Chemistry

Chemical Reactions and Equations

684 Questions

Chemical reactions and equations form a foundational chemistry topic where students identify reaction products, balance chemical formulas, and classify reaction types. It covers critical mechanisms like Markovnikov's rule, precipitation, and endothermic or exothermic processes. These questions are highly common in general science sections of state and central government competitive exams.

Endothermic reactionsPrecipitation reactionsDehydrohalogenation of alkyl halidesChemical equation balancingReaction product identification

Chemical Reactions and Equations Questions

Multiple choice general knowledge science & technology

Which of the following is not a first order reaction.

  1. H2O2 => H2O + 0.5 O2

  2. SO2Cl2 => SO2 + Cl2

  3. 2 N2O2 => 4 NO2 + O2

  4. 2 NO2 => 2 NO + O2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Options A (H2O2 decomposition) and B (SO2Cl2 decomposition) are classic first-order reactions. Option D (2NO2 decomposition) is second-order because rate depends on [NO2]². Option C uses an incorrect formula (N2O2 is not stable; should be N2O5 for first-order decomposition), making it the 'not first-order reaction' by being chemically invalid.

Multiple choice general knowledge science & technology

Potassium bromide

  1. KOH

  2. KI

  3. KBr

  4. KCl
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Potassium bromide has the chemical formula KBr, formed from potassium (K) and bromine (Br). It's a salt used historically as an anticonvulsant and sedative. KOH is potassium hydroxide, KI is potassium iodide, and KCl is potassium chloride.

Multiple choice general knowledge science & technology

Potassium bromide

  1. KOH

  2. KI

  3. KBr

  4. KCl
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Potassium bromide has the chemical formula KBr, formed from potassium (K) and bromine (Br). It's a salt used historically as an anticonvulsant and sedative. KOH is potassium hydroxide, KI is potassium iodide, and KCl is potassium chloride.

Multiple choice general knowledge science & technology

Argentous bromide

  1. KOH

  2. HCl

  3. AgBr

  4. KI
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Silver(I) bromide, also called argentous bromide, has the chemical formula AgBr - formed from silver (Ag) and bromine (Br). Like silver chloride, it's a light-sensitive compound used in early photography. KOH is potassium hydroxide, HCl is hydrochloric acid, and KI is potassium iodide.

Multiple choice general knowledge

Oxidation, carbonation, hydrolysis and solution are reactions of

  1. Biological weathering

  2. Chemical weathering

  3. Physical weathering

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Oxidation, carbonation, hydrolysis, and solution are all chemical weathering processes. These involve chemical reactions that break down rocks and minerals through processes like oxygen reacting with minerals (oxidation), carbon dioxide dissolving in water (carbonation), water reacting with minerals (hydrolysis), and minerals dissolving in water (solution). Biological weathering involves living organisms, while physical weathering involves mechanical breakdown.

Multiple choice

Hydrogen acts as an oxidizing agent with

  1. Br2

  2. Na

  3. N2

  4. O3
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

An oxidizing agent gains electrons from another substance in a redox reaction. When hydrogen reacts with sodium (Na), it gains an electron to form H⁺ while Na loses an electron to form Na⁺. Thus hydrogen is reduced (acts as oxidizing agent) and sodium is oxidized. With more electronegative elements like Br₂, N₂, or O₃, hydrogen acts as a reducing agent (loses electrons).

Multiple choice

Benzene reacts with chlorine in the presence of an iron catalyst to produce-

  1. Benzene hexachloride

  2. Benzyl chloride

  3. Chlorobenzene

  4. Benzoyl chloride
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Benzene undergoes electrophilic aromatic substitution with chlorine in the presence of iron(III) chloride catalyst (Fe acts as Lewis acid, FeCl3 is the actual catalyst). This produces chlorobenzene where a chlorine atom substitutes for a hydrogen atom on the benzene ring.

Multiple choice

Which of the following pairs of ‘reagent : corresponding reaction’ is incorrectly matched?

  1. Na metal : Wurtz reaction

  2. Na, C2H5OH, NH3 : Benzoin condensation

  3. H2O2, NaOH : Dakin reaction

  4. ZnCl2, HCl : Lucas reaction

  5. NH2-NH2, NaOH : Wolf-kishner reduction
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The Benzoin condensation is a coupling reaction between two aldehydes that allows the preparation of α-hydroxyketones in the presence of CN- and alcohol. The reagents Na, C2H5OH, NH3 are employed in Birch reduction to reduce conjugation.

Multiple choice

The o- and p- directing groups is/are:

  1. – COCH3
  2. – SO3H
  3. – NR3+
  4. – OCH3
  5. – NO

  1. Only 2

  2. Only 3

  3. Only 4

  4. Both 1 and 3

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

Monosubstituted benzene, when treated with an electrophile, undergoes electrophilic aromatic substitution reaction. Each reaction yields a disubstituted benzene as the product, which can be identified using the descriptors ortho, para and meta as products. Common ortho and para directing groups are:

  • OH, - OCH3, - NR2, - CH3, - NR2 etc. Common meta directing groups are:
  • NO, - SO3H, - COCH3, - CHO, - NO2, - CN, - NR3+ etc. Hence, only –OCH3 group is ortho and para directing.
Multiple choice

The electron transfer from [Fe(H2O)6]2+ to [Fe(H2O)6]3+ is likely to occur via.

  1. d-d transition

  2. inner sphere electron transfer

  3. SN1 mechanism

  4. Outer sphere electron transfer

  5. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This option is correct because in redox reaction, an electron transfer occur through the intact coordination shell of the metal ion. This redox reaction may occur self exchange electron to homonuclear species.

Multiple choice

Which one of the following is correct about Dow process?

  1. Oxidation of toluene to benzoic acid

  2. Reduction of nitrite with bisulphite towards hydroxylamine

  3. Sodium hypochlorite is mixed with three fold excess ammonia at 5oC to give monochloramine

  4. Oxidation of toluene takes place in the presence of air to give phenol

  5. Both (2) and (3) are correct
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This option is correct because oxidation of toluene in the presence of air gives phenol. This process is called the Dow process.