The reaction is third order
overall, is second
order in NO concentration and is first
order in H2 concentration. Observe
once again that the simple answer that you might expect from looking
at the coefficients of NO and H2 in the
balanced equation does not correspond with the experimental
The reaction of chlorine with chloroform to yield carbon tetrachloride
and hydrogen chloride is
and the observed rate
expression for production of HCl is
What is the overall order of reaction, and
what is the order with respect to each reactant?
The reaction is first order in chloroform concentration, half order
in chlorine concentration, and one-and-a-half order overall. Note
that there is no reason that the order cannot be fractional in one
or more concentrations.
that the coefficients in the balanced equation and in the rate law
generally do not agree is that the actual chemical reaction
mechanism usually is not a simultaneous collision of as many molecules
as the coefficients indicate. Instead, the overall mechanism is built
up from a series of smaller steps.