts. In both parts, the following reaction between methanol and hydrogensulphate(IV) ion occurs: HCHO + HSO3- --> CH2OHSO3- hydrogensulphate(IV) is consumed in the reaction. When its concentration drops to a certain level, the pH rises sharply, and pink color will be observed as phenolphthalein indicator was used. In part (A), different known amount of water was mixed with different known amount of methanol with a little phenolphthalein added. Then a known amount of sodium hydrogensulphate(IV) and sodium sulphate(IV) solution was added to the mixture. In part (B), a known amount of water was mixed with a known amount of methanol with a little phenolphthalein added. Then a known amount of sodium hydrogensulphate(IV) and sodium sulphate(IV) solution was added to the mixture at different temperature. ...read more.

Middle

of methanol: 0.3M Conc. of NaHSO3: 0.2M Conc. of Na2SO3 : 0.05M 8) Calculation for discussion A Part (A): 1 2 3 4 5 Concentration of methanol mol/dm3 0.075 0.1125 0.15 0.1875 0.225 In[Concentration of methanol] -2.59 -2.19 -1.90 -1.67 -1.49 [Concentration of methanol]-1 mol-1/dm-3 13.33 8.89 6.67 5.33 4.44 * Using integrated rate equations: [A] = -k t + [A]0 (1) In[A] = -k t + In[A]0 (2) [A]-1 = k t + [A]0-1 (3) Where [A] is methanol. * Using equation (1), plotting a graph of [A] against time t. If negative slope with initial conc. of [A] is shown, it is a zero order reaction. * Using equation (2), plotting a graph of In[A] against time t. If negative slope with In[initial conc. of [A]] together with positive y-intercept is shown, it is a first order reaction. * Using equation (3), plotting a graph of [A]-1 against time t. If positive slope with [initial conc. ...read more.

Conclusion

= (8.314)x(-11111) = 92.378 kJ mol-1 Activation energy of the Formaldehyde Clock Reaction is 92.378 kJ mol-1 9) Remarks: (a) In part (A), the volume of water increase when the volume of methanol decrease, and the volume of NaHSO3 and Na2SO3 was kept constant to ensure that the concentration of NaHSO3 and Na2SO3 will be the same among the five attempts as the total volume of water and methanol will still be 20cm3 It was done so because when doing experiment to determine how factors affecting the rate of a chemical reaction, only one factor can be a variable each time while others are kept constant. (b) In part (B), an increase in temperature will increase the rate of reaction because as a reaction occurs when the reactant molecules process enough energy and collide together, so when the temperature of reactants increase, the molecules will process more energy and they will also move more vigorously, thus increases the chance for molecule collision. Then the rate of reaction will be increase as a result. ~End of report~ ?? ?? ?? ?? ...read more.

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