The question is "the reaction CO + SO3 <=> CO2 + SO2 has two possible mechanisms. If the rate law for this reaction is rate=k[SO3] which mechanisms is correct? which step in THAT mechanisms is the slow step?

and the mechanisms are:
mechanism 1
CO + @ -> CO@
SO3 + CO@ -> CO2 + SO2@
SO2@ -> SO2 + @

Mechanism 2
SO3 -> SO2 + O
CO + O -> CO2

and for the answers I said the first one is the correct and the second one is the slow step. Is this right?

If the reaction below proceeds with a 96.8% yield, how many kilograms of CaSO4 are formed when 5.91 kg SO2 reacts with an excess of CaCO3 and O2?

2 CaCO3(s) + 2 SO2(g) + O2(g) → 2 CaSO4(g) + 2 CO2(g)

To determine the correct mechanism and the slow step, we need to analyze the proposed mechanisms and compare them to the given rate law. Let's break it down step by step:

Mechanism 1:
CO + @ -> CO@
SO3 + CO@ -> CO2 + SO2@
SO2@ -> SO2 + @

Mechanism 2:
SO3 -> SO2 + O
CO + O -> CO2

Now let's compare the rate law (rate = k[SO3]) to the proposed mechanisms. According to the rate law, the rate of the reaction depends only on the concentration of SO3. Looking at Mechanism 1, we can see that the only step involving SO3 is the second step, which is consistent with the rate law. Therefore, Mechanism 1 is correct.

Next, let's determine the slow step. The slow step is typically the step with the highest activation energy and determines the overall rate of the reaction. In Mechanism 1, we can see that the second step involves the reactants CO@ and SO3. If this step is slow, it would mean that it has a higher activation energy compared to the other steps. Therefore, the second step in Mechanism 1 is the slow step.

In summary:
- Mechanism 1 is correct because it is consistent with the given rate law.
- The slow step in Mechanism 1 is the second step, "SO3 + CO@ -> CO2 + SO2@".

So your answer is correct!