# Rates–Practice Questions

Rates of Reactions
Try this 4 question quiz

Which step represents the rate determining step in the following suggested mechanism, in the shown graph?

If the unit of the rate constant ‘k’ for a chemical reaction is Mol L-1 Sec-1. Then the order of the reaction is

When the concentration of a reactant is doubled, the rate of the reaction increases 8 fold, what is the order of this reaction?

The following graph represents the mechanism involved in a chemical reaction. How many elementary steps does the mechanism involve?

Question 1 of 4

1. Define rate
2. Define order of a reaction
3. The rate law for a reaction is as given

Rate = k [A]2[B]

What is the order with respect to A, What is the order with respect to B, What is the overall order?

1. For a multi step reaction how will you determine the order of a reaction?
2. Define half-life of a reaction.
3. If the value of rate constant in a rate law is found to be 2.0 x 10-3 molL-1sec-1 what is the order of the reaction.
4. If the order of the reactant X is ½ and the order of the reactant Y is 3/2 what is the overall order? Write a rate law expression for the reaction.
5. Write the differential rate expression for the reaction
1. A + B $\rightarrow$ C
2. 2A + 3B $\rightarrow$ 2C
6. For the reaction A2 + 3B2 $\rightarrow$ 2AB3 the rate of reaction measured as was found to be 2.4 x 10-4 mol L-1 sec-1 . Calculate the rate of reaction expressed in terms of A2 and B2 (Ans. 1.2 10-4 mol L-1 sec-1 , 3.610-4 mol L-1 sec-1)
7. Ammonia and oxygen reacts at high temperatures as
1. 4NH3 + 5O2 $\rightarrow$ 4NO + 6H2O
2. From the above reaction the following observations were made the concentration of NO increases by 1.08 x 10-2 molL-1 in 3 seconds. Calculate the

i. rate of reaction [3.6 x 10-3 molL-1 sec-1]

ii. rate of disappearance of ammonia [3.6 x 10-3 molL-1sec-1]

iii. the rate of formation of water [5.4 10-3 molL-1 sec-1]

1. If the concentration of a reactant is doubled the rate of the reaction increases 9 by times what is the order of the reaction?
1. A first order reaction is found to have a rate constant k = 7.39 x 10-5 sec-1. Find the half-life of this reaction. [Ans: 9.38x 103 ]
2. For a first order reaction it takes 5 minutes for the initial concentration of 0.6molL-1 to become 0.4molL-1. How long will it take for the initial concentration to become 0.3 mol L [Ans 8.55min]

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