# Rates–Practice Questions

Rates of Reactions
Try this 4 question quiz

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

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

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

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

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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