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92. Ql: 24: Name (CAPS) Q5. Date:- Q1. What is the pll of a 0.29 M solution of m

ID: 1044530 • Letter: 9

Question

92. Ql: 24: Name (CAPS) Q5. Date:- Q1. What is the pll of a 0.29 M solution of maethylamine (CH NHa, 410-) t 25 C Q2. The rate constant for a first-order reaction is 1.8 x 103 s at 692 K and 3.9 X 102 gl at 874 K. What is the activation energy? (R-8314 J/Kmol) Q3. The following reaction is investigated (assume an ideal gas mixture): Initially there are 0.10 mol of NO and 0.25 mol of NJH, in a 10.0-L container. If there are 0.056 mol of N:O at equilibcium, how many moles of Nz are present at equilibrium?

Explanation / Answer

              CH3NH2 + H2O ---------------> CH3NH3^+ (aq) + OH^- (aq)

I              0.29                                       0                       0

C           -x                                             +x                   +x

E          0.29-x                                       +x                   +x

                   Kb     =   [CH3NH3^+][OH^-]/[CH3NH2]

                  4.4*10^-4    = x*x/0.29-x

                 4.4*10^-4 *(0.29-x)   = x^2

                  x   = 0.011

                [OH^-]    = x   = 0.011M

               POH    = -log[OH^-]

                          = -log0.011

                          = 1.9586

                 PH    = 14-POH

                         = 14-1.9586    = 12.0414

2.

K1    = 1.8*10^-2 sec^-1

T1    = 692K

K2   =   3.9*10^-2sec^-1

T2     = 874K

logK2/K1    =   Ea/2.303*R [ 1/T1 -1/T2]

log3.9*10^-2/1.8*10^-2   =   Ea/2.303*8.314 [ 1/692   - 1/874]

0.3357                          = Ea(0.00144-0.00114)/19.147

Ea                                 = 0.3357*19.147/0.0003   = 21426J/mole   = 21.426KJ/mole

3.

                  2N2O    + N2H4 -------------------> 3N2 + 2H2O

        I          0.1       0.25                        0           0

        C       -2*0.022      -0.022                   3*0.022    2*0.022

        E       0.056           0.228                   0.066     0.044

              [N2]   = 0.066mole at equilibrium