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

The presence of nitro group in a benzene ring

  1. activates the ring towards electrophlic substitution

  2. renders the ring basic

  3. deactivates the ring towards nucliophilic substitution

  4. deactivates the ring towards electrophilic substitution

  5. Both (1) and (2)

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This option is correct.

Multiple choice

Which one of the following reactions is favourable at low pressure?

  1. H2 + I2 ⇌ 2HI

  2. PCl5 ⇌ PCl3 + Cl2

  3. N2 + 2H2 ⇌ 2NH3

  4. N2 + O2 ⇌ 2NO
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

  We know that low pressure favours the reaction accompanied with increase in number of moles and in the given option, the number of moles of reactants are less than number of moles of product or we can say there is an increase in number of moles in product side, so this reaction will be favoured at low pressure.

Multiple choice

Study the following reaction carefully and choose the correct answer based on the same.

In the chemical reaction: Ag2O + H2O + 2e- -----> 2Ag + 2OH-

  1. silver is oxidised

  2. silver is reduced

  3. hydrogen is reduced

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 In the given reaction on reactants side, silver is having an oxidation state of +1 in Ag2O and in product side it is having oxidation state of 0 in Ag. Hence, it suffers a change in oxidation state from +1 to 0 which is actually a decrease in oxidation state , hence silver is reduced.

Multiple choice

Plumbo-solvency is represented by the reaction

  1. 2Pb + O2 → 2PbO

  2. Pb + 2HCl → PbCl2 + H2

  3. 2Pb + O2 + 2H2O → 2Pb(OH)2

  4. 2PbS + 3O2 → 2PbO + 2SO2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

 Plumbo-solvency is said to take place when Pb gets converted to its hydroxide on reaction with water in presence of oxygen,  the given option satisfies all the conditions. 

Multiple choice

The reaction of RCH2CH2COOH with red phosphorus in presence of bromine to give R-CH2-CHBr-COOH is called

  1. <span style="font-size:11.0pt;line-height:115%;font-family:"Calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-theme-font:minor-latin;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">Reimer Tiemann reaction

  2. <span style="font-size:11.0pt;line-height:115%;font-family:"Calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-theme-font:minor-latin;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">Cannizaro reaction

  3. <span style="font-size:11.0pt;line-height:115%;font-family:"Calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-theme-font:minor-latin;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">Sandmeyer's reaction

  4. <span style="font-size:11.0pt;line-height:115%;font-family:"Calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-theme-font:minor-latin;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">Hell-Volhard Zelinsky reaction
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Alpha halogenation of carboxylic acid in presence of red phosphorus is called Hell Volhard Zelinsky reaction.

Multiple choice

Urotropine can be obtained by which of the following reactions?

  1. Reaction between formaldehyde and ammonia

  2. Reaction between phenol and formaldehyde

  3. Reaction between vinyl acetylene and hydrochloric acid

  4. Reaction between benzaldehyde and triphenylphosphine alkylindenes

  5. Reaction between acetylene and chlorine
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This option is correct. When formaldehyde and ammonia react with each other, hexamethylene tetramine  is formed. It is called as urotropine.

Multiple choice

'Oil of wintergreen' is obtained when

  1. salicylic acid is treated in the presence of conc. H2SO4/CH3OH

  2. salicylic acid reacts in the presence of C6H5OH/POCl3

  3. salicylic acid is catalysed by (CH3CO)2CO

  4. Both (2) and (3)

  5. phenol is condensed with benzene diazonium chloride

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This option is correct because salicylic acid is treated in the presence of sulphuric acid and methyl alcohol to form methylsalicylates. It is called as oil of wintergreen.

Multiple choice

Mesitylene is formed when

  1. 2 molecules of acetylene react with sulphur

  2. 3 molecules of acetylene are catalysed by red hot tube

  3. 4 molecules of acetylene are catalysed by nickel cyanide under pressure

  4. 3 molecules of propyne are passed through red hot tube

  5. 2 molecules of acetophenone are catalysed in the presence of aluminium tetraoxide
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

This option is correct because three molecules of propyne, when passed through the red hot tube, cyclic polymerisation  takes place,  and forms 1,3,5 trimethylbenzene. It is also known as mesitylene.

Multiple choice

Halogenation of alkanes can be carried out in

  1. dark.

  2. UV light.

  3. diffused sun light.

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

The free radical substitution reaction of alkanes with halogens is initiated by light, typically diffused sunlight, to control the reaction rate.