Chemistry

Chemical Reactions and Equations

674 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 aluminium patterns and properties of metals chemistry

The dissolution of $Al(OH) _3$ by a solution of NaOH results in the formation of:

  1. $[Al(H _2O) _2(OH) _4]^-$
  2. $[Al(H _2O) _3(OH) _3]^+$
  3. $[Al(H _2O) _4(OH) _2]^+$
  4. $[Al(H _2O) _6(OH) _3]^-$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

1. $[Al(H _2O) _4(OH) _2]^+$

2. $Al(OH) _3$  dissolves in $NaOH$ solution to give $Al(OH)^{-4}$ ion which is supposed to have the octahedral complex species $[Al(OH) _4(H _2O) _2]^-$ in aqueous solution.

3. $Al(OH) _3 + NaOH(aq) \longrightarrow  [Al(OH) _4(H _2O) _2]^-(aq) + NaOH^+(aq)$

Multiple choice aluminium patterns and properties of metals chemistry

In the following reaction sequence,
$(A)+N _2 \xrightarrow { \triangle } (B) \xrightarrow {+H _2O} (C)+(D)$
white ppt. (C) is formed and gas (D) is evolved. White ppt. (C) dissolves in NaOH solution, while gas (D) gives white fumes in HCl. Thus, (A) is :

  1. B

  2. Al

  3. Ga

  4. C
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
$\underset{(A)}{2Al}+N _2 \rightarrow \underset{(B)}{2AlN}$
$\underset{(B)}{AlN}+3H _2O \rightarrow \underset{(C)}{Al(OH) _3}+\underset{(D)}{NH _3}$
Multiple choice aluminium patterns and properties of metals chemistry

$Al {4}C _{3} + 12H _{2}O \rightarrow 3CH _{4} + $______

  1. $4 Al (OH) _{3}$
  2. $4 Al (OH) _{2}$
  3. $3 Al (OH) _{4}$
  4. $3 Al (OH) _{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$ Al _4C _3 + 12H _2O \rightarrow 3CH _4 + 4Al(OH) _3$

When Aluminium carbide $Al _4C _3$ undergoes hydrolysis forms a methane along with a aluminium hydroxide as a product.

Multiple choice carbon tetrachloride ddt preparation of haloalkanes halogen derivatives

The halo compound of methane used as fire extinguisher under the name Pyrene is:

  1. $CHCl _{3}$
  2. $CH _{2}Cl _{2}$
  3. $CCl _{2}F _{2}$
  4. $CCl _{4}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Carbon tetrachloride $CCl _4$, is widely used in fire extinguishers. The liquid vaporized and extinguished the flames by inhibiting the chemical chain reaction of the combustion process.


In 1910, The Pyrene Manufacturing Company of Delaware filed a patent to use carbon tetrachloride to extinguish fires under the name $Pyrene$.

Multiple choice chemistry coordination chemistry bonding in metal carbonyls metal carbonyls coordination compounds

Which of the following is correct?

  1. $H _{3}PO _{3}$ is dibasic and reducing
  2. $H _{3}PO _{3}$ is dibasic and non-reducing
  3. $H _{3}PO _{4}$ is tribasic and reducing
  4. $H _{3}PO _{3}$ is tribasic and non-reducing
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Phosphorous acid, H3PO3, has two P-OH bonds, making it dibasic. It also contains one P-H bond directly linked to hydrogen, which acts as a strong reducing agent.

Multiple choice salts salts and their classification acids, bases and salts chemistry

In the reaction, $BaCl _{2}(aq)+K _{2}SO _{4}(aq)\rightarrow BaSO _4(s)+2KCl(aq)$, which is not a spectator ion?

  1. $K^{+}$
  2. $Cl^{-}$
  3. $Ba^{2+}$ and $SO _{4}^{-2}$
  4. Both $A$ and $B$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Ions that are not involved in the formation of insoluble solid are called as spectator ions.


Therefore, $Ba^{2+}$ and $SO _{4}^{2-}$ ions form insoluble solid.

Hence they are not spectator ions.


Option C is correct.

Multiple choice salts salts and their classification acids, bases and salts chemistry

$Na _2O+2HCl\rightarrow \ ?$

  1. $NaOH+H _2$
  2. $2NaCl+H _2O$
  3. $NaOH+Cl _2$
  4. $2NaCl+O _2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When any element who comes before hydrogen in the reactivity series reacts with a compound containing hydrogen, it displaces the hydrogen from the compound, since it's reactivity is more than that of hydrogen.

Here, $Na _2O$ is a basic metal oxide containing Na which is more reactive than the Hydrogen present in the acid $HCl$ and thus the Na replaces hydrogen from the acid, leading to the formation of salt and water.
Salt and water are formed because the reaction takes place between acidic and basic species.
$Na _2O+2HCl \rightarrow 2NaCl+H _2O$
Hence, the correct answer is option (B).

Multiple choice salts salts and their classification acids, bases and salts chemistry

Complete the given reaction:

$CaCl _2+Na _2CO _3 \longrightarrow$

  1. $CaCO _3+NaCl$
  2. $CaCO _3+2NaCl$
  3. $CaO+NaCl$

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

Calcium chloride react with sodium carbonate to produce calcium carbonate and sodium chloride.
CaCl2 + Na2CO3 → CaCO3 + 2NaCl

Multiple choice salts salts and their classification acids, bases and salts chemistry

What are the products of the following reaction? 

$\displaystyle { H } _{ 2 }{ SO } _{ 4 }\left( aq \right) +{ Ba\left( OH \right)  } _{ 2 }\rightarrow $

  1. $\displaystyle { O } _{ 2 }$
  2. $\displaystyle Ba{ SO } _{ 4 }$
  3. $\displaystyle { O } _{ 2 }$ and $\displaystyle Ba{ SO } _{ 4 }$
  4. $\displaystyle { H } _{ 2 }O$ and $\displaystyle Ba{ SO } _{ 4 }$

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

The products of the  reaction between barium hydroxide and sulphuric acid are barium sulphate and water.
$\displaystyle { H } _{ 2 }{ SO } _{ 4 }\left( aq \right) +{ Ba\left( OH \right)  } _{ 2 }\rightarrow \displaystyle Ba{ SO } _{ 4 } + \displaystyle { H } _{ 2 }O    $
It is acid base neutralisation reaction to form salt and water.

Multiple choice salts salts and their classification acids, bases and salts chemistry

Among the following reactions, find the one which gives precipitation?

  1. $\displaystyle { Ag }^{ + }\left( aq \right) +{ Cl }^{ - }\rightarrow AgCl\left( s \right) $
  2. $\displaystyle { C } _{ 5 }{ H } _{ 12 }\left( s \right) +8{ O } _{ 2 }\left( g \right) \rightarrow 5{ CO } _{ 2 }\left( g \right) +6{ H } _{ 2 }O\left( l \right) $
  3. $\displaystyle { NH } _{ 3 }\left( s \right) +{ H } _{ 2 }O\left( s \right) \leftrightharpoons { NH } _{ 4 }^{ + }\left( s \right) +{ OH }^{ - }\left( s \right) $
  4. $\displaystyle H{ C } _{ 2 }{ H } _{ 3 }{ O } _{ 2 }\left( l \right) +{ OH }^{ - }\left( aq \right) \rightarrow { H } _{ 2 }O\left( l \right) +{ C } _{ 2 }{ H } _{ 3 }{ O } _{ 2 }^{ - }\left( aq \right) $
  5. $\displaystyle Ca{ CO } _{ 3 }\left( s \right) \rightarrow CaO\left( s \right) +Ca{ O } _{ 2 }\left( g \right) $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$A.$ Precipitation reaction
A precipitate of $AgCl$ is formed.
$\displaystyle { Ag }^{ + }\left( aq \right) +{ Cl }^{ - }\rightarrow AgCl\left( s \right) $
$B.$ Combustion reaction
$C.$ Hydrolysis
$D.$ Acid-base neutralization-Acetic acid is neutralized by hydroxide base.
$E.$ Decomposition reaction

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

$Mg _2C _3$ reacts with water to form propyne. $C _3^{4-}$ has:

  1. two sigma and two pi bonds

  2. three sigma and one pi bonds

  3. two sigma and one pi bonds

  4. two sigma and three pi bonds
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

${ Mg } _{ 2 }{ C } _{ 3 }+{ 4H } _{ 2 }O\longrightarrow { Mg(OH) } _{ 2 }+{ C } _{ 3 }{ H } _{ 4 }$ Propyne
$ { C } _{ 3 }^{ 4- }  ion $

$\left[ C\equiv C-C \right] ^{ 4- }$
$2 \, \Pi $ Bonds
$2\,\sigma$ Bonds

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

$Mg _{2}C _{3}$ reacts with water forming propyne, $C _{2}^{4-}$ has

  1. Two sigma and two pi bonds

  2. Three sigma and one pi bonds

  3. Two sigma and one pi bonds

  4. Two sigma and three pi bonds
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The C3(4-) ion is the propynide ion, which has the structure C-C=C. It contains two sigma bonds and two pi bonds.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

Select correct statements about $C^{4-} _3$ ion.

  1. It reacts with $H _2O$ forming $C _3H _6$.
  2. It reacts with $H _2O$ forming $C _3H _4$.

  3. It has two sigma and two pi bonds.

  4. It has three sigma and one pi bonds.
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

The correct statements about $C^{4-} _3$ ion are

(B) It reacts with $H _2O$ forming $C _3H _4$

$\displaystyle  C^{4-} _3 + 2H _2O \rightarrow C _3H _4+O _2 + 4e^-$

(C) It has two sigma and two pi bonds $\displaystyle [C=C=C]^{4-} $

Multiple choice chemistry enthalpy changes enthalpy changes and enthalpy profile diagrams enthalpy study of enthalpy

Two reactions are given below:

(i) $CO _{(g)} + \frac{1}{2}O _2{(g)} \rightarrow CO _2{(g)}$

(ii) $ Ag _2O _{(s)} \rightarrow 2Ag _{(s)} + \frac{1}{2}O _2{(g)}$

Which of the following statements is true?

  1. For (i) $\vartriangle$H < $\vartriangle$E and for (ii) $\vartriangle$H > $\vartriangle$E
  2. For (i) $\vartriangle$H > $\vartriangle$E and for (ii) $\vartriangle$H < $\vartriangle$E
  3. For both (i) and (ii) $\vartriangle$H > $\vartriangle$E
  4. For both (i) and (ii) $\vartriangle$H < $\vartriangle$E
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\Delta H=\Delta E+\Delta { n } _{ g }RT$ 


(i) $CO(g) + \cfrac { 1 }{ 2 } { O } _{ 2 }(g) \longrightarrow  C{ O } _{ 2 }(g)$

$ \quad   \Delta { n } _{ g }=1-\cfrac { 1 }{ 2 } -1=-\cfrac { 1 }{ 2 } <0$

$\therefore \Delta H<\Delta E$

(ii) ${ Ag } _{ 2 }O(s) \longrightarrow  2Ag(s) + \cfrac { 1 }{ 2 } { O } _{ 2 }(g)$

$\quad  \Delta { n } _{ g }=\cfrac { 1 }{ 2 } +0-0=\cfrac { 1 }{ 2 } >0$ 

$\therefore \Delta H>\Delta E$

So, the correct option is A.