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 chemistry amines chemical reactions of diazonium salts chemical properties of diazonium salts diazonium salts

3- Amino-2, 3-dimethyl butan-2-ol when treated with $ NaNO _{2}/HCl$ gives product (X). (X) on treatment with $LiAlH _{4}$ forms (Y). (Y) on heating with $conc. H _{2}SO _{4}$ forms (Z). The molecular weight of (Z) is :

  1. 81

  2. 82

  3. 83

  4. 84
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

3- Amino-2, 3-dimethyl butan-2-ol is diazotized with sodium nitrite in presence of HCl at low temperature to obtain 3,3-dimethylbutan-2-one (compound X).
The carbonyl group is then reduced to obtain 3,3-dimethylbutan-2-ol (compound Y). This is followed by dehydration to obtain 2,3-dimethylbut-2-ene (compound Z).

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

When aluminium hydroxide is reacted with excess sodium hydroxide, the soluble amphoteric compound is formed. Mark the correct formula. 

  1. $\displaystyle { \left[ { Al\left( OH \right) } _{ 4 } \right] }^{ - }$
  2. $\displaystyle { \left[ { Al\left( OH \right) } _{ 5 } \right] }^{ 2- }$
  3. $\displaystyle { \left[ { Al\left( OH \right) } _{ 6 } \right] }^{ 3- }$
  4. $\displaystyle { \left[ { Al\left( OH \right) } _{ 7 } \right] }^{ 4- }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$Al(OH) _3 + NaOH \rightarrow Na^+ [Al(OH) _4]^-$

 Aluminium hydroxide when reacted with excess sodium hydroxide, the soluble amphoteric compound  formed is sodium tetra hydroxoaluminate (III).

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

When aluminium hydroxide is reacted with excess ammonium hydroxide, the insoluble compound is formed. Mark the correct formula.

  1. $\displaystyle { \left[ { Al\left( OH \right) } _{ 4 } \right] }^{ 1- }$
  2. $\displaystyle { \left[ { Al\left( OH \right) } _{ 5 } \right] }^{ 2- }$
  3. $\displaystyle { \left[ { Al\left( OH \right) } _{ 6 } \right] }^{ 3- }$
  4. $\displaystyle { \left[ { Al\left( OH \right) } _{ 7 } \right] }^{ 4- }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Aluminium hydroxide reacts with excess hydroxide ions to form the soluble tetrahydroxoaluminate complex, [Al(OH)4]-. However, in some contexts, the hexahydroxoaluminate complex [Al(OH)6]3- is also discussed in coordination chemistry.

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

Which of the following equation represents action of alkali on oxide?

  1. $ZnO+2NaOH\rightarrow Na _2ZnO _2+H _2O$
  2. $Zn\begin{pmatrix}OH\end{pmatrix} _2+2NaOH\rightarrow NaZnO _2+2H _2O$
  3. $PbO+2NaOH\rightarrow Na _2PbO _2+2H _2O$

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

Oxides of certain metals react with acid and alkali to give salt and water.
$ZnO+2NaOH\rightarrow Na _2ZnO _2+H _2O$ is the only correct equation.

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

Which of the following equation represents action of alkali on hydroxide?

  1. $ZnO+2NaOH\rightarrow Na _2ZnO _2+H _2O$
  2. $Zn\begin{pmatrix}OH\end{pmatrix} _2+2NaOH\rightarrow Na _2ZnO _2+2H _2O$
  3. $PbO+2NaOH\rightarrow Na _2PbO _2+2H _2O$

  4. Both A and C
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$Zn\begin{pmatrix}OH\end{pmatrix} _2+2NaOH\rightarrow Na _2ZnO _2+2H _2O$ represents action of alkali on hydroxide.

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

Which of the following equation represents action of alkali on aluminium hydroxide?

  1. $Al\begin{pmatrix}OH\end{pmatrix} _3+NaOH\rightarrow NaAlO _2+2H _2O$
  2. $Al\begin{pmatrix}OH\end{pmatrix} _3+2KOH\rightarrow2KAlO _2+H _2O$
  3. $Al\begin{pmatrix}OH\end{pmatrix} _3+KOH\rightarrow KAlO _2+2H _2O$

  4. Both A and C
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Aluminium hydroxide reacts with sodium hydroxide or potassium hydroxide to form the corresponding aluminate. Both Al(OH)3 + NaOH -> NaAlO2 + 2H2O and Al(OH)3 + KOH -> KAlO2 + 2H2O are valid representations of this reaction.

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

Complete the following equation
$Pb\begin{pmatrix}OH\end{pmatrix} _2+NaOH\rightarrow$

  1. $Pb\begin{pmatrix}OH\end{pmatrix} _2+2NaOH\rightarrow Na _2PbO _2+2H _2O$
  2. $Pb\begin{pmatrix}OH\end{pmatrix} _2+NaOH\rightarrow2Na _2PbO _2+H _2O$
  3. $Pb\begin{pmatrix}OH\end{pmatrix} _2+2NaOH\rightarrow Na _2PbO _2+H _2O$
  4. $Pb\begin{pmatrix}OH\end{pmatrix} _2+NaOH\rightarrow Na _2PbO _2+2H _2O$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$Pb\begin{pmatrix}OH\end{pmatrix} _2+2NaOH\rightarrow Na _2PbO _2+2H _2O$

Multiple choice action of alkalis on some metals and metal oxides analytical chemistry properties of acids and bases acids, bases and salts chemistry

Chromium hydroxide on reaction with excess $\displaystyle NaOH$ gives a soluble compound. Guess the molecular formula.

  1. $\displaystyle \left[ { Cr\left( OH \right) } _{ 3 } \right] $
  2. $\displaystyle { \left[ { Cr\left( OH \right) } _{ 4 } \right] }^{ - }$
  3. $\displaystyle { \left[ { Cr\left( OH \right) } _{ 5 } \right] }^{ 2- }$
  4. $\displaystyle { \left[ { Cr\left( OH \right) } _{ 6 } \right] }^{ 3- }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

An excess of sodium hydroxide solution is added to a solution of the hexaaquachromium(III) ions to produce a solution of green hexahydroxochromate(III) ions.

$[Cr(H _2O) _6]^{3+} \xrightarrow{NaOH} [Cr(H _2O) _3(OH) _3] \xrightarrow{excess NaOH} [Cr(OH) _6]^{-3}$

Multiple choice chemistry study of the first element - hydrogen occurrence of hydrogen introduction to hydrogen hydrogen

Following reaction is called __________ reaction.
$CO (g)\ +\ H _2O (g) \xrightarrow [catalyst]{673} CO _2(g)\ +\ H _2(g)$

  1. combustion

  2. disproportionate

  3. coal gasification

  4. water-gas shift
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The water-gas shift reaction (WGSR) describes the reaction of carbon monoxide and water vapor to form carbon dioxide and hydrogen (the mixture of carbon monoxide and hydrogen is known as water gas):

$CO+{ H } _{ 2 }O\rightleftharpoons C{ O } _{ 2 }+{ H } _{ 2 }$

Multiple choice chemistry study of the first element - hydrogen occurrence of hydrogen introduction to hydrogen hydrogen

Which of the following reactions is an example of a use of water gas in the synthesis of other compounds?

  1. $CH _4(g) +\ H _2O(g) \xrightarrow[Ni]{1270 K} CO(g) +\ 3H _2(g)$
  2. $CO(g) +\ H _2O(g) \xrightarrow[Catalyst]{673 K} CO _2(g) +\ H _2(g)$
  3. $CnH _{2n+2}(g) +\ nH _2O(g) \xrightarrow[Ni]{1270 K} nCO(g) +\ (2n+1)H _2(g)$
  4. $CO(g) +\ 2H _2(g) \xrightarrow[Catalyst]{Cobalt} CH _3OH(l)$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Carbon monoxide and hydrogen react over a catalyst to produce methanol. Today, the most widely used catalyst is a mixture of copper and zinc oxides, supported on alumina, as first used by ICI in 1966. At 5–10 MPa (50–100 atm) and 250 °C (482 °F), the reaction is characterized by high selectivity (>99.8%): 

$\\ CO+2{ H } _{ 2 }→C{ H } _{ 3 }OH$

Multiple choice chemistry hydroxy compounds and ethers chemical properties of ethers ethers alcohols, phenols and ethers

An organic compound with molecular formula $C _4H _{10}O$ does not react with sodium . With excess of HI it gives only one type of alkyl halide. The compound is:

  1. $C _2H _5OC _2H _5$
  2. $CH _3{\underset{OCH _3}{\underset{|}{C}}}HCH _3$
  3. $CH _3CH _2CH _2OCH _3$
  4. $CH _3CH _2CH _2CH _2OH$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$C _4H _{10}O$ can have two structures :


$CH _3CH _2CH _2CH _2OH$   and  $C _2H _5OC _2H _5$.

Since it does not react with Na metal, it can not be an alcohol.

$C _2H _5OC _2H _5 + \underset{excess}HI\rightarrow 2C _2H _5I + H _2O$

Multiple choice chemistry hydroxy compounds and ethers chemical properties of ethers ethers alcohols, phenols and ethers

Which of the following products are not correctly matched in the given reactions?

  1. $C _2H _5OCH _3 + HBr \xrightarrow{373K} C _2H _5OH + CH _3Br$
  2. $C _2H _5OC _2H _5 + 2HI \rightarrow C _2H5I + C _2H _5OH$
  3. $C _2H _5OC _2H _5 + \overset{Excess}{HCl} \xrightarrow{Cold} [(C _2H _5) _2O^+H]Cl^-$
  4. $(CH _3) _3COC _2H _5 \xrightarrow{HI} (CH _3) _3CI + C _2H _5OH$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$C _2H _5-O-C _2H _5 +\underset{(excess)} 2HI \rightarrow 2C _2H _5I + H _2O$

Multiple choice chemistry hydroxy compounds and ethers chemical properties of ethers ethers alcohols, phenols and ethers

Anisole on reaction with chloromethane in presence of anhydrous $AlCl 3$ gives __________.

  1. o-methyl anisole and p-methoxy anisole

  2. p-methyl anisole and p-methoxy anisole

  3. o-methyl anisole and p-methyl anisole

  4. o-methoxy acetphenone and p-methoxy acetophenone .
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Anisole i.e. Phenyl methyl ether $CH _3OC _6H _5$ reaction with Chloromethane in the presence of anhy $AlCl _3$ electrophilic substitution reaction at ortho and para position w.r.t. methoxy group on benzene ring. It is called Friedel-craft alkylation reaction and represented as:
$C _6H _5OCH _3+ CH _3Cl \overset {AlCl _3}{\rightarrow} o-CH _3C _6H _5OCH _3+p-CH _3C _6H _5OCH _3$
Hence Anisole on reaction with chloromethane in presence of anhydrous AlCl3 gives o-methyl anisole and p-methyl anisole