The reaction between sodium thiosulphate and hydrochloric acid:Looking at the graph the order of reaction established is 1st order

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Interpretation

Investigation 1:the effect of concentration changes

To summaries the results of the investigations the rate of reaction is used in the form of a rate equation. A rate equation shows how changes in the concentrations of reactants  affect the rate of a reaction.

An example of a general reaction for which x mol A react with y mol B to form products:

xA + yB products

The rate equation is expressed in this form:

Rate = k[A]n [B]m

Where [A] and [B] represents the concentrations of the reactants in moles per litre. The powers n and m are the reaction orders. Therefore the reaction above is order n with respect to A and order m with respect to B the overall order is (n+m).The rate constant, k, is only constant for a particular temperature.

The reaction between sodium thiosulphate and hydrochloric acid:

Looking at the graph the order of reaction established is 1st order.

Na2S2O3(aq) + 2HCl(aq) S(s) + SO2(g) + H2O(l) + 2NaCl(aq)

Has a rate equation of the type:

reaction rate = k [Na2S2O3]1[HCl]1 = k [Na2S2O3] [HCl]

The reaction is first order with respect to Na2S2O3 and is first order with respect to HCl. The overall order is given by the sum of the indices of each component of the rate equation. In this case, the overall order is given by (1 + 1) =2 order.

The effect of sodium thiosulphate

If the concentration of any reactant in a solution is increased, the rate of reaction is increased.

Increasing the concentration, increases the probability of a collision between reactant particles because there are more of them in the same volume and so increases the chance of a collision, forming products.

From the results obtained in figure 2.1, illustrates that change in concentration of sodium thiosulphate has an effect on the rate of reaction between hydrochloric acid, the rate of reaction is slightly slow, when kept at a constant volume and concentration.

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The effect of hydrochloric acid

The results in figure 2.2 shows that change in concentration of hydrochloric acid, has no effect on the rate of reaction between sodium thiosulphate when kept at a constant volume and concentration . The rate of reaction is higher in in this reaction as the concentration increases.

Investigation 2: The effect of temperature changes

The collision theory:

The collision theory is stated that reactions occur when molecules collide with a certain minimum kinetic energy. The more frequent these collisions, the faster the reaction.

This energy is ...

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