Chemistry

Chemical Compounds and Reactions

505 Questions

Chemical compounds and reactions involve understanding the properties, colors, and formation of various chemical substances. Questions focus on identifying precipitates, observing color changes during reactions, and naming common compounds. This topic is a fundamental part of the chemistry syllabus for competitive exams.

identifying precipitateschemical reaction colorscompound namingcolloidal particle propertiesacid base reactions

Chemical Compounds and Reactions Questions

Multiple choice

Which among the following transition metal ions are colourless?

  1. Sc3+
  2. Mn2+
    3. Hg2+ 4. Fe3+ 5. Cu+

  1. 1, 2 and 3

  2. 1, 3 and 5

  3. 2, 3 and 4

  4. 2, 4 and 5

  5. 3, 4 and 5
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Transition metal ions exhibit colour due to the presence of unpaired electrons in (n−1) d-orbitals which undergo d-d transition. The metal ions not having unpaired electrons (n−1)d0 or having completely filled d orbital (n−1)d10 do not absorb radiations in visible region, since d-d transitions are not possible. Hence, they are colourless ions. Sc3+ (3d0), Cu+ (3d10), and Hg2+ (5d10): All are colourless

Multiple choice

Which of the following produces reddish brown precipitate?

  1. Formic acid and tollen reagent

  2. Formic acid and fehling solution

  3. 2-pentanone is catalysed by I2+NaOH/NaOI

  4. 3-pentanone

  5. Only option (3) and (4)
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This option is correct because formic acid and Fehling solution react to produce cuprous oxide, which gives reddish brown precipitate.

Multiple choice

During the preparation of acetanilide from aniline, a small amount of Zn is added to the reaction mixture because

  1. zinc induces the precipitation

  2. zinc prevents the reduction of aniline during the reaction

  3. zinc reduces the coloured impurities in the aniline and also prevents its oxidation during the reaction

  4. zinc forms the white crystalline complex with aniline

  5. Only (3) and (4)
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This option is correct because acetanilide are formed by the aniline due to the addition of zinc, this reduces the coloured impurities of the aniline and also prevents the oxidation of the reaction.

Multiple choice

What is the similarity between sodium and chlorine?

  1. Both are alkali metals.

  2. Both are halogens.

  3. Both have valency + 1.

  4. Both have 7 valence electrons.

  5. Both form acid on reacting with water.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Yes, it is correct. Valency of both the elements is +1. Sodium on giving one electron, attains stable noble gas structure; 2, 8. If chlorine takes one electron, attains stable noble gas structure; 2, 8, 8.

Multiple choice

Artificial camphor is called

  1. hexachloroethane

  2. chloretone

  3. chloropicrin

  4. chloral

  5. spent lye
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This option is correct because chlorination of propane at 4000C and 74-100 atmospheric pressure forms hexachloroethane in solids. It called artificial comphor.

Multiple choice

Acetamide reacts with halogen and alkaline KOH to give

  1. methyl amine

  2. acetaldehydes

  3. acetic anhydride

  4. acetic acid

  5. dimethyl amine
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This option is correct because acetamide reacts with Br2 and KOH to give methyl amine. This reaction is called hoffmann reaction.

Multiple choice

The pair of compounds salicyldehyde and catechol are synthesised by

  1. duff and tischenko reaction

  2. duff and refomastsky reaction

  3. cannizzaro and refomastsky reaction

  4. tischenko and cannizzaro reaction

  5. duff and dakin reaction
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This option is correct because the duff reaction can also prepare salicylaldehyde by the heating of phenol with hexamethylenetetramine, glycerol and boric acid but an interesting reaction of salicylaldehyde is its oxidation with alkaline hydrogen peroxide to form catechol.

Multiple choice

Acetaldehydes are polymerized in the presence of conc. sulphuric acid to form

  1. metaformaldehydes

  2. paraformaldehydes

  3. paraldehydes

  4. mysitylene

  5. crotonaldehyde
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This option is correct because when the polymerization of acetaldeydes is done in the presence of conc. sulphuric acid, it forms paraldehydes. It gives a pleasant smelling liquid and this is used in medicine as a hypnotic.