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 chemistry of non-metals oxides of elements simple oxides oxygen

$ZnO+2HCl\longrightarrow  X+{H} _{2}O$
$ZnO+2NaOH\longrightarrow  Y+{H} _{2}O$
Identify $X,Y$ and the nature of $ZnO$ best described by the above reaction

  1. $X=Zn{Cl} _{2}$; $Y=NaZn{O} _{2}$; Nature of $ZnO$- Amphoteric
  2. $X=Zn{Cl} _{2}$; $Y={Na} _{2}Zn{O} _{2}$; Nature of $ZnO$- Amphoteric
  3. $X=Zn{Cl} _{2}$; $Y=NaZn{O} _{2}$; Nature of $ZnO$- Acidic
  4. $X=Zn{Cl} _{3}$; $Y=Zn{OH} _{2}$; Nature of $ZnO$- Basic
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

ZnO reacts with HCl to form ZnCl2 and water, and with NaOH to form Na2ZnO2 (sodium zincate) and water. This dual behavior confirms that ZnO is amphoteric.

Multiple choice chemistry chemistry of non-metals oxides of elements simple oxides oxygen

Which choice or choices demonstrate amphoterism?
i. $HCl + H _{2}O \rightarrow H _{3}O^{+} + Cl^{-}$ and $H _{2}O + N _{3} \rightarrow OH^{-} + NH _{4}^{-}$
ii. $HS^{-} + HCl \rightarrow Cl^{-} + H _{2}S$ and $HS^{-} + NH _{3} \rightarrow NH _{4}^{+} + S^{2-}$
iii. $HCl + NaOH \rightarrow NaCl + H _{2}O$ and $NaCl + H _{2}O \rightarrow HCl + NaOH$

  1. i only

  2. ii only

  3. iii only

  4. i and ii only

  5. i and iii only
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Amphoteric compound or ion is a molecule that cn act as both acid as well as base.

In the first reaction, $H _2O$ acts as both acid and base.It accepts proton and loses proton. Hence. it shows amphoterism.
In the second reaction, ${ HS }^{ - }$ does the same thing.
It accepts and loses proton. 
Hence, both shows amphoterism.

Multiple choice chemistry preparation of gases nitrogen gas component of air - nitrogen nitrogen

Which one of the following pairs is obtained on heating ammonium dichromate?

  1. $N _2$ and $H _2$O
  2. $H _2$O and $H _2$O
  3. $NO _2$ and $H _2$O
  4. NO and $NO _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
On heating ammonium dichromate; $N _2$,$H _2O$ and $Cr _2O _3$ are formed.
 
$(NH _4) _2Cr _2O _7 (s) \longrightarrow N _2 (g) + 4H _2O (g) + Cr _2O _3 (s)  \Delta H = -429 kcal/mol$

Option (A) is correct.
Multiple choice chemistry preparation of gases nitrogen gas component of air - nitrogen nitrogen

The products formed when an aqueous solution of hydrazine reacts with an aqueous alkaline solution of potassium ferricyanide are:

  1. ${K} _{4}[Fe{(CN)} _{6}]$ and ${H} _{2}$.
  2. $4{K} _{4}[Fe{(CN)} _{6}]+4H _2O$ and ${N} _{2}$.
  3. $4{K} _{4}[Fe{(CN)} _{6}]$ and ${H} _{2}$.

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

$4{K} _{3}[Fe{(CN)} _{6}]+4KOH+{N} _{2}{H} _{4}\longrightarrow 4{K} _{4}[Fe{(CN)} _{6}]+4{H} _{2}O+{N} _{2}$.

Hence, the given statement is false.

Multiple choice chemistry preparation of gases nitrogen gas component of air - nitrogen nitrogen

Complete the given reaction :


${(NH _4)} _2Cr _2O _7  \longrightarrow$

  1. $3N _2+ 4H _2O+ 2Cr _2O _3$
  2. $N _2+ 3H _2O+ Cr _2O _3$
  3. $N _2 + 4H _2O+ Cr _2O _3$
  4. $4N _2+ 4H _2O+ Cr _2O _3$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The thermal decomposition of ammonium dichromate is (NH4)2Cr2O7 -> N2 + 4H2O + Cr2O3. This is a classic volcano reaction.

Multiple choice chemistry preparation of gases nitrogen gas component of air - nitrogen nitrogen

$Mg _3N _2 \xrightarrow{H _2O} A(gas) \xrightarrow[\triangle]{CuO} B + C(g) + H _2O$
$C(g)$ can be obtained by heating:

  1. $(NH _4) _2SO _4$
  2. $(NH _4) _2Cr _2O _7$
  3. $NH _4NO _3$
  4. $NH _4Cl$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$Mg _3N _2 \xrightarrow []{3H _2O} \underset {(A)}{2NH _3}+3MgO$

$NH _3 \xrightarrow []{CuO} \underset {(C)}{N _2}(g)+\underset {(B)}{Cu}+H _2O$
$N _2$ will be obtained by decomposition of Ammonium dichromate.
$(NH _4) _2Cr _2O _7 (s) \longrightarrow Cr _2O _3(g)+\underset {(C)}{N _2}+4H _2O$ .

Multiple choice chemistry preparation of gases nitrogen gas component of air - nitrogen nitrogen

In the reaction,

${ \left( { NH } _{ 4 } \right)  } _{ 2 }{ Cr } _{ 2 }{ O } _{ 7 }\xrightarrow [  ]{ \Delta  } { N } _{ 2 }+{ H } _{ 2 }O+{ Cr } _{ 2 }{ O } _{ 3 }$

The coefficient of ${H} _{2}O$ is :

  1. $1$
  2. $2$
  3. $3$
  4. $4$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$ (NH _4) _2Cr _2O _7(s) \rightarrow N _2(g) + 4 H _2O(g) + Cr _2O _3(s)$


To balance the reaction we require 4 moles of $H _2O$.

Hence option D is correct.

Multiple choice chemistry nitrogen and sulfur ammonia-properties and uses ammonia compounds of nitrogen - ammonia

When chlorine reacts with a gas X, an explosive inorganic compound Y is formed. Then X and Y will be :

  1. $\displaystyle X=O _{2}$ and $\displaystyle Y=NCl _{3}$
  2. $\displaystyle X=NH _{3}$ and $\displaystyle Y=NCl _{3}$
  3. $\displaystyle X=O _{2}$ and $\displaystyle Y=NH _{4}Cl$
  4. $\displaystyle X=NH _{3}$ and $\displaystyle Y=NH _{4}Cl$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When $NH _3$ reacts with excess of $Cl$ an explosive substance $NCl _3$ is formed.
$NH _3 + 3Cl _2 \rightarrow NCl _3 + 3HCl$
X is $NH _3$ and Y is $NCl _3$.