What is the rate equation of the reaction between sodium thiosulphate and hydrochloric acid?

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Introduction

What is the rate equation of the reaction between sodium thiosulphate and hydrochloric acid? Overview Sodium thiosulphate and hydrochloric acid react according to the stoichiometric equation: Na2S2O3 (aq) + 2HCl (aq) 2NaCl (aq) + H2O (l) + SO2 (aq) + S(s) The balanced equation, however, does not tell us how the reactants become products. A rate law or rate equation, however, can. The purpose of this experiment is to determine the rate equation for the reaction between sodium thiosulphate and hydrochloric acid by determining the order of reaction with respect to sodium thiosulphate and hydrochloric acid. The order of reaction for each reactant is, in this case, determined by varying the concentrations of each reactant in turn while keeping the others constant. Data Collection and Processing] Raw Data Table Trial One Volume of Na2S2O3 /cm3 Volume of water /cm3 Volume of HCl /cm3 Time /s 50 0 10 49.7 40 10 10 64.6 30 20 10 95.0 15 35 10 222.2 5 45 10 1165.6 We made a brand new batch of sodium thiosulphate for the second trial.

Middle

- Data Processing Overview- The first thing I will do is determine the concentration of sodium thiosulphate and hydrochloric acid at each corresponding volume. Then I will determine the average time taken for an X drawn on a piece of paper and placed under the Erlenmeyer flask to become obscured. Next I will determine the rate of each reactant at each given concentration for either reactant. Finally I will plot separate graphs of 1/time against the concentration of the reactant under consideration. Sample Calculation- Concentration of sodium thiosulphate in solution containing 50 cm3 of sodium thiosulphate: number of moles of Na2S2O3 used = C * V/1000 = 0.1 mol dm-3 * (50/1000 dm3) = 0.005 mol concentration of Na2S2O3 (mol dm-3) = n / V = 0.005 mol / 0.05 dm3 = 0.1 mol dm-3 Volume of Na2S2O3 /cm3 Concentration of Na2S2O3 /mol dm-3 50 0.1 40 0.08 30 0.06 15 0.03 5 0.01 The molarity of the hydrochloric acid is 1 mol.

Conclusion

- Rate expression given by rate = k[Na2S2O3][HCl]2. Limitations of Experimental Design Suggestions for Improvement We made a new batch of sodium thiosulphate for the second trial of altering the concentration of sodium thiosulphate in all volumes except for that of 15cm3 Estimate how much sodium thiosulphate you will need beforehand so that you're sure to have enough of the batch of sodium thiosulphate We used results from both other groups to get our two other trials for when we altered the [HCl] so whatever errors they made are also ours Make sure to allocate time better so that we can conduct all trials We varied the concentration of sodium thiosulphate one day and the concentration of HCl another. It's most likely the room temperature changed between those two days. Make sure to conduct both parts of the experiment on the same day, in the same room. We used a brand new bottle HCl acid for when we altered the concentration of HCl. Use the same bottle of HCl for both alterations of concentrations of each reactant.

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