Question

The second order reaction 2A₂B_{3 ----->} A₄B₆ has a rate constant, k, of 7.35 x 10^-3M^-1S-¹ at a certain temperature. If [A₂B₃]₀ = 1.32M, how much time (s) does it take to reduce the concentration to 27% of the original? (please explain)

The decomposition of hydrogen peroxide H₂O₂(l) ---> H₂(g) + O₂(g) has a rate constant of 1.06 x 10-3min^-1. how long (min) will it take for the concentration of H2O2 to decompose by 60%? (please explain)

the decomposition of M3X2(aq) <--> 3M(s) + X2(g) has an activation energy of 15- kJ/mol and (delta)H_rxn = -72kJ/mol, under specified conditions. what is the activation energy (kJ/mol) for the reverse reaction?

the equilibriium constant, Kp has a value of 6.5x10^-4 at 308 K for the reaction of nitrogen monoxide with chlorine.     2NO(g)+Cl₂(g) <---> 2NOCl(g)... at 308K what is the value of Kc? (please explain)

Answer 1

1) The second order reaction 2A₂B_{3 ----->} A₄B₆ has a rate constant, k, of 7.35 x 10^-3M^-1S-¹ at a certain temperature. If [A₂B₃]₀ = 1.32M, how much time (s) does it take to reduce the concentration to 27% of the original? (please explain)

Solution :-

Formula of the second order kinetics is as follows

1/[A]t = K*t + 1/[A]o

Concentration reduced to 27% of the original therefore if we assume 100 % at initial then final is 100 -27 = 73 %

1.32 M * 0.73 = 0.9636 M

Now lets put the values in the formula

1/[A]t = K*t + 1/[A]o

1/[0.9636] = 7.35*10^-3 M-1 s-1 * t + 1/[1.32]

1.04 = 7.35*10^-3 M-1 s-1 * t + 0.7575

1.04-0.7575 = 7.35*10^-3 M-1 s-1 * t

0.2802 /7.35*10^-3 M-1 s-1 = t

38.1 sec =t

Time needed = 38.1 s

2) The decomposition of hydrogen peroxide H₂O₂(l) ---> H₂(g) + O₂(g) has a rate constant of 1.06 x 10-3min^-1. how long (min) will it take for the concentration of H2O2 to decompose by 60%? (please explain)

Solution :- Reaction is first order

Using the first order rate equation we can calculate the time

ln([A]t/[A]o) = - k*t

concentration decreasing by the 60 % means remaining is 100 – 60 = 40 %

so lets put the values in the formula

ln[40/100]= - 1.06*10^3 min-1 * t

-0.9163 = -1.06*10^-3 min-1 * t

-0.9163 / -1.06*10^-3 min-1 = t

864.4 min = t

Therefore time needed is 864.4 min

3) the decomposition of M3X2(aq) <--> 3M(s) + X2(g) has an activation energy of 15- kJ/mol and (delta)H_rxn = -72kJ/mol, under specified conditions. what is the activation energy (kJ/mol) for the reverse reaction?

Solution :- When the reaction is reversed reaction is as follows

Ea reversed rrxn = 15 kJ + 72 kJ = 87 kJ per mol

4) the equilibriium constant, Kp has a value of 6.5x10^-4 at 308 K for the reaction of nitrogen monoxide with chlorine.     2NO(g)+Cl₂(g) <---> 2NOCl(g)... at 308K what is the value of Kc?

   Solution :-

Formula to calculate the Kc from the kp is as follows

Kp = Kc*(RT)^delta n

Delta n = 2- (2+1) =-1

Kc = Kp/RT^delta n

Kc = 6.5*10^-4 / (0.08206 L atm per mol K * 308 K)^-1

Kc= 1.64*10^-2

Therefore the KCc of reaction = 1.64*10^-2