Tutorial: Chemical Kinetics

Tutorial: Chemical Kinetics

1.	The reaction of nitric oxide with hydrogen at 1280 °C is 2NO (g)    +    2H2 (g)    ­®    N2 (g)    +    2H2O (g) From the following data collected at this temperature, determine :
	(a)	The rate law
	(b)	The rate constant
	(c)	The rate of the reaction when [NO] = 12.0 x 10-3 M and [H2] = 6.0 x 10-3 M
		Experiment [NO] (M) [H2] (M) Initial rate (M/s) 1 5.0 x 10-3 2.0 x 10-3 1.3 x 10-5 2 10.0 x 10-3 2.0 x 10-3 5.0 x 10-5 3 10.0 x 10-3 4.0 x 10-3 10.0 x 10-5
2.	The rate of the reaction between haemoglobin (Hb) and carbon monoxide (CO) was studied at 20 °C. The following data were collected with all concentration units in mmol/L. (A haemoglobin concentration of 2.21 mmol/L is equal to 2.21x 10-6 mol/L) [Hb]0 (mmol/L) [CO]0 (mmol/L) Initial Rate  (mmol/L.s) 2.21 1.00 0.619 4.42 1.00 1.240 4.42 3.00 3.710
	(a)	Determine the orders of this reaction with respect to Hb and CO.
	(b)	Determine the rate law.
	(c)	Calculate the value of the rate constant.
	(d)	What would be the initial rate for an experiment with [Hb]0 = 3.36 mmol/L and [CO]0 = 2.40 mmol/L?
3.		The graph represents the decomposition of of H2O2 at 45 °C. 2H2O2 (l)    ®    2H2O (l)    +    O2 (g)
	(a)	i.     Express the order of the reaction ii.     Determine the initial concentration of H2O2. iii.     Calculate the concentration of H2O2 after 10 hours.
	(b)	Calculate the initial rate of formation of H2O, given the rate constant is 1.0 x 10-3 min-1
4.		Write the rate expressions for the following reactions in terms of the disappearance of the reactants and the appearance of the products: (i)                 I- (aq)    +    OCl- (aq)    ®    Cl- (aq)    +    OI- (aq) (ii)               4NH3 (g)    +    5O2 (g)    ®    4NO (g)    +    6H2O (g)
5.		Consider the reaction 4NO2 (g)    +    O2 (g)    ®    2N2O5 (g) Suppose that, at particular moment during the reaction, molecular oxygen is reacting at the rate of 0.024 M/s. (i)                 At what rate is N2O5 being formed? (ii)               At what rate is NO2 reacting?
6.		Write a balanced equation for a gas – phase reaction whose rate is given by: Rate =
		CH2
7.		®       CH3 – CH = CH2 CH2   CH2                     Cycloropane                  Propene The conversion of cyclopropane to propene in the gas phase is a first – order reaction with a rate constant of  s-1 at 500 °C. (a)    If the initial concentration of cyclopropane was 0.25 M, what is the concentration after 8.8 min? (b)   How long (in minutes) will it take for the concentration of cyclopropane to decrease from 0.25 M to 0.15 M? (c)    How long (in minutes) will it take to convert 74 percent of the starting material?
8.		The reaction 2A    ®    B is first order in A with a rate constant of s-1 at 80 °C. How long (in seconds) will it take for A to decrease from 0.88 M to 0.14 M?
9.		A certain first – order reaction is 35.5 percent complete in 4.90 min at 25 °C. what is its rate constant?
10.		The decomposition of ethane (C2H6) to methyl radicals is a first – order reaction with a rate constant of at 700 °C: C2H6(g)    ®    2 CH3(g) Calculate the half – life of the reaction in minutes.
11.		Given rate constant of the first – order decomposition of nitrogen pentoxide in carbon tethrachloride (CCl4) solvent at 45 °C is 5.7 x 10-4 s-1 and the reaction:  2 N2O5(CCl4)    ®    4 NO2(g)    +    O2(g) Calculate the half – life of the decomposition of N2O5.
12.		The thermal decomposition of phosphine (PH3) into phosphorus and molecular hydrogen is a first order reaction: 4 PH3 (g)    ®    P4 (g)    +    6 H2(g) The half – life of the reaction is 35.0 s at 680 °C. Calculate: (i)                 The first – order rate constant for the reaction (ii)               The time required for 95 percent of the phosphine to decompose.
13.		Iodine atoms combine to form molecular iodine in the gas phase I(g)    +    I(g)    ®    I2(g) This reaction follows second order kinetics and has the high rate constant 7.0 x 109 /M.s at 23 °C. (i)    If the initial concentration of I was 0.086 M, calculate the concentration after 2.0 min. (ii)  Calculate the half – life of the reaction if the initial concentration of I is 0.60 M and if it is 0.42 M. (iii)
14.		The reaction  2A    ®    B is second order with a rate constant of 51 M-1min-1 at 24 °C. (i)                 Starting with [A]0 = 0.0092 M, how long will it take for [A]t = 3.7 x 10-3 M? (ii)               Calculate the half – life of the reaction.