Rates of Reaction

Measuring the Rate of a Reaction.

2) The reaction between sodium thiosulfate solution
and dilute hydrochloric acid.

HCl + sodium thiosulfate arrow sodium chloride + sulfur dioxide + sulfur + water.
2HCl(aq)  +  Na2S2O3(aq)  arrow        2NaCl(aq)     +     SO2(g)   +      S(s)  +  H2O(l)

The solid sulfur (S(s)) formed in this reaction
makes the colourless solution go cloudy.

The reaction is usually carried out in a flask placed on a
piece of white paper. The white paper has a black cross on it.
At the beginning of the reaction, the cross can easily be
seen through the solution in the flask. As the flask
becomes more and more cloudy, the cross gets harder to see.

You can measure the time from the start of the reaction
until the cross can no longer be seen.
This is a way of measuring the rate of formation of sulfur.

The reaction between magnesium and dilute acid
can be followed in a similar way
noting the time taken for the magnesium to disappear.

See also increasing the concentration of a reaction.

back     Links     Catalysts and Energy     Enzymes     Revision Questions     next

gcsescience.com      The Periodic Table      Index      Reaction Rate Quiz      gcsescience.com

Home      GCSE Chemistry      GCSE Physics

Copyright © 2014 Dr. Colin France. All Rights Reserved.