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Aldehydes, Ketones, and Carboxylic Acids — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryAldehydes, Ketones, and Carboxylic Acids4 Marks
Question
Read the passage given below and answer the following questions :
When an aldehyde with no a-hydrogen reacts with concentrated aqueous 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:
  1. A mixture of benzaldehyde and formaldehyde on heating with aqueous NaOH solution gives:
  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. CH3CHO
  2. CH3COCH3
  3. C6H5CHO
  4. C6H5CH2CHO
  1. Trichloroacetaldehyde is subjected to Cannizzaro's reaction by using 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. 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
✓

Answer

  1. (a) Benzyl alcohol and sodium formate.

Explanation:

It is an example of cross Cannizzaro reaction where aromatic aldehyde gets reduced to alcohol and aliphatic aldehyde gets oxidised to its sodium salt (both aldehydes must not contain any αα-hydrogen).

CBSE 12th Chemistry Aldehydes , Ketones and Carboxylic Acids Case Study Questions With Solution 2021

  1. (c) C6H5CHO
  1. (a) 2, 2, 2-trichloroethanol

Explanation:

The Cannizzaro product of given reaction yields 2, 2, 2-trichloroethanol.

CBSE 12th Chemistry Aldehydes , Ketones and Carboxylic Acids Case Study Questions With Solution 2021

  1. (a) Cannizzaro reaction

Explanation:

C - C bond is not formed in Cannizzaro reaction while other reactions result in the formation of C - C bond.

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Read the passage given below and answer the following questions:
The properties of the solutions which depend only on the number of solute particles but not on the nature of the solute are called colligative properties. Relative lowering in vapour pressure is also an example of colligative properties. For an experiment, sugar solution is prepared, for which lowering in vapour pressure was found to be 0.061 mm of Hg. (Vapour pressure of water at 20° C is 17.5 mm of Hg)
The following questions are multiple choice questions. Choose the most appropriate answer:
  1. Relative lowering of vapour pressure for the given solution is.
  1. 0.00348
  2. 0.061
  3. 0.122
  4. 1.75
  1. The vapour pressure (mm of Hg) of solution will be.
  1. 17.5
  2. 0.61
  3. 17.439
  4. 0.00348
  1. Mole fraction of sugar in the solution is.
  1. 0.00348
  2. 0.9965
  3. 0.061
  4. 1.75
  1. If weight of sugar taken is 5g in 108g of water, then molar mass of sugar will be.
  1. 358
  2. 120
  3. 240
  4. 400
  1. The vapour pressure (mm of Hg) of water at 293K when 25g of glucose is dissolved in 450g of water is.
  1. 17.2
  2. 17.4
  3. 17.120
  4. 17.02
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Read the passage given below and answer the following questions:

Arrangement of ligands in order of their ability to cause splitting $(\Delta)$ is called spectrochemical series. Ligands which cause large splitting (large $\Delta$) are called strong field ligands while those which cause small splitting (small $\Delta$) are called weak field ligands. When strong field ligands approach metal atom/ ion, the value of $\Delta_0$ is large, so that electrons are forced to get paired up in lower energy t2g orbitals. Hence, a low-spin complex is resulted from strong field ligand. When weak field ligands approach metal atom/ ion, the value of $\Delta_0$ is small, so that electrons enter high energy eg orbitals rather than pairing in low energy t2g orbitals. Hence, a high-spin complex is resulted from weak field ligands. Strong field ligands have tendency to form inner orbital complexes by forcing the electrons to pair up. Whereas weak field ligands have tendency to form outer orbital complex because inner electrons generally do not pair up.

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.
The following questions are multiple choice questions. Choose the most appropriate answer:

  1. Assertion: In tetrahedral coordination entity formation, the d orbital splitting is inverted and is smaller as compared to the octahedral field splitting.

Reason: Spectrochemical series is based on the absorption of light by complexes with different ligands.

  1. Assertion: In high spin situation, configuration of d5 ions will be $\text{t}^3_{2\text{g}}\text{e}^2_\text{g}.$

Reason: In high spin situation, pairing energy is less than crystal field energy.

  1. Assertion: F- ion is a weak field ligand and fonns outer orbital complex.

Reason: F- ion cannot force the electrons of dz2 and dx2-y2 orbitals of the inner shell to occupy dxy, dyz and dzx orbitals of the same shell.

  1. Assertion: The crystal field model is successful in explaining the formation, structures, colour and magnetic properties of coordination compounds.

Reason: In spectrochemical series, ligands are arranged in a series of increasing field strength.

  1. Assertion: NF3 is a weaker ligand than N(CH3)3.

Reason: NF3 ionizes to give F- ions in aqueous solution.

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Read the passage given below and answer the following questions:
Metal carbonyl is an example of coordination compounds in which carbon monoxide (CO) acts as ligand. These are also called homoleptic carbonyls. These compounds contain both $\sigma$ and $\pi$ character. Some carbonyls have metal-metal bonds. The reactivity of metal carbonyls is due to (i) the metal centre and (ii) the CO ligands. CO is capable of accepting an appreciable amount of electron density from the metal atom into their empty $\pi$ or $\pi-\text{orbital}.$ These types of ligands are called $\pi-\text{accepter}$ or $\pi-\text{acid}$ ligands. These interactions increases the $\Delta_0$ value.
The following questions are multiple choice questions. Choose the most appropriate answer:
  1. What is the oxidation state of metal in [Mn2(CO)10]?
  1. +1
  2. -1
  3. +2
  4. 0
  1. Among the following metal carbonyls, the C-O bond order is lowest in:
  1. [Mn(CO)6]+
  2. [Fe(CO)5]
  3. [Cr(CO)6]
  4. [V(CO)6]-
  1. Which of the following can be reduced easily?
  1. V(CO)6
  2. Mo(CO)6
  3. [Co(CO)4]-
  4. Fe(CO)5
  1. The oxidation state of cobalt in K[Co(CO)4] is:
  1. +1
  2. +3
  3. -1
  4. 0
  1. Structure of decacarbonyl manganese is:
  1. Trigonal bipyramidial
  2. Octahedral
  3. Tetrahedral
  4. Square pyramidal
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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 H2 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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Read the passage given below and answer the following questions:

The phenomenon of the flow of solvent through a semipermeable membrane from pure solvent to the solution is called osmosis.

Sometimes a pressure is applied to stop the process of osmosis, this is known as osmotic pressure. It is denoted by $\pi.$ Osmotic pressure is expressed as : $\pi=\text{CRT}$

Since, osmotic pressure depends upon the molar concentration of solution, therefore it is a colligative property.

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: If red blood cells were removed from the body and placed in pure water, pressure inside the cells increases.

Reason: The concentration of salt content in the cells increases.

  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.

Reason: The total osmotic pressure will be equal to the sum of partial osmotic pressures.

  1. Assertion: When a solution is separated from the pure solvent by a semipermeable membrane, the solvent molecules pass through it from pure solvent side to the solution side.

Reason: Diffusion of solvent occurs from a region of high concentration to a region of low concentration solution.

  1. Assertion: Two solutions having same osmotic pressure at a given temperature are called isotonic solutions.

Reason: Osmotic pressure is not a colligative property.

  1. Assertion: The preservation of meat by salting and fruits by adding sugar protects against bacterial action.

Reason: A bacterium on salted meat or candid fruit loses water due to osmosis shrivels and ultimately dies.

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Give the structures of A and B in the following reactions
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Read the passage given below and answer the following questions:

Williamson's synthesis is used for the preparation of symmetrical as well as unsymmerical ether. It is SN2 reaction mechanism. In Williamson's synthesis, 1º alkyl halide are used for preparation of ethers because 2º and 3º alkyl halide give alkene. Ethers are cleaved by hydrogen halides to alcohol and alkyl halide where alkyl halide is corresponding to that alkyl which has less number of carbon atom (it is because of less steric hindrance). In polar media unsymmetrical ether like tertiary butyl ethyl ether gives ethyl alcohol and tertiary butyl halide as reaction proceeds via carbocation.

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: Rate of reaction of alkyl halide in Williamson's synthesis reaction is 1ºRX > 2ºRX > 3ºRX.

Reason: It is a type of bimolecular substitution reaction (SN2).

  1. Assertion: T-Butyl methyl ether is not prepared by the reaction of t-butyl bromide with sodium methoxide.

Reason: Sodium methoxide is a weak nucleophile.

  1. Assertion: Williamson's synthesis method cannot be used for preparing diphenyl ether.

Reason: Aryl halides do not undergo nucleophilic substitution easily.

  1. Assertion: When isopropyl bromide is treated with sodium isopropoxide, di-isopropyl ether is obtained as a major product.

Reason: With secondary alkyl halides, both substitution and elimination occur.

  1. Assertion: Both symmetrical and unsymmetrical ethers can be prepared by Williamson's synthesis.

Reason: Williamson's synthesis is an example of nucleophilic substitution reaction.

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Read the passage given below and answer the following questions:
Nucleophilic substitution reactions are of two types; substitution nucleophilic bimolecular (SN2) and substitution nucleophilic unimolecular (SN1) depending on molecules taking part in determining the rate of reaction. Reactivity of alkyl halide towards SN1 and SN2 reactions depends on various factors such as steric hindrance, stability of intermediate or transition state, and polarity of solvent. SN2 reaction mechanism is favoured mostly by primary alkyl halide then secondary and then tertiary. This order is reversed in case of SN1 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. C6H5Cl
  2. CH2 = CHCl
  3. ClCH2CH = CH2
  4. CH3CH = CHCl
  1. Isopropyl chloride undergoes hydrolysis by:
  1. SN1 mechanism.
  2. SN2 mechanism.
  3. SN1 and SN2 mechanism.
  4. Neither SN1 nor SN2 mechanism.
  1. The most reactive nucleophile among the following is:
  1. CH3O-
  2. C6H5O-
  3. (CH3)2CHO-
  4. (CH3)3CO-
  1. Tertiary alkyl halides are practically inert to substitution by SN2 mechanism because of:
  1. Insolubility.
  2. Instability.
  3. Inductive effect.
  4. Stearic hindrance.
  1. Which of the following is the correct order of decreasing SN2 reactivity?
  1. RCH2X > R2CHX > R3CX
  2. R3CX > R2CHX > RCH2X
  3. R2CHX > R3CX > RCH2X
  4. RCH2X > R3CX > R2CHX
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Read the passage given below and answer the following questions:
Iron forms many complexes in its +2 and +3 oxidation states such as [Fe(H2O)6]2+ (A); [Fe(CN)6]4- (B); [Fe(H2O)6]3+ (C); [Fe(CN)6]3- (D), etc., They exhibit, different magnetic properties and undergo different hybridisation of iron.
The following questions are multiple choice questions. Choose the most appropriate answer:
  1. Which of the following statements is correct?
  1. (B) is paramagnetic while (C) is diamagnetic.
  2. Both (B) and (D) are outer orbital complexe.
  3. Both (A) and (C) are paramagnetic.
  4. (A) is outer orbital complex and (C) is inner orbital complex.
  1. The complex having maximum magnetic moment is:
  1. (A)
  2. (B)
  3. (C)
  4. (D)
  1. Which of the following does not represent correct configuration of the d-orbitals in the given complexes?
  1. $\text{(A)}:\text{t}^4_{2\text{g}}\text{e}^2_\text{g}$
  2. $\text{(B)}:\text{t}^6_{2\text{g}}\text{e}^0_\text{g}$
  3. $\text{(C)}:\text{t}^4_{2\text{g}}\text{e}^1_\text{g}$
  4. $\text{(D)}:\text{t}^5_{2\text{g}}\text{e}^0_\text{g}$
  1. The spin only magnetic moment of complexes (A), (B), (C) and (D) are respectively (in BM).
  1. $2\sqrt{6},0,\sqrt{35},\sqrt{3}$
  2. $0,2\sqrt{6},\sqrt{35},\sqrt{3}$
  3. $\sqrt{15,}2\sqrt{6},\sqrt{3},0$
  4. $\sqrt{3},\sqrt{8},0,\sqrt{15}$
  1. Which of the given complexes are outer orbital complexes?
  1. (A) and (B) only
  2. (B) and (C) only
  3. (A) and (C) only
  4. (B) and (D) only
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Read the passage given below and answer the following questions:

Carbohydrates can exist in either of two conformations, as determined by the orientation of the hydroxyl group about the asymmetric carbon farthest from the carbonyl.

By convention, a monosaccharide is said to have D-configuration if the hydroxyl group attached to the asymmetric carbon atom adjacent to the -CH2OH group is on the right hand side irrespective of the positions of the other hydroxyl groups. On the other hand, the molecule is assigned L-configuration if the -OH group attached to the carbon adjacent to the - CH2OH group is on the left hand side.

The following questions are multiple choice questions. Choose the most appropriate answer:

  1. D-Glyceraldehyde and L-Glyceraldehyde are:
  1. Epimers.
  2. Enantiomers.
  3. Anomers.
  4. Conformational diasteriomers.
  1. Which of the following monosaccharides, is the majority found in the human body?
  1. D-type.
  2. L-type.
  3. Both of these.
  4. None of these.
  1. The two functional groups present in a typical carbohydrate are:
  1. -OH and -COOH
  2. -CHO and -COOH
  3. >C= O and -OH
  4. -OH and -CHO
  1. Monosaccharides contain:
  1. Always six carbon atoms.
  2. Always five carbon atoms.
  3. Always four carbon atoms.
  4. May contain 3 to 7 carbon atoms.
  1. The correct corresponding order of names of four aldoses with configuration given below respectively, is:

  1. L-erythrose, L-threose, L-erythrose, D-threose.
  2. D-threose, D-erythrose, L-threose, L-erythrose.
  3. L-erythrose, L-threose, D-erythrose, D-threose.
  4. D-erythrose, D-threose, L-erythrose, L-threose.
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