Types of Elementary Reactions

Q.

How to balance chemical equations?

Q. For the following reaction $2X+Y\stackrel{k}{\to }P$ the rate of reaction is $\frac{d\left[P\right]}{dt}=k\left[X\right]$. Two moles of $X$ are mixed with one mole of $Y$ to make $1.0L$ of solution. At $50s,0.5\text{mole}$ of $Y$ is left in the reaction mixture. The correct statement(s) about the reaction is(are)
(Use: $ln2=0.693$)

1. The rate constant, $k$, of the reaction is $13.86\times {10}^{-4}{s}^{-1}$
2. Half-life of $X$ is $50s$
3. At $50s$, $-\frac{d\left[X\right]}{dt}=13.86\times {10}^{-4}molL{s}^{-1}$
4. At $100s$, $-\frac{d\left[Y\right]}{dt}=3.46\times {10}^{-3}molL{s}^{-1}$

Q.

In a reaction if the concentration of reactant A is tripled, the rate of reaction becomes twenty seven times. What is the order of the reaction?

Q.

The unit of rate constant of first-order reaction is _________

Q. A second order reaction in which both the reactants have same concentration, is 20% completes in 500 seconds. How much time it will take for 60% completion?

1. 300 seconds
2. 500 seconds
3. 5000 seconds
4. 3000 seconds

Q.

For which of the following order unit of rate of reaction and rate constant are the same?

1. First-order reaction

2. Second-order reaction

3. Third-order recation

4. Zero-order reaction

Q. The reduction of peroxydisulphate ion by $I^{–}$ ion is expressed by $S_2{O}_8^{2-}+3I^{-}\to 2S{O}_4^{2-}+I_3^{-}$
If the rate of disappearance of $I^{–}$ is $9/2\times {10}^{–3}{\text{mol/L}}^{-1}{\text{s}}^{-1}$, what is the rate of formation of $S{O}_4^{2-}$ during the same time?

1. ${10}^{-3}{\text{mol/L}}^{-1}{\text{s}}^{-1}$
2. $2\times {10}^{-3}{\text{mol L}}^{-1}{\text{s}}^{-1}$
3. $3\times {10}^{-3}{\text{mol L}}^{-1}{\text{s}}^{-1}$
4. $4\times {10}^{-3}{\text{mol L}}^{-1}{\text{s}}^{-1}$

Q.

For the elementary reaction M $\to$ N, the rate of disappearance of M increases by a factor of 8 upon doubling the concentration of M. The order of the reaction with respect to M is

1. 4
2. 3
3. 1
4. 2

Q. The half life period for the catalytic decomposition of $A{B}_3$ (g) at 50 mm initial pressure is 4 hrs and at 100 mm initial pressure it is 2 hrs. The order of the reaction is ?

1. 1
2. 0
3. 2
4. 3

Q. (a) What is rate of reaction? Write two factors that affect the rate of reaction.

(b) The rate constant of a first order reaction increases from $4\times {10}^{-2}$ to $8\times {10}^{-2}$ when the temperature changes from ${27}^{\circ }C$ to ${37}^{\circ }C$.
Calculate the energy of activation $\left(E_a\right)$. (log 2 =0.301, log 3 =0.4771, log 4 =0.6021)

Q.

For a reaction $A+B⟶$ Products, the rate law is ---Rate = $k\left[A\right][B{]}^{3/2}$ Can the reaction be an elementary reaction? Explain.

Q.

Which of the following statements are applicable to a balanced chemical equation of an elementary reaction?
(a) Order is same as molecularity
(b) Order is less than the molecularity
(c) order is greater than the molecularity
(d) Molecularity can never be zero

Q.

The rate of first-order reaction is $0.04{\mathrm{mol}}^{-1}{\mathrm{l}}^{-1}{\mathrm{s}}^{-1}$ at $10\mathrm{s}$ and $0.03{\mathrm{mol}}^{-1}{\mathrm{l}}^{-1}{\mathrm{s}}^{-1}$ at $20\mathrm{s}$ after initiation of the reaction. What is the half-life period of the reaction?

Q. Choose the correct option(s) regarding order and molecularity:

1. Molecularity for a particular reaction can be fractional
2. Order for a particular reaction can be fractional
3. Molecularity is defined for elementary reactions only.
4. Order of a reaction is a theoretical value.

Q. The order of reaction $A\to \text{Product}$ can be given by the expression,
[Where r = rate of reaction;
$[A{]}_1=\text{Concentration at time}{t}_1;[A{]}_2=\text{Concentration at time}{t}_2$

1. $\frac{ln{r}_2-ln{r}_1}{ln[A{]}_2-ln[A{]}_1}$
2. $\frac{ln[A_0{]}_2-ln[A_0{]}_1}{ln\left[t_{1/2}\right]-ln[t_{1/2}{]}_1}$
3. $ln\left(\frac{-d\left[A\right]}{k.dt}\right)/ln\left[A\right]$
4. $\frac{ln\left(r/k\right)}{ln\left[A\right]}$

Q. Which of the following statements are true in the case of reversible elementary reactions?

1. Rate of forward reaction is always very large.
2. Rate of backward reaction is very slow in the end.
3. Rate of forward reaction is very large at the beginning.
4. Rate of backward reaction is very slow in the beginning.

Q. $ln$ a first order reaction the concentration of reactant decreases from 800 $mol/d{m}^3$ to 50 $mol/d{m}^3$ is $2\times {10}^4$ sec. The rate constant of reaction in ${\sec }^{-1}$ is:

1. $2\times {10}^4$
2. $3.45\times {10}^{-5}$
3. $1.386\times {10}^{-4}$
4. $2\times {10}^{-4}$

Q. A substance 'A' undergoes decomposition as shown $2A\left(g\right)\to 3B\left(g\right)+C\left(g\right)$. If the rate constant for the decomposition of 'A' is $4\times {10}^{-2}mi{n}^{-1}$ then identify the correct statement(s).

1. The value of $\frac{d\left[C\right]}{dt}=2\times {10}^{-2}\left[A\right]$, where [specie] represents concentration of specie at time t
2. The value of $\frac{d\left[C\right]}{dt}=8\times {10}^{-2}\left[A\right]$, where [specie] represents concentration of specie at time t
3. Rate at which B is being formed is 1.5 times the rate at which A is decomposing
4. Pressure of the gases would never be double of the original in a finite interval of time keeping volume and temperature constant

Q. The decomposition of $N_2{O}_5$ according to the equation $2N_2{O}_5\left(g\right)\to 4N{O}_2\left(g\right)+O_2\left(g\right)$ is a first order reaction. After 30 min, from the start of the decomposition in a closed vessel, the total pressure developed is found to be 284.5 mm Hg. On complete decomposition, the total pressure is 584.5 mm Hg. The rate constant of the reaction is:

1. $5.21\times {10}^{-3}$ min${}^{-1}$
2. $5.12\times {10}^{-3}$ min${}^{-1}$
3. $5.89\times {10}^{-3}$ min${}^{-1}$
4. None of these

Q. $99\%$ at a first-order reaction was completed in $32min.$ when will $99.9\%$ of the reaction complete?

1. $48min$
2. $50min$
3. $46min$
4. $45min$

Q. Rate constant $k=2.303mi{n}^{-1}$ for a particular reaction.The initial concentration of the reaction is $1mol/litre$ then, rate reaction after $1$ minute is:

1. $2.303Mmi{n}^{-1}$
2. $noneofthese$
3. $0.2303Mmi{n}^{-1}$
4. $0.1Mmi{n}^{-1}$

Q. In a reaction, $2A+B\to 3C$, the concentration of $A$ decreases from $0.5mol{L}^{-1}$ to $0.3mol{L}^{-1}$ in $10minutes$. The rate of production of ${}^{\prime }{C}^{\prime }$ during this period is:

1. $0.01mol{L}^{-1}mi{n}^{-1}$
2. $0.04mol{L}^{-1}mi{n}^{-1}$
3. $0.05mol{L}^{-1}mi{n}^{-1}$
4. $0.03mol{L}^{-1}mi{n}^{-1}$
5. $0.02mol{L}^{-1}mi{n}^{-1}$

Q.

Suggest some ways to balance an equation?

Q. Show that time required to complete $99.9\%$ completion of a first order reaction is $1.5$ times to $90\%$ completion.

Q. At ${380}^{\circ }$C, the half-life period for the first-order decomposition of $H_2{O}_2$ is 360 min. The energy of activation of the reaction is 200 kJ mol${}^{-1}$. Calculate the time required for 75% decomposition at ${450}^{\circ }C$?

1. 20.4 minutes
2. 21.6 minutes
3. 30.2 minutes
4. 26.7 minutes

Q. A first order reaction has a rate constant $1.5\times {10}^{-3}se{c}^{-1}$. How long will 5.0 g of this reactant take to reduce to 1.25 g.

1. 924 sec
2. 462 sec
3. 1848 sec
4. none of these

Q. In a catalytic reaction involving the formation of ammonia by Habers process $N_2+3H_2\to 2N{H}_3$, the rate of appearance of $N{H}_3$ was measured as $2.5\times {10}^{-4}mol{L}^{-1}{s}^{-1}$. The rate of disappearance or $H_2$ will be:

1. $2.50\times {10}^{-4}mol{L}^{-1}{s}^{-1}$
2. $1.25\times {10}^{-4}mol{L}^{-1}{s}^{-1}$
3. $3.75\times {10}^{-4}mol{L}^{-1}{s}^{-1}$
4. $5.00\times {10}^{-4}mol{L}^{-1}{s}^{-1}$

Q. Law of Mass action was given by?

1. Avogadro
2. Guldberg-Waage
3. Michelles-Menten
4. None of these

Q. For the first order thermal decomposition reaction, the following data were obtained:
$C_2{H}_{5}C{l}_{\left(g\right)}\stackrel{hv}{\to }{C}_2{H}_{4\left(g\right)}+HC{l}_{\left(g\right)}$
Time (sec) Total pressure (atm)
0 0.30
300 0.50
Calculate the rate constant.(Given: log 2 = 0.301, log3 = 0.4771, log 4 = 0.6021)

Q. From the data given below, determine the rate expression and calculate the rate constant for the reaction. $A\to 2B$

1. Rate = $5.44\times {10}^3{\left[A\right]}^2$
2. Rate = $1.36\times {10}^3{\left[A\right]}^2$
3. Rate = $5.44\times {10}^3\left[A\right]$
4. Rate = $1.36\times {10}^3\left[A\right]$