Question

q.1 why liquid br2 reacts slowly as compared to vapours of bromine?
q2.the 3/4th order of first reaction is completed in 32 minutes. what is the t half of the reaction?
q3.if the first order reaction is 2 minutes.how long it will take [A] to reach
a)25%of its initial concentration
b)10%of its initial concentration?
q4.the first order is 20%complete in 10 minutes.calculate the time for completion of 75%of the reaction?
please provide me solutions of these question

Answer 1

1)I don't really know why.
2)The key to this problem is understanding the relationship between the half-lives. For a first order reaction, t(1/2) = ln(2)/k; note how concentration doesn't matter. What this essentially means is that each half-life for a first order reaction will take the same amount of time.

Since 1/4th of the original concentration of reactants is remaining, we have gone through 2 half-lives - the concentration has been cut in half, then cut in half again. Since the half-life for a first order reaction is concentration-independent (and thus both the first and second half lives must each be the same length), the half-life period is 32/2 or 16 minutes.

3) This website will help you a lot, this is what I used when I was studying chemistry. http://www.chemteam.info/Kinetics/WS-Kinetics-first-order-chemical-reactions.html

Answer 2

q.1 why liquid br2 reacts slowly as compared to vapours of bromine?

Think about collision theory. Gas molecules possess more kinetic energy than molecules as a liquid. Gases thus have a larger frequency of collisions and, additionally, are more likely to possess sufficient energy to overcome repulsive forces, (\(i.e. E_a\)). These factors contribute to a greater likelyhood of a successful collision that results in chemical reaction.