Rates of Reaction
Measuring the Rate of a Reaction.
2) The reaction between sodium thiosulfate
and dilute hydrochloric acid.
HCl + sodium thiosulfate sodium chloride + sulfur
dioxide + sulfur + water.
HCl(aq) + Na2S2O3(aq) NaCl(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
can be followed in a similar way
noting the time taken for the magnesium to disappear.
See also increasing the concentration of a reaction.
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