Cash4Coursework has been rebranded ‘FreeCoursework.info’ - Visit us to download coursework for free and to earn money from your old coursework!
View this page at Freecoursework.info
The determining of a rate equation from the reaction of sodium thiosulphate with hydrochloric acid - page 5
Keywords: The determining of a rate equation from the reaction of sodium thiosulphate with hydrochloric acid
By Carlitob10 on 04/11/2006 11:57:07
Level: A Level (Year 13)
Page Number: 5 of 8 pages: 1 2 3 4 5 6 7 8the reactants.
Rate: R = k [A]2
These three behaviors are illustrated in the following graph:
• For a zero-order reaction (red line), the rate of reaction is constant as the reaction progresses.
• For a first-order reaction (green line), the rate of reaction is directly proportional to the concentration. As the reactant is consumed during the reaction, the concentration drops and so does the rate of reaction.
• For a second-order reaction (blue line), the rate of reaction increases with the square of the concentration, producing an upward curving line in the rate-concentration plot. For this type of reaction, the rate of reaction decreases rapidly (faster than linearly) as the concentration of the reactant decreases.
Analysis
Table of results for the variation of HCl with 20 cm3 of 0.4M Na2S2O3 as constant:
Concentration of HCl (mol dm-3) Time 1 (s) Time 2 (s) Time 3 (s) Average Time (s) Rate of reaction 1/time (s-1)
2 12.98 13.94 13.06 13.33 0.08
1.6 15.44 15.59 15.22 15.42 0.06
1.2 16.84 17.1 18.02 17.32 0.06
0.8 20.14 20.22 19.96 20.11 0.05
0.4 22.29 22.94 23.14 22.79 0.04
0.2 27.31 28.06 28.13 27.83 0.04
0.1 44.63 45.82 46.32 45.59 0.02
Table of results for the variation of Na2S2O3 with 5.0 cm3 of 2.0M HCl as constant:
Concentration of thiosulphate (mol dm-3) Time 1 (s) Time 2 (s) Time 3 (s) Average Time (s) Rate of reaction 1/time (s-1)
0.4 16.13 15.22 15.75 15.70 0.06
0.35 17.31 17.28 18.1 17.56 0.06
0.3 18.27 18.02 18 18.10 0.06
0.25 19.33 19.69 20.03 19.68 0.05
0.2 22.03 21.92 21.84 21.93 0.05
0.15 28.51 28.94 29.44 28.96 0.03
0.1 33.48 33.66 33.87 33.67 0.03
Determining the rate equation:
The equation for the reaction whose rate we have been measuring is as follows:
S2O32- (aq) + 2H+ (aq) 2NaCl (aq) + SO2 (g) + S (s) + H2O (l)
The rate equation states the relationship between the rate of reaction and the concentration of each reactant. The dependence of the rate of reaction on the concentration of a reactant can be expressed mathematically in the form:
Rate [reactant]n
which gives the rate equation as:
Rate = k [reactant]n
where k is the rate constant and n is the order of the reaction with respect to the given reactant. The order of reaction is the power to which the concentration of the reactant is raised in the experimentally determined rate equation. The definition of order of reaction states that the rate equation must be determined by experiment, and has nothing to do with the stoichiometric equation. From my experimentally obtained results, I will work out the orders of reaction with respect to each reactant, and hence write the overall rate equation.
Let us begin by looking at table
Last 5 comments…
There have been no comments posted for this article, but you need to register if you want to be the first!