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 the p-block elements - group 13 study of orthoboric acid some important compounds of boron study of boron

$H _{3}BO _{3}\overset{T _{1}}{\rightarrow}X\overset{T _{2}}{\rightarrow}Y\overset{red:hot}{\rightarrow}B _{2}O _{2}$


 if $T _{1}< T _{2}$ then X and Y respectively are-

  1. $X=$ Metaboric acid and $Y=$ Tetraboric acid
  2. $X=$ Tetraboric acid and $Y=$ Metaboric acid
  3. $X=$ Borax and $Y=$ Metaboric acid
  4. $X=$ Tetraboric acid and $Y=$ Borax
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Effect of temperature at $100^{\circ}C \,,\,H _{3}BO _{3}$ losses water and convert into metaboric acid.

$H _{3}BO _{3}\xrightarrow{100^{\circ}C}HBO _{2}+H _{2}O$

metaboric acid form tetraboric acid on heating at $160^{\circ}C$

$4HBO _{2}\xrightarrow{160^{\circ}C}H _{2}B _{4}O _{7}+H _{2}O$

On strong heating, $B _{2}O _{3}$ is produced

$H _{2}B _{4}O _{7}\rightarrow 2B _{2}O _{3}+H _{2}O$

Hence, option $A$ is correct.
Multiple choice chemistry the p-block elements - group 13 study of orthoboric acid some important compounds of boron study of boron

Which of the following compounds are formed when $BCl _3$ is treated with water?

  1. $H _3BO _3$
  2. $B _2H _6$
  3. $B _2O _3$
  4. $HBO _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
$B{Cl} _3$ hydrolyzes readily to give hydrochloric acid and boric acid.

$B{Cl} _3 + 3H _2O \; \xrightarrow{hydrolyzes} \; B{(OH)} _3 + 3HCl$

Hence, the correct answer is option $\text{A}$.
Multiple choice chemistry the p-block elements - group 13 study of orthoboric acid some important compounds of boron study of boron

The reaction,

$B(OH) _3+NaOH\rightarrow Na[B(OH) _4]$ can be made to proceed in forward direction by :

  1. adding cis-1, 2-diol.

  2. adding borax.

  3. adding trans-1, 2-diol.
  4. adding $Na _2HPO _4$.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
If polyhydroxy compound like glycerol, mannitol or sugar are added to titration mixture than it can be titrated with $NaOH$.

Due to formation of chelated complex, the reaction moves in forward direction.

$B(OH) _{3}+NaOH\rightarrow Na[B(OH) _{4}]$
Multiple choice chemistry the p-block elements - group 13 study of orthoboric acid some important compounds of boron study of boron

$B _{2}Ca _{6}O _{11}+ Na _{2}CO _{3}\overset{\Delta }{\rightarrow}\left [ X \right ]+CaCO _{3}+NaBO _{2}$ (unbalanced equation)
Correct choice(s) for [X] is/are:

  1. structure of anion of crystalline [X] has one boron atom sp$^{3}$ hybridised and other three boron atoms sp$^{2}$
    hybridised

  2. X with NaOH (aq.) gives a compound which on reaction with hydrogen peroxide in alkaline medium yields
    a compound used as brightner in soaps
  3. hydrolysis of [X] with HCl or H$ _{2}$SO$ _{4}$ yields a compound which on reaction with HF gives fluoroboric acid

  4. [X] on heating with chromium salts in oxidising flame gives green coloured bead in cold
Reveal answer Fill a bubble to check yourself
B,C,D Correct answer
Explanation

Compound [X] is Na$ _{2}$B$ _{4}$O$ _{7}$
(A) two boron atoms are $sp^{2}$ while other two boron atoms are $sp^{3}$ hybridised.
(B) product is sodium peroxoborate which is used as brightner in soaps.
(C) $H _{3}BO _{3}$ is formed which with HF gives $HBF _{4}$.
(D) Green bead in oxidising as well as in reducing flame in cold.

Multiple choice chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

Identify the process to which the following reaction belongs : 


$\displaystyle { Al } _{ 2 }{ O } _{ 3 }.{ 2H } _{ 2 }O+{ Na } _{ 2 }{ CO } _{ 3 }\longrightarrow { 2NaAlO } _{ 2 }+{ 2H } _{ 2 }O+{ CO } _{ 2 }$

$\displaystyle { 2NaAlO } _{ 2 }+{ 2H } _{ 2 }O+{ CO } _{ 2 } \underrightarrow { 50-{ 60 }^{ o }C } { Al } _{ 2 }{ O } _{ 3 }.{ 2H } _{ 2 }O+{ Na } _{ 2 }{ CO } _{ 3 }$

  1. Hall's process

  2. Baeyer's process

  3. Serpeck's process

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Hall's Process: (Red bauxite)

Bauxite one + $Na _2CO _3 \xrightarrow{Fused} NaAlO _2$
                                                          $\downarrow $ extracted with water
                                                    Solution
                                                          $\downarrow$ warmed $50^o - 60^oC$
                                                   $CO _2$ is circulated
                                                          $\downarrow$
                                                   $Al(OH) _3 + Na _2CO _3$

Multiple choice chemistry substances in common use preparation, properties and uses of baking soda chemical from common salt compounds of carbon

${NaHCO _3+?\rightarrow NaCl+CO _2+H _2O}$ :

  1. ${H NO _3}$
  2. $HCl$
  3. ${Cl _2}$
  4. ${H _2SO _4}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When sodium bicarbonate reacts with $HCl$, chlorine binds with sodium and forms sodium chloride and bicarbonate ion binds with hydrogen ion of $HCl$ and forms carbonic acid. The carbonic acid further dissociates to water and carbon dioxide.

Multiple choice chemistry nature of matter heterogenous mixture - colloidal solution and its properties suspensions and colloids mixtures

Which reaction gives colloidal solution

  1. $2Cu+{Cl} _{2}\rightarrow {Cu} _{2}{Cl} _{2}$
  2. $2H{NO} _{3}+3{H} _{2}S\rightarrow 3S+4{H} _{2}O+2NO$
  3. $2Mg+{CO} _{2}\rightarrow 2MgO+C$
  4. $2Cu+{O} _{2}\rightarrow 2CuO$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The reaction 2HNO3 + 3H2S -> 3S + 4H2O + 2NO produces colloidal sulfur (S) in water, which is a classic example of preparing a colloidal solution via chemical reaction.

Multiple choice chemistry nature of matter heterogenous mixture - colloidal solution and its properties suspensions and colloids mixtures

Out of the following, which reaction gives a colloidal solution?

  1. $Cu + HgCl _{2}\rightarrow CuCl _{2} + Hg$
  2. $2HNO _{3} + 3H _{2}S\rightarrow 3S + 4H _{2}O + 2NO$
  3. $2Mg + CO _{2} \rightarrow 2MgO + C$
  4. $Cu + CuCl _{2}\xrightarrow {\text {in presence of excess of HCl}} Cu _{2}Cl _{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Similar to the previous question, the reaction of hydrogen sulfide with nitric acid produces sulfur, which forms a colloidal sol.

Multiple choice chemistry substances in common use chemical from common salt compounds of carbon some useful compounds in everyday life

Which one of the following processes does not occur during formation of $CH{ Cl } _{ 3 }$ from ${ C H } _{ 3 }OH$ and bleaching powder ?

  1. Hydrolysis

  2. Oxidation

  3. Reduction

  4. Chlorination
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
The process that does not occur during the formation of $CHCl _3$ from $CH _3OH$ and Bleaching Powder is REDUCTION PROCESS.
In $CHCl _3$ oxidation state of carbon is +2 and in methanol oxidation state of carbon is-2. This is reduction.
Multiple choice chemistry endothermic and exothermic reactions endothermic reactions what are enthalpy changes energy change in chemical reactions

Which of the following is the most exothermic reaction?

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

Option B is the correct answer.

The reaction written in option B is a combustion reaction. It is combustion of Propane. Combustion reactions are exothermic in nature.
Thus, combustion of propane is an exothermic reaction and a lot of heat is generated, which causes more propane to combine with Oxygen.