Chemical Kinetics
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4.12 The decomposition of NH3 on platinum surface is zero order reaction. What are the rates of production of N2 and H2 if k = 2.5 × 10–4 mol–1 L s–1?
4.12 The decomposition of NH3 on platinum surface is zero order reaction. What are the rates of production of N2 and H2 if k = 2.5 × 10–4 mol–1 L s–1?
4.12 2NH3 (g)? N2 (g) + 3H2 (g)
Rate of zero order reaction is equal to rate constant. i.e. Rate = 2.5 * 10-4mol L-1sec-1.
According to rate law,
-d [NH3] / 2dt = d [N2] / dt
2.5 * 10-4mol L-1sec-1 = d [N2] / dt
i.e. the rate of production of N2 is 2.5 * 10-4mol L-1 sec-1.
According to rate law,
-d
Upvote 
4.11 For the reaction 2A + B → A2B the rate = k[A][B]2 with k = 2.0 × 10–6 mol–2 L2 s–1. Calculate the initial rate of the reaction when [A] = 0.1 mol L–1, [B] = 0.2 mol L–1. Calculate the rate of reaction after [A] is reduced to 0.06 mol L–1.
4.11 For the reaction 2A + B → A2B the rate = k[A][B]2 with k = 2.0 × 10–6 mol–2 L2 s–1. Calculate the initial rate of the reaction when [A] = 0.1 mol L–1, [B] = 0.2 mol L–1. Calculate the rate of reaction after [A] is reduced to 0.06 mol L–1.
4.11 (a) Rate = k [A] [B]2, Rate = 0 * 10-6 [0.1] [0.2]2
Rate = 8 * 10-9 mol L-1sec-1
(b) 2A +B = A2B
=0.06+ 0.18 = 0.02
Situation when A remains 0.06 mol L-1
Now, According to rate law, Rate = k [A] [B]2
Rate = 2 * 10-6 [0.06] [0.18]2
i.e. Rate = 3.888 * 10-9 mol L-1sec-1
Initial rate of reaction is 8 * 1
Upvote 4.10 From the rate expression for the following reactions, determine their order of reaction and the dimensions of the rate constants.
(i) 3NO(g) → N2O (g) Rate = k[NO]2
(ii) H2O2 (aq) + 3I– (aq) + 2H+ → 2H2O (l) + 3 I − Rate = k[H2O2 ][I- ]
(iii) CH3CHO (g) → CH4 (g) + CO(g) Rate = k [CH3CHO]3/2
(iv) C2H5Cl (g) → C2H4 (g) + HCl (g) Rate = k [C2H5Cl]
4.10 From the rate expression for the following reactions, determine their order of reaction and the dimensions of the rate constants.
(i) 3NO(g) → N2O (g) Rate = k[NO]2
(ii) H2O2 (aq) + 3I– (aq) + 2H+ → 2H2O (l) + 3 I − Rate = k[H2O2 ][I- ]
(iii) CH3CHO (g) → CH4 (g) + CO(g) Rate = k [CH3CHO]3/2
(iv) C2H5Cl (g) → C2H4 (g) + HCl (g) Rate = k [C2H5Cl]
4.10 (i) 3NO (g)? N2O (g)
Rate = k [NO]2
Here rate law is dependent on concentration of NO only. And power raised to concentration of NO is 2. Hence order of reaction is 2.
To find the dimensions of rate constant (K)- We know the rate of chemical reaction is measured in (concentration / time). So
Upvote 4.9 The activation energy for the reaction 2 HI(g) → H2 + I2 (g) is 209.5 kJ mol–1 at 581K.Calculate the fraction of molecules of reactants having energy equal to or greater than activation energy?
4.9 The activation energy for the reaction 2 HI(g) → H2 + I2 (g) is 209.5 kJ mol–1 at 581K.Calculate the fraction of molecules of reactants having energy equal to or greater than activation energy?
4.9 Given-
Energy of activation, Ea= 209.5 kJ mol–1
Ea in joules = 209.5 × 1000 = 209500 J mol–1
Temperature, T = 581K
Gas constant, R = 8.314 J K-1 mol-1
Using the Arrhenius equation,
k = Ae-Ea/RT
In this equation, the term e-Ea/RT represents the number of molecules which have kinetic energy greater than
Upvote 4.8 The rate of the chemical reaction doubles for an increase of 10K in absolute temperature from 298K. Calculate Ea .
4.8 The rate of the chemical reaction doubles for an increase of 10K in absolute temperature from 298K. Calculate Ea .
4.8 Given-
Initial temperature, T1 = 298 K
Final temperature, T2 = 298 K + 10 K = 308 K
Knowing that the rate constant of a chemical reaction normally increases with increase in temperature, we assume that,
Initial value of rate constant, k1 = k
Final value of rate constant, k2 = 2k
Using Arrhenius
Upvote 4.7 What will be the effect of temperature on rate constant?
4.7 What will be the effect of temperature on rate constant?
4.7 The rate constant of a chemical reaction normally increases with increase in temperature. It is observed that for a chemical reaction with rise in temperature by 10°C, the rate constant is nearly doubled and this temperature dependence of the rate of a chemical reaction can be accurately ex
Upvote 4.6 Time required to decompose SO2Cl2 to half of its initial amount is 60 minutes. If the decomposition is a first order reaction, calculate the rate constant of the reaction.
4.6 Time required to decompose SO2Cl2 to half of its initial amount is 60 minutes. If the decomposition is a first order reaction, calculate the rate constant of the reaction.
4.6 Given-
t1/2 = 60 mins
Using the formula for half life, t1/2 = 0.693/k, we get,
k= 0.693 / t1/2
k= 0.693 / 60
∴k = 1.155 × 10-2 min-1
The rate constant of the reaction, k is 1.155 × 10-2 min-1
Upvote 4.5 A first order reaction has a rate constant 1.15 × 10-3 s-1. How long will 5 g of this reactant take to reduce to 3 g?
4.5 A first order reaction has a rate constant 1.15 × 10-3 s-1. How long will 5 g of this reactant take to reduce to 3 g?
4.5 Given-
Rate constant, k = 1.15 * 10-3 s-1
innitial quantity R0 = 5g
Final quantity, R = 3 g
According to the formula of first order reaction
K = 2.303/ t log R0 / R
1.15 X 10-3 = 2.303 /t log 5/3
t = 2.303 / 1.15 X 10-3 log 5/3
t = 443.8 s
t = 4.438 * 102 s
The time taken for 5g of the reactant
Upvote 4.4 The conversion of molecules X to Y follows second order kinetics. If concentration of X is increased to three times how will it affect the rate of formation of Y?
4.4 The conversion of molecules X to Y follows second order kinetics. If concentration of X is increased to three times how will it affect the rate of formation of Y?
4.4 Let the reaction be X→Y
As this reaction follows second order kinetics, the rate of the reaction will be,
Rate = k (X)2 → Equation 1
Since the concentration of X is increased three times, Equation 1 will become,
Rate = k (3X)2
= k × 9 (X)2
∴ The rate of formation of Y will become 9 times.
Thus, the r
Upvote 4.3 For a reaction, A + B → Product; the rate law is given by, r = k [ A]1/2 [B]2 . What is the order of the reaction?
4.3 For a reaction, A + B → Product; the rate law is given by, r = k [ A]1/2 [B]2 . What is the order of the reaction?
4.3 The order of the reaction is sum of the powers of concentration of reactants in the rate law. According to this,
The order of the reaction = 1/2 + 2
= 2 1/2 or 2.5
The order of the reaction is 2.5
Upvote