Target: 10 Questions in 10 minutes

An IB Chemistry data booklet is helpful
1. Which of the following can be a unit for the rate constant of a first order reaction?
  • A.   mol dm-3
  • B.   s-1
  • C.   mol dm-3 s-1
  • D.   mol-1 dm3 s-1

2. For the reaction...

2NO(g) + 2H2(g)  → 2N2(g) + 2H2O(g)

..the graph shows how the initial rate of the reaction varies at different concentrations of NO, whilst the concentration of H2 remains constant.

What is the order of the reaction with respect to NO?

Inital rate of NO in reaction
  • A.   0
  • B.   1
  • C.   2
  • D.   3

3. The reaction between sodium thiosulphate and hydrochloric acid is:

Na2S2O3(aq) + 2HCl(aq)  → S(s) + SO2(aq) + 2NaCl(aq) + H2O(l)

Using the following experimental data, what is the rate equation for this reaction?

[Na2S2O3(aq)] / mol dm-3 [HCl(aq)] / mol dm-3 Rate / s-1
0.1 0.1 0.0115
0.1 0.2 0.0117
0.2 0.3 0.0233
  • A.   Rate = k[Na2S2O3(aq)]
  • B.   Rate = k[HCl(aq)]
  • C.   Rate = k[Na2S2O3(aq)][HCl(aq)]
  • D.   Rate = k[Na2S2O3(aq)][HCl(aq)]2

4. Two colourless substances, A and B, react to form a coloured substance C according to the equation 2A + B → C. In a series of experiments with different concentrations of A and B, the initial time to form a small about of C is measured as follows:

[A] / mol dm-3 [B] / mol dm-3 Time / s
0.15 0.2 400
0.3 0.4 100
0.45 0.4 100

What is the rate equation for this reaction?

  • A.   Rate = k[A][B]
  • B.   Rate = k[B]½
  • C.   Rate = k[B]
  • D.   Rate = k[B]2

5. The substitution reaction between 2-bromo-2-methylpropane (CH3)3CBr and sodium hydroxide (NaOH) can be described using the following equation:

(CH3)3CBr + OH-  → (CH3)3COH + Br -

It was found that when the concentration of the halogenoalkane was doubled at constant [OH-], the rate of the reaction doubled. When the concentration of NaOH was tripled as constant [(CH3)3CBr], the rate remained constant.
What is the rate equation for this reaction?

 
  • A.   Rate = k[(CH3)3CBr]
  • B.   Rate = k[(CH3)3CBr][OH-]
  • C.   Rate = k[(CH3)3CBr][Br-]
  • D.   Rate = k[(CH3)3CBr]2
6. The decomposition of N2O to N2 and O2 over platinum catalyst is zero order with respect to N2O. Which of the following graphs represent how the concentration of N2O changes over time in this reaction? 
 
rate of N2O reaction 4 options

7+8: These questions are about the reaction 2NO + O2  → 2NO2 which has the rate equation Rate = k[O2][NO]2.
7. When the concentration of NO is double and the concentration of O2 is halved, how does the rate of the reaction change?
  • A.   It halves.
  • B.   It does not change.
  • C.   It doubles.
  • D.   It quadruples.

8. Which of the following is/are possible mechanisms for this reaction?

I.

NO + NO   right arrow - slow reaction  N2O2

N2O2 + O2   right arrow - fast reaction   2NO2
II.

NO + O2   right arrow - fast reaction   NO3

NO3 + NO   right arrow - slow reaction   2NO2
III.

NO + NO   right arrow - fast reaction   N2O2

N2O2 + O2   right arrow - slow reaction  NO2 + NO + O

NO+ O  right arrow - fast reaction  NO2
  • A.   I only
  • B.   I and II only
  • C.   II and III only
  • D.   I, II and III
9. The decomposition of hydrogen peroxide, H2O2, forms H2O and O2:

2H2O2(aq)  →2H2O(l) + O2(g)

This reaction can be catalysed by potassium iodide, KI, and the rate equation for the catalysed reaction is rate = k[H2O2][I-].

Which of the following statements is correct? 		 
  • A.   The rate of formation of H2O is half that of O2.
  • B.   The reaction is second order with respect to H2O2.
  • C.   The potassium iodide is not involved in the rate determining step of the reaction.
  • D.   The rate constant k is independent of the concentration of H2O2.

10. Propanone (CH3COCH3) reacts with bromine (Br2) in acidic conditions . Below is an accepted mechanism for this reaction:

propanone and bromine reaction diagram

Which of the following statements is/are consistent with this mechanism?

I. The reaction has an overall order of 2
II. The rate determining step is the first step
III. The reaction is zero order with respect to Br2
chemlab
Truman University
  • A.   I only
  • B.   I and II only
  • C.   II and III only
  • D.   I and III only