I don't know how to approach this question? I need help

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1 Answer
Aug 10, 2018

sf("d".) "Rate" = k["SO"_2]["H"_2]

Explanation:

The question is asking for the order of the reaction about each reactant given data from the table supplies the following correlations:

  • Doubling ["SO"_2] while holding ["H"_2] constant doubles "Rate";
  • Holding ["H"_2] constant while doubling ["SO"_2] doubles "Rate".

Where ["SO"_2] and ["H"_2] represent the concentration of the two respective species, as your chemistry teacher has likely mentioned during classes.

Now back to the question: the key is to find an exponential relationship that properly satisfies all (or both, as in this question) arithmetic correlations the question has implied. For this particular case:

  • 1^color(navy)(1) xx 1^color(navy)(1) = 1
  • 2^color(navy)(1) xx 1^color(navy)(1) = 2
  • 2^color(navy)(1) xx 2^color(navy)(1) = 4

The exponent color(navy)(1) is typically omitted in many expressions. Thus the rate law for this reaction given these data would be

"Rate" = k["SO"_2]^color(navy)(1) ["H"_2]^color(navy)(1)

... where k the rate constant unique to this reaction and dependent on temperature.

As a side note, the cardinal number that corresponds to the exponent of a particular reactant identifies the order of that species in the reaction, for instance

  • A reaction is of "zero" order about a reactant with exponent 0 omitted (or in other words included as part of the constant k) in the rate law expression
  • A reaction is of "first" order about a reactant with exponent 1, as in this case for both reactants
  • A reaction is of "second" order about a reactant with exponent 2

Reactions of orders higher than two are rare given the unlikelihood for three microscopic particles to collide simultaneously.