Elementary and Complex Reactions

Q. If half life of a first order reaction is 10 min then how much time it takes for 87.5% completion of reaction Options: 10 min 20 min Should have chosen 30 min 40 min

Q.

What are some examples of fast chemical reactions?

Q. The decomposition of ozone proceeds as $O_3\iff O_2+O\left(fast\right)O+O_3\to 2O_2\left(slow\right)$
The rate expression should be

1. $r=k[O_3{]}^2$
2. $r=k\left[O_3{]}^2\right[O_2{]}^{-1}$
3. $r=k\left[O_3\right]\left[O_2\right]$
4. $r=k\left[O_3\right][O_2{]}^{-1}$

Q.

Which of the following is multimolecular colloid

A.)lyophilic Sol B.)starch C.) gold Sol. D) soap solution

Q.

If $75\%$ of a first order reaction was completed in $90\mathrm{minutes},60\%$ of the same reaction would be completed in approximately $(\mathrm{in}\mathrm{minutes})$_______. (take:$\log 2=0.30;\log 2.5=0.40)$.

Q. The half life period (${\text{t}}_{1/2}$) of a reaction is halved as the initial concentration of the reactant is doubled. What is the order of the reaction ?

Q. In the reaction, $N{H}_{4}N{O}_2(aq.)\to N_2\left(g\right)+2H_{2}O\left(l\right)$, the volume of $N_2$ after $20\text{min}$ and after a long time is $40\text{mL}$ and $70\text{mL}$ respectively. The value of rate constant is:
(Given: Order of reaction = First order)

1. $\left(\frac{1}{20}\right)\log \left(\frac{7}{4}\right)mi{n}^{-1}$
2. $\left(\frac{2.303}{1200}\right)\log \left(\frac{7}{3}\right){\sec }^{-1}$
3. $\left(\frac{1}{20}\right)\log \left(\frac{7}{3}\right){min}^{-1}$
4. $\left(\frac{2.303}{20}\right)\log \left(\frac{11}{7}\right){min}^{-1}$

Q.

For a complex reaction ......... .

(a) order of overall reaction is same as molecularity of the slowest step
(b) order of overall reaction is less than the molecularity of the slowest step
(c) order of overall reaction is greater than molecularity of the slowest step
(d) molecularity of the slowest step is never zero or non-integer

Q. For the reaction equilibrium
$N_2{O}_4\left(g\right)\rightleftharpoons 2N{O}_2\left(g\right)$ the concentrations of $N_2{O}_4$ and $N{O}_2$ at equilibrium are $4.8\times {10}^{-2}$ and $1.2\times {10}^{-2}mol{L}^{-1}$ respectively. The value of $K_c$ for the reaction is

1. $3\times {10}^{-1}mol{L}^{-1}$
2. $3\times {10}^{-3}mol{L}^{-1}$
3. $3\times {10}^{3}mol{L}^{-1}$
4. $3.3\times {10}^{2}mol{L}^{-1}$

Q.

Is concentration directly proportional to rate of reaction?

Q.

For which type of reactions, order and molecularity have the same value?

Q.

Rate law cannot be determined from balanced chemical equation if.....
(a) reverse reaction is involved
(b) it is an elementary reaction
(c) it is a sequence of elementary reactions
(d) any of the reactants is in excess

Q.

List the various differences between Order and Molecularity of a reaction

Q. Lindemann proposed the following detailed mechanism for gas phase isomerization, the reaction is

In the above scheme, $A^{\ast }$ is a molecule that has enough vibrational energy to decompose or isomerise. The Lindemann mechanism is followed by most of gas phase decomposition or isomerization reaction.
For the overall unimolecular isomerization of cyclopropane to propylene at , the values of versus concentration is as follows.
$\underset{k_{unit}}{\left|M\right|}\underset{\frac{1}{137.5}}{\left|1M\right|}\underset{\frac{1}{131.25}{\text{in s}}^{-1}}{\left|2M\right|}$

As per Lindemann mechanism $k_{unit}$ is

1. $k_{unit}=\frac{k_1{k}_2}{k_{-1}}$
2. $\frac{1}{k_{unit}}=\frac{k_{-1}}{k_1{k}_2}+\frac{k_1}{\left[M\right]}$
3. $\frac{1}{k_{unit}}=\frac{k_{-1}}{k_1{k}_2}+\frac{\left[M\right]}{k_1}$
4. $\frac{1}{k_{unit}}=\frac{k_{-1}}{k_1{k}_2}+\frac{1}{k_1}\times \frac{1}{\left[M\right]}$

Q. 24. Why tyndall effect is more effectively shown by lyophobic colloid?

Q. A reaction ${\text{A}}_2+{\text{B}}_2\to \text{2AB}$ occurs by the following mechanism

${\text{A}}_2\to \text{A +A (slow)}{\text{A + B}}_2\to \text{AB + B (fast)}\text{A+ B}\to \text{AB (fast)}$

The order of reaction would be

1. $\frac{3}{2}$
2. $1$
3. Zero
4. $2$

Q. For a given reaction:
$R\to P$
following graph was obtained between concentration of reactant , $R$ w.r.t time.

The value for average rate $inmol{L}^{-1}{s}^{-1}$ from $t_1=10min$ to $t_2=15min$ is :

Q. 9. 87.5% of a first order reaction is completed in 45 minutes. The time in which 99.9 % of the reaction will be completed is

Q. The chemical reaction, $2O_3\to 3O_2$ proceeds as follows;
$O_3\rightleftharpoons O_2+O$ ....(Fast)
$O+O_3\to 2O_2$ ....(Slow)
The rate law expression should be:

1. $r=K[O_3{]}^2$
2. $r=K\left[O_3{]}^2\right[O_2{]}^{-1}$
3. unpredictable
4. $r=K\left[O_3{]}^{[}{O}_2\right]$

Q.

A large value of equilibrium constant K shows that

1. The reaction has not yet started

2. The reaction has gone to near completion towards left

3. nothing can be said

4. The reaction has gone near to completion towards right

Q.

What causes Brownian motion in colloidal dispersion?

Q. The reaction $A_2+B_2\to 2\mathrm{AB}$, is bound to obey the following mechanism
$A_2\stackrel{k_1}{\underset{k_{-1}}{\rightleftarrows }}A+A\left(\mathrm{fast}\right)$
$A+B_2\stackrel{k_2}{\to }\mathrm{AB}+B\left(\mathrm{slow}\right)$
$A+B\to \mathrm{AB}\left(\mathrm{fast}\right)$
The order of overall reaction is

1. 3
2. 2
3. 2.5
4. 1.5

Q. What is limiting reagent ?

Q. 9. An ester A on hydrolysis produces one acid B and an alcohol C . B can reduce feling solution .C on oxidation produces B .Identify A, B, C.

Q. The decomposition of ozone proceeds as $O_3\iff O_2+O\left(fast\right)O+O_3\to 2O_2\left(slow\right)$
The rate expression should be

1. $r=k\left[O_3\right][O_2{]}^{-1}$
2. $r=k\left[O_3\right]\left[O_2\right]$
3. $r=k\left[O_3{]}^2\right[O_2{]}^{-1}$
4. $r=k[O_3{]}^2$

Q.

Identify the INCORRECT statement.

1. The overall rate of reaction is determined by the rate of the fastest elementary step.

2. The rate constant of a typical reaction doubles with a 10°C rise in temperature.

3. The reaction mechanism is a step-by-step pathway by which reaction occurs

4. The reaction mechanism is typically a series of elementary reaction steps.

Q. What is slow and fast reaction? Give example.

Q. The rate of dissappearance of $S{O}_2$ in the reaction $2S{O}_2+O_2\to 2S{O}_3$ is $1.28\times {10}^{-3}g/sec$. Then the rate of formation of $S{O}_3$ is :

1. $0.64\times {10}^{-3}g/sec$
2. $1.28\times {10}^{-3}g/sec$
3. $0.80\times {10}^{-3}g/sec$
4. $1.60\times {10}^{-3}g/sec$

Q.

Write the chemical formulae and hence balance the following word equation:

Calcium Hydrogen Carbonate $\stackrel{∆}{\to }$ Calcium Carbonate + Water + Carbon dioxide

Q.

The sign used to indicate reversible reaction is.

1. $\to$

2. $\rightleftharpoons$

3. $\leftarrow$

4. $=$