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Haloalkanes and Haloarenes — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryHaloalkanes and Haloarenes4 Marks
Question
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:
  1. Identify W.
  1. Compound Y is:
  1. When X reacts with $CH_3COCl$ in presence of anhy. $AlCl_3$, the reaction is known as:
  1. Fittig reaction.
  2. Ullmann reaction.
  3. Wurtz-Fittig reaction.
  4. Friedel-Crafts acylation reaction.
  1. When X is treated Ni-Al/ NaOH the product obtained is:
  1. Benzene.
  2. Phenol.
  3. P-chlorophenol.
  4. Triphenyl.
  1. Compound Z is:
  1. Phenol.
  2. P-chlorophenol.
  3. P-nitrophenol.
  4. Nitrobenzene.
✓

Answer

  1. (c)

Explanation:
  1. (c)

​​​​​​​Explanation:
  1. (d) Friedel-Crafts acylation reaction.
  2. (a) Benzene.
​​​​​​​​​​​​​​Explanation:
  1. (c) P-nitrophenol.

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The electrochemical cell shown below is concentration cell.
$M \mid M ^{2+}$ (saturated solution of a sparingly soluble salt, $\left.MX _2\right)\left|\left| M ^{2+}\left(0.001 mol dm ^{-3}\right)\right| M\right.$ The emfof the cell depends on the difference in concentrations of $M ^{2+}$ ions at the two electrodes. The emf of the cell at 298 K is 0.059 V . The following questions are multiple choice questions. Choose the most appropriate answer:
  1. The solubility product ($K_{sp'} mol^3 dm^{-9})$ of $MX_2$ at 298 K based on the information available for the given concentration cell is $(\text{take }2.303 \times \text{R}\times \frac{298}{\text{F}} = 0.059)$
  1. $2 \times 10^{-15}$
  2. $4 \times 10^{-15}​​​​​​​$
  3. $3 \times 10^{-12}​​​​​​​$
  4. $1 \times 10^{-12}​​​​​​​$
  1. The value of $\triangle\text{G}$ (in kJ $mol^{-1}​​​​​​​$) for the given cell is (take $1 F = 96500 C mol^{-1})$
  1. 3.7
  2. -3.7
  3. 10.5
  4. -11.4
  1. The equilibrium constant for the foUowing reaction is:
$\text{Fe}^{2+}+\text{Ce}^{4+}\rightleftharpoons\text{Ce}^{3+}+\text{Fe}^{3+}$

(Given, $\text{E}^\circ_\frac{\text{Ce}^{4+}}{\text{Ce}^{3+}}=1.44\text{V}$ and $\text{E}^\circ_\frac{\text{Fe}^{3+}}{\text{Fe}^{2+}}=0.68\text{V}$)
  1. $7.6 \times 10^{12}$​​​​​​​
  2. $6.5 \times 10^{10}$
  3. $5.2 \times 10^9$
  4. $3.4 \times 10^{12}​​​​​​​$
  1. The solubility product of a saturated solution of $Ag_2CrO_4 $in water at 298 K if the emf of the cell
$Ag|Ag^+ (satd. Ag_2CrO_4 soln) || Ag^+ (0.1 M) | Ag$

is 0.164V at 298 K, is:
  1. $3.359 \times 10^{-12} mol^3 L^{-3}$​​​​​​​
  2. $2.287 \times 10^{-12} mol^3 L^{-3}$
  3. $1.158 \times 10^{-12} mol^3 L^{-3}$
  4. $4.135 \times 10^{-12} mol^3 L^{-3}$
  1. To calculate the emf of the cell, which of the foUowing options is correct?
  1. emf $= E_{cathode}- E_{anode}$​​​​​​​
  2. emf $= E_{anode}- E_{cathode}$
  3. emf $= E_{anode} + E_{cathode}$
  4. None of these.
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Two types of conductors are generally used, metallic and electrolytic. Free electrons are the current carrier in metallic and in electrolytic conductors, free ions. Specific conductance or conductivity of an electrolytic solution is given by
$\text{K}=\text{C}\times\frac{\text{l}}{\text{A}}$
where, $\text{C}\times\frac{1}{\text{R}}$ and $\frac{\text{l}}{\text{A}}=\text{G}^\star$ (cell constant)
Molar conductance $(\wedge_\text{m})$ and equivalent conductance $(\wedge_\text{e})$ of an electrolyte solution are calculated as
$\wedge_\text{m}=\frac{\text{K}\times1000}{\text{M}}$ or $\wedge_\text{e}=\frac{\text{K}\times1000}{\text{N}}$
where, M = molarity of solution and N is normality of solution. Molar conductance of strong electrolyte depends on the concentration.
$\wedge_\text{m}=\wedge^\circ_{\text{m}^-}\text{b}\sqrt{\text{C}}$
$\wedge^\circ_\text{m}=$ molar conductance at infinite dilution, b = constant, C = cone.of solution
In these questions (Q. No. i-iv), a statement of assertion followed by a statement of reason 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 molar conductivity of strong electrolyte decreases with increase in concentration.
Reason: At high concentration, migration ofions is slow.
  1. Assertion: The molar conductance of weak electrolyte at infinite dilution is equal to the sum of molar conductance of cations and anions.
Reason: Kohlrausch's law is applicable for strong electrolytes.
  1. Assertion: Equivalent conductance of all electrolytes increases with increasing concentration.
Reason: More number ofions are available per gram equivalent at higher concentration.
  1. Assertion: Specific conductance decreases with dilution whereas equivalent conductance increases.
Reason: On dilution, number of ions per millilitre decreases but total number ofions increases considerably.
  1. Assertion: The ratio of specific conductivity to the observed conductance does not depend upon the concentration of the solution taken in the conductivity cell.
Reason: Specific conductivity decreases with dilution whereas observed conductance increases with dilution.
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For a first order reaction, A → 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.
Reason: For a first order reaction, $\text{t}_\frac{1}{2}=\frac{0.693}{\text{k}},$ where k is rate constant.
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The potential of each electrode is known as electrode potential. Standard electrode potential is the potential when concentration of each species taking part in electrode reaction is unity and the reaction is taking place at 298K. By convention, the standard electrode potential of hydrogen (SHE) is $0.0V.$ The electrode potential value for each electrode process is a measure of relative tendency of the active species in the process to remain in the oxidised/ reduced form. The negative electrode potential means that the redox couple is stronger reducing agent than $\frac{\text{H}^+}{\text{H}_2}$ couple. A positive electrode potential means that the redox couple is a weaker reducing agent than the $\frac{\text{H}^+}{\text{H}_2}$ couple. Metals which have higher positive value of standard reduction potential form the oxides of greater thermal stability.
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: An electrochemical cell can be set-up only if the redox reaction is spontaneous.
Reason: A reaction is spontaneous if the free energy change is negative.
  1. Assertion: The standard electrode potential of hydrogen is $0.0V.$
Reason: It is by convention.
  1. Assertion: The more negative is the standard reduction potential, greater is its ability to displace $H_2$ from acid.
Reason: Strength of reducing agent increases with the increase in negative value of the standard reduction potential.
  1. Assertion: The negative value of standard reduction potential means that reduction takes place on this electrode with reference to hydrogen electrode.
Reason: The standard electrode potential of a half cell has a fixed value.
  1. Assertion: The absolute value of electrode potential cannot be determined experimentally.
Reason: The electrode potential values are generally determined with respect to SHE.
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Explain the D and L notation method of spatial arrangement with respect to glucose.
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Explain the structure of nucleic acid compounds.
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Read the passage given below and answer the following questions:
Nucleophilic substitution reactions are of two types; substitution nucleophilic bimolecular $(S_N2)$ and substitution nucleophilic unimolecular $(S_N1)$ depending on molecules taking part in determining the rate of reaction. Reactivity of alkyl halide towards $S_N1$ and $S_N2$ reactions depends on various factors such as steric hindrance, stability of intermediate or transition state, and polarity of solvent. $S_N2$ reaction mechanism is favoured mostly by primary alkyl halide then secondary and then tertiary. This order is reversed in case of $S_N1$ reactions.
The following questions are multiple choice questions. Choose the most appropriate answer:
  1. Which of the following is most reactive towards nucleophilic substitution reaction?
  1. $C_6H_5Cl$
  2. $CH_2 = CHCl$
  3. $ClCH_2CH = CH_2$
  4. $CH_3CH = CHCl$
  1. Isopropyl chloride undergoes hydrolysis by:
  1. $S_N1$ mechanism.
  2. $S_N2$ mechanism.
  3. $S_N1$ and $S_N2$ mechanism.
  4. Neither $S_N1$ nor $S_N2$ mechanism.
  1. The most reactive nucleophile among the following is:
  1. $CH_3O^-$
  2. $C_6H_5O^-$
  3. $(CH_3)_2CHO^-$
  4. $(CH_3)_3CO^-$
  1. Tertiary alkyl halides are practically inert to substitution by $S_N2$ mechanism because of:
  1. Insolubility.
  2. Instability.
  3. Inductive effect.
  4. Stearic hindrance.
  1. Which of the following is the correct order of decreasing $S_N2$ reactivity?
  1. $RCH_2X > R_2CHX > R_3CX$
  2. $R_3CX > R_2CHX > RCH_2X$
  3. $R_2CHX > R_3CX > RCH_2X$
  4. $RCH_2X > R_3CX > R_2CHX$
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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:
  • Resonance effect.
  • $sp^2$ 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.
Reactivity of haloarenes can be increased or decreased by the presence of certain groups at certain positions for example, nitro ($-NO_{^2}$) group at o/ p positions increases the reactivity of haloarenes towards nucleophilc substitution reactions.
The following questions are multiple choice questions Choose the most appropriate answer:
  1. Aryl halides are less reactive towards nucleophilic substitution reaction as compared to alkyl halides due to
  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 $NaOH$?
  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. $C_6H_5Cl$
  1. The reactivity of the compounds (i) $MeBr$, (ii) $PhCH_2Br$, (iii) $MeCI$, (iv) $p-MeOC_6H_4Br$ decreases as:
  1. (i) > (ii) > (iii) > (iv)
  2. (iv) > (ii) > (i) > (iii)
  3. (iv) > (iii) > (i) > (ii)
  4. (ii) > (i) > (iii) > (iv)
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Read the passage given below and answer the following questions:
The halogen elements show great resemblances to one another in their chemical behaviour and properties of their compounds with other elements. There is, however, a progressive change in properties from F through $Cl, Br,$ and I to At. F is most reactive among the halogens and in fact, from all other elements and it has certain other properties that set it apart from the other halogens.
In these questions (Q.No. i - iv), a statement of assertion followed by a statement of reason 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: $F_2 $ has high reactivity.
Reason: $F_2$ has low bond dissociation enthalpy.
  1. Assertion: The bond between $F - F$ is weaker than between $Cl - Cl.$
Reason: Atomic size of $F$ is smaller than that of $Cl.$
  1. Assertion: Fluoride does not show oxidation number greater than zero.
Reason: The halogens chlorine, bromine and iodine can show positive oxidation state of $+1, +3$ and $+7.$
  1. Assertion: F atom has less negative electron affinity than Cl atom.
Reason: Additional electrons are repelled more effectively by $3p-$electrons in $Cl$ than by $2p-$electrons in Fatom.
  1. Assertion: Fluorine is strongest oxidising agent in halogens.
Reason: It displaces other halogens from its aqueous solution.
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Read the passage given below and answer the following questions:
Transition elements are elements that have partially filled d-orbitals. The configuration of these elements corresponds to $(n - 1)d^{1-10}ns^{1-2}.$ It is important to note that the elements mercury, cadmium and zinc are not considered transition elements because of their electronic configurations, which corresponds to $(n - 1)d^{10}ns^2.$ Some general properties of transition elements are:
These elements can fonn coloured compounds and ions due to $d-d$ transition;
These elements exhibit many oxidation states;
A large variety of ligands can bind themselves to these elements, due to this, a wide variety of stable complexes formed by these ions. The boiling and melting point of these elements are high. These elements have a large ratio of charge to the radius.
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: Tungsten has very high melting point.
Reason: Tungsten is a covalent compound.
  1. Assertion: $Zn, Cd$ and $Hg$ are normally not considered transition metals.
Reason: d-Orbitals in $Zn, Cd$ and $Hg$ elements are completely filled, hence these metals do not show the general characteristics properties of the transition elements.
  1. Assertion: Copper metal gets readily corroded in acidic aqueous solution such as $HCl$ and dil. $H_2SO_4.$
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.
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