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 hydrogen and its compounds heavy water study of heavy water hard water and soft water

$ \displaystyle 4{ D } _{ 2 }O+3Fe \xrightarrow[]{red-hot} Fe _{3}O _{4}+gas.$ The gas produced in the above reaction is:

  1. $ \displaystyle O _{2}$
  2. $ \displaystyle H _{2}$
  3. $ \displaystyle D _{2}$

  4. none
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Reaction:

$ \displaystyle 4{ D } _{ 2 }O+3Fe \xrightarrow[]{red-hot} Fe _{3}O _{4}+ D _2$. The gas produced in the reaction is deuterium.

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

Which one of the following reactions does not occur?

  1. ${ F } _{ 2 }+2{ Cl }^{ - }\rightarrow 2{ F }^{ - }+{ Cl } _{ 2 }$
  2. ${ Cl } _{ 2 }+2{ F }^{ - }\rightarrow 2{ Cl }^{ - }+{ F } _{ 2 }$
  3. ${ Br } _{ 2 }+2{ I }^{ - }\rightarrow 2{ Br }^{ - }+{ I } _{ 2 }$
  4. ${ Cl } _{ 2 }+2{ Br }^{ - }\rightarrow 2Cl^-+{ Br } _{ 2 }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

With progressive increase in atomic number, the reduction potential of halogens decreases, thus oxidising power also decreases. Hence, a halogen with lower atomic number will oxidise the halide ion of higher atomic number and therefore, will liberate them from their salt solution.
Hence, the reaction
${ Cl } _{ 2 }+2{ F }^{ - }\rightarrow 2{ Cl }^{ - }+{ F } _{ 2 }$
is not possible.

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

X, Y, Z are three elements which undergo chemical changes according to the following equations:
$I:\, X _2O _3 + 2Y \rightarrow Y _2O _3 + 2X$
$II:\, Y _2O _3 + 3Z \rightarrow 3ZO + 2Y$
The order of increasing reactivity is:

  1. X < Y < Z

  2. Y < X < Z

  3. Z < X < Y

  4. Z < Y < X
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Y has displaced X in reaction I. So, Y is more reactive than X.
Z has displaced Y is reaction II. So, Z is more reactive than Y. 

Thus, Z is most reactive and X is the least reactive.

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

In the reaction between $Al$ and $Fe _2O _3$, what is the correct final reaction?

  1. $Al+Fe _2O _3 \rightarrow Al _3O _2+2Fe$
  2. $2Al+Fe _2O _3 \rightarrow Al _2O _3+2Fe$
  3. $Al+Fe _2O _3 \rightarrow Al _2O _3+Fe _2$
  4. $Al+Fe _2O _3 \rightarrow Al _2O _3+2Fe$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Al will displace iron from solution.
$\displaystyle  2Al+Fe _2O _3 \rightarrow Al _2O _3+2Fe$

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

$Li$, $K$, $Ca$, $Na$, $Mg$, $Al$, $Zn$, $Fe$, $Pb$, $Cu$, $Hg$, $Ag$
$I$. The reaction $3Fe(s)+2Al{({NO} _{3})} _{3}(aq)\rightarrow 2Al(s)+3Fe{({NO} _{3})} _{2}(aq)$ will occur.
$II$. Iron is higher on the activity series than aluminum.

  1. Statement $I$ is true, Statement $II$ is true and is a correct explanation of the phenomena described in $I$
  2. Statement $I$ is true, Statement $II$ is false
  3. Statement $I$ is false, Statement $II$ is true
  4. Statement $I$ is false, Statement $II$ is false
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

By using the reactivity series of metals, one can predict the products of displacement reactions . Each element in the reactivity series can be replaced from a compound by any of the elements above it. For ex: $Mg$ can replace $Zn$ from the solution. 

$Al$ is higher on the activity series than $Fe$.
Therefore $Fe$ can not displace $Al$ from $Al{(NO _3)} _3$
$\therefore 3Fe+2Al{(NO _3)} _3\longrightarrow 2Al+3Fe{(NO _3)} _2$ will not occur.

Multiple choice chemistry reactivity series and electrochemistry reactivity series and displacement reactions chemical properties of metals chemical properties of metals and non metals

To what type of reaction does the activity series apply?

  1. Synthesis

  2. Single replacement

  3. Double replacement

  4. Decomposition
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

An activity series is a list of substances ranked in order of relative reactivity. For example, magnesium metal can knock hydrogen ions out of solution, so it is considered more reactive than elemental hydrogen.

Multiple choice chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

Identify the correct representation of reaction occurring during chloro-alkali process. 

  1. $2NaCl(l)+ 2H _2O(l) \rightarrow 2NaOH(l) + Cl _2(g) + H _2(g)$
  2. $2NaCl(s)+ 2H _2O(aq) \rightarrow 2NaOH(aq) + Cl _2(g) + H _2(g)$
  3. $2NaCl(aq)+ 2H _2O(l) \rightarrow 2NaOH(aq) + Cl _2(aq) + H _2(aq)$
  4. $2NaCl(aq)+ 2H _2O(l) \rightarrow 2NaOH(aq) + Cl _2(g) + H _2(g)$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Chloro-alkali process is an industrial process for the electrolysis of sodium chloride. It is used to produce chlorine and sodium hydroxide. Aqueous sodium chloride or brine ina membrane cell.


At cathode: ${ 2H } _{ 2 }O+2{ e }^{ - }\rightarrow { H } _{ 2 }+{ 2OH }^{ - }$ 

At anode: $2{ Cl }^{ - }\rightarrow { Cl } _{ 2 }+2{ e }^{ - }$ 


$2NaCl(aq)+2{ H } _{ 2 }O\rightarrow { Cl } _{ 2 }(g)+{ H } _{ 2 }(g)+2NaOH(aq)$


Option $(D)$ suggests the correct reaction.

Multiple choice chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

$Na _2CO _3.10H _2O \longrightarrow Na _2CO _3.H _2O$

The given reaction is an example of:

  1. efflorescent substance

  2. deliquescent substance

  3. hygroscopic substance

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

In this reaction water is being released. This type of substance is known as efflorescent substance.

Multiple choice chemistry water drying and dehydrating agents hydrolysis of salts and the ph of their solutions chemical equilibrium and acids-bases

Identify the correct representation of reaction occurring during chloralkali process.

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

Sodium chloride in water is a brine solution which gives sodium hydroxide in aqueous solution and hydrogen and chlorine gases. It is known as chloralkali process. It is an industrial process for the electyrolysis of sodium chloride. It is the technology which is used to produce chlorine and caustic soda(sodium hydroxide) on commercial scale.

Multiple choice botany photosynthesis modern concept of photosynthesis photosystems photosynthesis in higher plants

Hill reaction takes place

  1. In the absence of ${CO _2}$

  2. In the presence of carbon dioxide

  3. In the absence of a suitable electron acceptor

  4. None of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Robin Hill in the year 1939 showed that all chloroplasts extracted from leaves of Stellaria media and Lamium album are suspended in a test tube containing suitable electron acceptor, e.g., potassium ferrioxalate and potassium ferricyanide, oxygen is released due to the photochemical splitting of water. Under these conditions, no CO$ _2$ is consumed and no carbohydrate is produced.

So the correct option is 'None of the above'.