Question
Decrease in concentration of reactant or increase in concentration of product per unit time is called rate of reaction. lt is of two types :
  1. Instantaneous rate of reaction : Rate of change of concentration of reactant or product at a particular time is called instantaneous rate of reaction.
$\text{r}_\text{inst.}=\frac{\text{dC}}{\text{dt}}$
where$, dC =$ infinitely small change in concentration
$dt =$ infinitely small change in time.
  1. Average rate of reaction : Ratio of change in concentration and time required for the change is average rate of reaction.
$\text{r}_\text{av}=\frac{\triangle\text{x}}{\triangle\text{t}}=\frac{\text{Change in concentration}}{\text{Time required for the change}}$
For a reaction of the type$, m_1A + m_2B \rightarrow n_1C + n_2D$
Rate of reaction is given as
$\frac{1}{\text{m}_1}\frac{\text{d[A]}}{\text{dt}}=-\frac{1}{\text{m}_2}\frac{\text{d[B]}}{\text{dt}}=+\frac{1}{\text{n}_1}\frac{\text{d[C]}}{\text{dt}}=+\frac{1}{\text{n}_2}\frac{\text{d[D]}}{\text{dt}}$
In these questions $(Q.$ No. $i-iv),$ a statement of assertion followed by a statement ofreason is given. Choose the correct answer out of the following choices.
  1. Assertion and reason both are correct statements and reason is correct explanation for assertion.
  2. Assertion and reason both are correct statements but reason is not correct explanation for assertion.
  3. Assertion is correct statement but reason is wrong statement.
  4. Assertion is wrong statement but reason is correct statement.
  1. Assertion: The kinetics of the reaction, $\text{mA}+\text{nB}+\text{pC}\rightarrow\text{m}'\text{ X}+\text{n}'\text{ Y}+\text{p}'\text{ Z}$ obey the rate expression as $\frac{\text{dx}}{\text{dt}}=\text{k}[\text{A}]^\text{m}[\text{B}]^\text{n}.$
Reason: The rate of the reaction does not depend upon the concentration of $C$.
  1. Assertion : Instantaneous rate of reaction is equal to $\frac{\text{dx}}{\text{dt}}.$
Reason : lt is the rate of reaction at any particular instant of time.
  1. Assertion : For the reaction, $\text{RCl}+\text{NaOH}\rightarrow\text{ROH}+\text{NaCl},$ the rate of reaction is reduced to half on reducing the concentration of $\ce{RCl}$ to half.
Reason : The rate of reaction is represented by $\ce{k[RCl}].$
  1. Assertion : ln rate law, unlike in the expression for equilibrium constants, the exponents for concentrations do not necessarily match the stoichiometric coefficients.
Reason: It is the mechanism and not the balanced chemical equation for the overall change that governs the reaction rate.
  1. Assertion : ln a reaction$, 2A + B \rightarrow A_2B,$ the reactant $B$ will disappear at twice the rate as $A$ will decrease.
Reason: The rate of disappearance of reactant will be $-\frac{1}{2}\frac{\text{d[A]}}{\text{dt}}=-\frac{\text{d[B]}}{\text{dt}}$

Answer

  1. $(a)$ Assertion and reason both are correct statements and reason is correct explanation for assertion.
Rate expression $\frac{\text{dx}}{\text{dt}}=\text{k}[\text{A}]^\text{m}[\text{B}]^\text{n}$
shows that the total order of reactions is $m + n + 0 = m + n,$ as the rate of reaction is independent of concentration of $C,$ i.e., the order with respect to $C$ is zero. This is the reason that $C$ does not figure in the rate expression.
  1. $(b)$ Assertion and reason both are correct statements but reason is not correct explanation for assertion.
Instantaneous rate of a reaction is equal to small change in concentration $(dx)$ during a small interval of time $(dt)$ at that particular instant of time divided by the time interval.
  1. $(a)$ Assertion and reason both are correct statements and reason is correct explanation for assertion.
For the given reaction, rate of reaction $(r) = \ce{k[RCl}]\ ($where $k$ is rate constant$)$.
Therefore if the concentration of $[\ce{RCl}]$ is reduced to half, then new rate $(\text{r}')=\frac{\text{k}}{2}[\text{RCl}].$
  1. $(a)$ Assertion and reason both are correct statements and reason is correct explanation for assertion.
  1. $(d)$ Assertion is wrong statement but reason is correct statement.
$2A + B \rightarrow A_2B$
The rate of disappearance of reactant will be
$-\frac{1}{2}\frac{\text{d[A]}}{\text{dt}}=\frac{\text{d[B]}}{\text{dt}}=\frac{\text{d}[\text{A}_2\text{B}]}{\text{dt}}$
Therefore, the reactant $B$ will disappear at half the rate as $A$ will decrease.

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  4. None of these.
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  2. $2-$ Butanol
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Read the passage given below and answer the following questions:
Consider the given sequence of reactions:

The following questions are multiple choice questions. Choose the most appropriate answer:
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  6. Fittig reaction.
  7. Ullmann reaction.
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  9. Friedel$-$Crafts acylation reaction.
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  2. Loss of active species on collision.
  3. Low probability of simultaneous collision of all the reacting species.
  4. Increase in entropy and activation energy as more molecules are involved.
  1. The molecularity of the reaction:
$6\text{FeSO}_4+3\text{H}_2\text{SO}_4+\text{KClO}_3\rightarrow\text{KCl}+3\text{Fe}_2(\text{SO}_4)_3+3\text{H}_2\text{O}$ is:
  1. $6$
  2. $10$
  3. $3$
  4. $7$
  1. Which of the following statements is false in the following?
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  3. Molecularity and order always have same values for a reaction.
  4. Order of a reaction depends upon the mechanism of the reaction.
  1. The rate of reaction, $A + 2B \rightarrow$ products, is given by the following equation:
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  1. Assertion: If red blood cells were removed from the body and placed in pure water, pressure inside the cells increases.
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  1. Assertion: The osmotic pressure of a solution obtained by mixing 100mL of 3.4% solution of urea and 100mL of 1.6% solution of cane sugar at 293K is 7.46 bar.
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  1. Assertion: Two solutions having same osmotic pressure at a given temperature are called isotonic solutions.
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  1. Assertion: The preservation of meat by salting and fruits by adding sugar protects against bacterial action.
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  1. Assertion: Tungsten has very high melting point.
Reason: Tungsten is a covalent compound.
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  1. Assertion: Copper metal gets readily corroded in acidic aqueous solution such as $\ce{HCl}$ and dil. $\ce{H_2SO_4}.$
Reason: Free energy change for this process is positive.
  1. Assertion: Tailing of mercury occurs on passing ozone through it.
Reason: Due to oxidation of mercury.
  1. Assertion: Transition metals are poor reducing agents.
Reason: Transition metals fonn numerous alloys with other metals.
Read the passage given below and answer the following questions:
Haloarenes are less reactive than haloalkanes. The low reactivity of haloarenes can be attributed to:
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  • $sp^2$ hybridisation of $C - X$ bond.
  • Polarity of $C - X$ bond
  • Instability of phenyl cation $($formed by self$-$ionisation of haloarene$).$
  • Repulsion between the electron rich attacking nucleophiles and electron rich arenes.
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The following questions are multiple choice questions Choose the most appropriate answer:
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  1. The formation of less stable carbonium ion.
  2. Resonance stabilisation.
  3. Larger carbon$-$halogen bond.
  4. Inductive effect.
  1. Which of the following aryl halides is the most reactive towards nucleophilic substitution?
  1. Which one of the following will react fastest with aqueous $\text{NaOH}$?
  1. Which chloro derivative of benzene among the followings would undergo hydrolysis most readily with aqueous sodium hydroxide to furnish the corresponding hydroxy derivative?
  1. $\ce{C_6H_5Cl}$
  1. The reactivity of the compounds $\ce{(i)\ MeBr, (ii)\ PhCH_2Br, (iii)\ MeCI, (iv)\ p-MeOC_6H_4Br}$ decreases as:
  1. $\ce{(i) > (ii) > (iii) > (iv)}$
  2. $\ce{(iv) > (ii) > (i) > (iii)}$
  3. $\ce{(iv) > (iii) > (i) > (ii)}$
  4. $\ce{(ii) > (i) > (iii) > (iv)}$
The progress of the reaction$, \text{A}\rightleftharpoons\text{nB}$ with time is represented in the following figure :

The following questions are multiple choice questions. Choose the most appropriate answer :
  1. What is the value of $n$?
  1. $1$
  2. $2$
  3. $3$
  4. $4$
  1. Find the value of the equilibrium constant.
  1. $0.6M$
  2. $1.2M$
  3. $0.3M$
  4. $2.4M$
  1. The initial rate of conversion of $A$ will be:
  1. $0.1 mol L^{-1}hr^{-1}$
  2. $0.2 mol L^{-1}hr^{-1}$
  3. $0.4 mol L^{-1}hr^{-1}$
  4. $0.8 mol L^{-1}hr^{-1}$
  1. For the reaction, if $\frac{\text{d}[\text{B}]}{\text{dt}}=2\times10^{-4},$ value of $-\frac{\text{d}[\text{A}]}{\text{dt}}$ will be:
  1. $2 \times 10^{-4}$
  2. $10^{-4}$
  3. $4 \times 10^{-4}$
  4. $0.5 \times 10^{-4}$
  1. Which factor has no effect on rate of reaction?
  1. Temperature.
  2. Nature of reactant.
  3. Concentration of reactant.
  4. Molecularity.
For a first order reaction$, A \rightarrow$ Products$, \text{k}=\frac{2.303}{\text{t}}\log\frac{\text{a}}{\text{a}-\text{x}},$ where a is the initial concentration of $A$ and $(a - x)$ is the concentration of $A$ after time $t. k$ is rate constant. Its value is constant at constant temperature for a reaction. The time in which half of the reactant is consumed is called half$-$life period. Half$-$life period of a first order reaction is constant. Its value is independent of initial concentration or any other external conditions.In these questions $(Q.$ No. $i-iv),$ a statement of assertion followed by a statement ofreason is given. Choose the correct answer out of the following choices.
  1. Assertion and reason both are correct statements and reason is correct explanation for assertion.
  2. Assertion and reason both are correct statements but reason is not correct explanation for assertion.
  3. Assertion is correct statement but reason is wrong statement.
  4. Assertion is wrong statement but reason is correct statement.
  1. Assertion : Rate of reaction doubles when concentration of reactant is doubled if it is a first order reaction.
Reason : Rate constant also doubles.
  1. Assertion : For the first order reaction, half$-$life period is expressed as $\text{t}_\frac{1}{2}=\frac{2.303}{\text{k}}\log2.$
Reason : The half$-$life time of a first order reaction is not always constant and it depends upon the initial concentration of reactants.
  1. Reason : The half$-$life time of a first order reaction is not always constant and it depends upon the initial concentration of reactants.
Reason : Acid only acts as a catalyst whereas alkali acts as one of the reactants.
  1. Assertion : For a first order reaction, the concentration of the reactant decreases exponentially with time.
Reason : Rate of reaction at any time depends upon the concentration of the reactant at that time.
  1. Assertion : Half$-$life period for a first order reaction is independent of initial concentration of the reactant.
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Read the passage given below and answer the following questions:
When an aldehyde with no et $-$ hydrogen reacts with concentrated aqueous $\ce{NaOH},$ half the aldehyde is converted to carboxylic acid salt and other half is converted to an alcohol. In other words, half of the reactant is oxidized and other half is reduced. This reaction is known as Cannizzaro reaction.

The following questions are multiple choice questions. Choose the most appropriate answer:
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  1. Benzyl alcohol and sodium formate.
  2. Sodium benzoate and methyl alcohol.
  3. Sodium benzoate and sodium formate.
  4. Benzyl alcohol and methyl alcohol.
  1. Which of the following compounds will undergo Cannizzaro reaction?
  1. $\ce{CH_3CHO}$
  2. $\ce{CH_3COCH_3}$
  3. $\ce{C_6H_5CHO}$
  4. $\ce{C_6H_5CH_2CHO}$
  1. Trichloroacetaldehyde is subjected to Cannizzaro's reaction by using $\ce{NaOH}$. The mixture of the products contains sodium trichloroacetate ion and another compound. The other compounds is:
  1. $2, 2, 2-$ trichloroethanol.
  2. Trichloromethanol.
  3. $2, 2, 2-$ trichloropropanol.
  4. Chloroform.
  1. In Cannizzaro reaction given below:
$2\text{PhCHO}\xrightarrow{\stackrel{-}{\hbox{ OH}}}\text{PhCH}_2+\text{OH}+\text{PhCO}_2^-$ the slowest step is:
  1. The attack $^-OH$ at the carboxyl group.
  2. The transfer of hydride to the carbonyl group.
  3. The abstraction of proton from the carboxylic group.
  4. The deprotonation of $\ce{PhCH_2OH}.$
  1. Which of the following reaction will not result in the formation of carbon $-$ carbon bonds?
  1. Cannizzaro reaction.
  2. Wurtz reaction.
  3. Reimer $-$Tiemann reaction.
  4. Friedel $-$ Crafts' acylation.