Write rate law expressions?

2NOCl(g) --> 2NO(g) + Cl2(g)
S2O3^2-(aq) + H^+(aq) --> HSO3^-(aq) + S(s)

(Sulfur initially forms a colloid solution so it can be treated as aqueous.)

(1) Write the rate law expression for the above reactions, assuming these are elementary.

(2) If total pressure in the system is doubled, how will it affect the rate of the reaction in each case?

1. So since these are elementary, I think they're written just like this:

rate = k[NOCl]
rate = k[S2O3^2-][H^+]

2. For gaseous reactions, when pressure increases the rate of reaction increases, so the first one would have an increased rate of reaction.

I'm not really sure about the second one though. Tell me if I'm thinking about this the right way: since the reaction is aqueous and nothing is gaseous, then pressure will not affect the rate of reaction

?

Write rate law expressions?

2NOCl(g) --> 2NO(g) + Cl2(g)
rate=k[NOCl]^2 based on the Law of Mass Action. That is not necessarily the actual rate law, which must be determined by experiment.
The effect of pressure depends on how the pressure is increased. IF it is increased by reducing the volume, the side with the smallest number of GAS molecules is favored. In this case the left side will be favored (only 2 gas molecules versus 3 on the right side).
S2O3^2-(aq) + H^+(aq) --> HSO3^-(aq) + S(s)
r=k[2O3^2-][H^+] as you indicated but not necessarily the actual rate law.

You are correct in writing the rate law expressions for the given reactions assuming they are elementary. The rate law expression for the first reaction, 2NOCl(g) --> 2NO(g) + Cl2(g), is rate = k[NOCl]. This indicates that the rate of the reaction is directly proportional to the concentration of NOCl raised to the power of 1.

Similarly, for the second reaction, S2O3^2-(aq) + H^+(aq) --> HSO3^-(aq) + S(s), the rate law expression is rate = k[S2O3^2-][H^+]. This indicates that the rate of the reaction is directly proportional to the concentrations of S2O3^2- and H^+ raised to the powers of 1.

Now, let's consider how the rate of reaction will be affected by doubling the total pressure in the system for each case.

In the first reaction, where all species are in the gaseous phase, doubling the total pressure will increase the concentration of each gaseous reactant. According to the rate law expression rate = k[NOCl], an increase in the concentration of NOCl will result in an increased rate of reaction. Therefore, doubling the total pressure will increase the rate of the first reaction.

In the second reaction, where all species are in the aqueous phase, the rate law expression rate = k[S2O3^2-][H^+] indicates that the rate of the reaction depends on the concentrations of S2O3^2- and H^+. Since pressure does not directly affect the concentration of species in the aqueous phase, doubling the total pressure will have no effect on the rate of the second reaction.

To summarize, doubling the total pressure will increase the rate of the first reaction involving gaseous species, but will have no effect on the rate of the second reaction involving aqueous species.