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 acids and alkalis acids with carbonates reactions of acids and bases properties of acids and bases

$Ca(HCO _{3}) _{2} + 2HCl \rightarrow $

  1. $CaCl _{2} + 2H _{2}O + 2CO _{2}$
  2. $2CaCl _{2} + 2H _{2}O + 2CO _{2}$
  3. $CaCl _{2} + 4H _{2}O + 2CO _{2}$
  4. $CaCl _{2} + 2H _{2}O + 4CO _{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$Ca(HCO _{3}) _{2} + 2HCl \rightarrow CaCl _{2} + 2H _{2}O + 2CO _{2}$ 

Metal carbonates react with  acids to give salt, carbon dioxide and water.

Multiple choice chemistry acids and alkalis acids with carbonates reactions of acids and bases properties of acids and bases

Choose the correct option to complete the reaction.
$CaCO _{3}(s) + 2HCl(aq) \rightarrow $

  1. $2CaCl _{2}(aq) + H _{2}O(l) + CO _{2}(g)$
  2. $CaCl _{2}(aq) + 3H _{2}O(l) + CO _{2}(g)$
  3. $2CaCl _{2}(aq) + 4H _{2}O(l) + CO _{2}(g)$
  4. $CaCl _{2}(aq) + H _{2}O(l) + CO _{2}(g)$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$CaCO _{3}(s) + 2HCl(aq) \rightarrow CaCl _{2}(aq) + H _{2}O(l) + CO _{2}(g)$ 

All metal carbonates and hydrogen carbonates react with acids to gives corresponding salt, carbon dioxide and water.

Multiple choice chemistry acids and alkalis acids with carbonates reactions of acids and bases properties of acids and bases

$2HCl{(aq)} + MgCO _{3}(s)\rightarrow$

  1. $MgCl _{2}(aq) + CO _{2}(g) + H _{2}O(l)$
  2. $MgCl _{2}(aq) + CO _{2}(g)$
  3. $MgCl _{2}(aq) + H _{2}O(l)$
  4. $MgCl _{2}(aq) + CO _{2}(g) + 3H _{2}O(l)$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$(A)$  $MgCl _{2}(aq)$ + $CO _{2}(g)$ + $H _{2}O(l)$


$Reaction$ : $2HCl(aq)$ + $MgCO _{3}(s)$ $\rightarrow$ $MgCl _{2}(aq)$ + $CO _{2}(g)$ + $H _{2}O(l)$

Multiple choice chemistry acids and alkalis acids with carbonates reactions of acids and bases properties of acids and bases

$HCl  +  NaHC{O} _{3}\rightarrow$
The given reaction releases which of the following gas?

  1. ${O} _{2}$
  2. $C{O} _{2}$
  3. ${H} _{2}$
  4. ${Cl} _{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Acids react with metal hydrogen carbonates and form corresponding salts, carbon dioxide and water. 
Example:
Hydrochloric acid on reaction with sodium bicarbonate forms sodium chloride, carbon dioxide and water.
$HCl  +  NaHC{O} _{3}  \rightarrow   NaCl  +  C{O} _{2}  +  {H} _{2}O$.

Multiple choice chemistry acids and alkalis acids with carbonates reactions of acids and bases properties of acids and bases

$ 2H _3PO _4 + 3Na _2CO _3 \rightarrow $
What are the products formed?

  1. $2NaPO _4 + 3H _2O + 3CO _2$
  2. $2Na _3PO _4 + 3H _2O + 3CO _2$
  3. $2Na _3PO _4 + H _2O + 3CO _2$
  4. $2Na _3PO _3 + 3H _2O + 3CO _2$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

On adding a carbonate to an acid, effervescence from carbon dioxide gas is released along with the formation of water and salt. $CO _2$ turns lime water milky.
Phosphoric acid + sodium carbonate $\rightarrow$ sodium phosphate + water + carbon dioxide
$ 2H _3PO _4 + 3Na _2CO _3 \rightarrow 2Na _3PO _4 + 3H _2O + 3CO _2 $

Multiple choice chemistry acids and alkalis acids with carbonates reactions of acids and bases properties of acids and bases

Which of the following represents the products obtained when $HCl$ reacts with calcium carbonate?

  1. $CaCl _2$, $H _2O$ and $CO _2$
  2. $CaCl _2$ and $CO _2$
  3. $Ca(OH) _2$ and $CO _2$
  4. $Ca(OH) _2$, $H _2O $ and $CO _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When $HCl$ reacts with calcium carbonate, the products obtained are $CaCl _2$, $H _2O$ and $CO _2$.
$\displaystyle CaCO _3 + 2HCl \rightarrow CaCl _2 + H _2O + CO _2$

Multiple choice chemistry air and atmosphere carbon dioxide - an oxide of carbon component of air - carbon dioxide oxides of non metal

In the following reaction, $O^{18}$ is in what?
$2MnO _4{^-}+5H _2O^{18} _2+6H^+\rightarrow 2Mn^{2+}+8H _2O+5O _2$ 

  1. $H _2O$
  2. $O _2$
  3. Both $(A)$ and $(B)$

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
${ 2MnO } _{ 4 }^{ - }+5{ H } _{ 2 }{ O } _{ 2 }^{ 18 }+6{ H }^{ + }\longrightarrow 2{ Mn }^{ 2+ }+8{ H } _{ 2 }O+5{ O } _{ 2 }$
In the following reaction ${ O }^{ 18 }$ labelled isotope is in ${ O } _{ 2 }$.
Multiple choice chemistry air and atmosphere carbon dioxide - an oxide of carbon component of air - carbon dioxide oxides of non metal

When $H _2S$ burns completely in oxygen, the products include:
(1) S
(2) $SO _2$
(3) $H _2O$

  1. If 1, 2 and 3 are correct

  2. If only 1 and 2 are correct

  3. If only 2 and 3 are correct

  4. If only 1 is correct

  5. If only 3 is correct
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$H _2S$ burns completely in the presence of oxygen as:

${ 2H } _{ 2 }S+{ 3O } _{ 2 }\rightarrow { 2SO } _{ 2 }+2{ H } _{ 2 }O$

Multiple choice chemistry p- block elements-ii compounds of phosphorus- pcl5 phosphorus halides compounds of phosphorus compounds of phosphorus - pcl3

On reaction with $Cl _{2}$, phosphorus forms two types of halides 'A' and 'B'. Halide 'A' is yellowish-white powder but halide 'B' is colourless oily liquid. What would be the hydrolysis products of 'A' and 'B' respectively?

  1. $H _{3}PO _{4}$,$H _{3}PO _{3}$
  2. $HOPO _{3}$, $H _{2}PO _{2}$
  3. $H _{3}PO _{3}$,$H _{3}PO _{4}$
  4. $HPO _{3}$,$H _{3}PO _{3}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$P+Cl _2\longrightarrow \underset {(B)}{PCl _3} +\underset {(A)}{PCl _5}$

$PCl _5+4H _2O\longrightarrow H _3PO _4+5HCl$
$PCl _3+3H _2O\longrightarrow H _3PO _3+3HCl$

Multiple choice chemistry p- block elements-ii compounds of phosphorus- pcl5 phosphorus halides compounds of phosphorus compounds of phosphorus - pcl3

Among the following, the number of compounds that can react with $PCl _{5}$ to give $POCl _{3}$ is: 


$O _{2},\ CO _{2},\ SO _{2},\ H _{2}O,\ H _{2}SO _{4},\ P _{4}O _{10}$

  1. 4

  2. 5

  3. 3

  4. 6
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$PCl$ on reaction with these $4$ compounds produces $POCl _3$:


$PCl _5+SO _2\rightarrow POCl _3+SOCl _2$
$PCl _5+H _2O\rightarrow POCl _3+2HCl$
$PCl _5+H _2SO _4\rightarrow SO _2Cl _2+2POCl _3+2HCl$
$6PCl _5+P _4O _{10}\rightarrow 10POCl _3$.

Multiple choice chemistry p- block elements-ii compounds of phosphorus- pcl5 phosphorus halides compounds of phosphorus compounds of phosphorus - pcl3

Choose the correct options:

  1. PCl$ _5$ (solid) dissociates into PCl$ _4^+$ and PCl$ _6^-$.
  2. LiH reacts with AlH$ _3$ forming LiAlH$ _4$.
  3. $NH _3$ is protonated.
  4. $H _3PO _2$ on heated forms $PH _3$ and $H _3PO _3$.
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation

PCl$ _5$ (solid) dissociates into PCl$ _4^+$ and PCl$ _6^-$. LiH reacts with AlH$ _3$ forming LiAlH$ _4$. These are facts. $NH _3$ is not protonated. On protonation, it forms $NH _4^+$ion. $H _3PO _2$ on heating does not form $PH _3$ and $H _3PO _3$.

Multiple choice chemistry p- block elements-ii compounds of phosphorus- pcl5 phosphorus halides compounds of phosphorus compounds of phosphorus - pcl3

In the given reaction $CI$  replaces one of the H-atoms in $CH _3CH _2OH$. This $H$ is of :


$PCI _5+C\underset{\overline{X}}{H _3}C\underset{\overline{Y}}{H _2}\underset{\overline{Z}}{OH} \longrightarrow$

  1. C (in X)

  2. C (in Y)

  3. O (in Z)

  4. any of X, Y and Z
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In the reaction of ethanol (CH3CH2OH) with PCl5, the hydroxyl group (-OH) is replaced by a chlorine atom. This involves the breaking of the O-H bond (Z position) and the C-O bond.

Multiple choice chemistry p- block elements-ii compounds of phosphorus- pcl5 phosphorus halides compounds of phosphorus compounds of phosphorus - pcl3

In the following reactions :
$(i) P{Cl} _{5}+{SO} _{2}\rightarrow A+B$
$(ii) A+MeCOOH\rightarrow C+{SO} _{2}+HCl$
$(iii) 2C+{Me} _{2}Cd\rightarrow 2D+CD{Cl} _{2}$ The compound (C) is:

  1. $Me-CH -Cl _2$
  2. $Me-CH _2 -Cl$
  3. $Me-\underset { \parallel \\ O }{ C } -Cl$
  4. $Me-C -Cl _3$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$(i) P{Cl} _{5}+{SO} _{2}\rightarrow SO{Cl} _{2} (A)+PO{cl} _{3} (B)$

(ii) $SO{Cl} _{2}+MeCOOH\rightarrow Me-\underset { \parallel \ O }{ C } -Cl (C)+{SO} _{2}+HCl\$