Chemistry

Chemical Reactions and Processes

571 Questions

Chemical reactions and processes questions cover the transformation of substances through electrolysis, thermal decomposition, and catalysis. Key areas include identifying gas evolution, balancing chemical equations, and understanding industrial chemical applications. This general chemistry topic is a staple in the science sections of multiple competitive examinations.

Thermal decompositionElectrolysis processGas evolution reactionsHeterogeneous catalystsFuel cell components

Chemical Reactions and Processes Questions

Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

If aq. NaCl is electrolysed using graphite as anode and Hg as cathode than products are:

  1. $\displaystyle Cl _{2}$ gas at anode and Na at cathode
  2. $\displaystyle Cl _{2}$ gas at anode and $\displaystyle H _{2}$ gas at cathode
  3. $\displaystyle O _{2}$ gas at anode and $\displaystyle H _{2}$ gas at cathode
  4. $\displaystyle Cl _{2}$ gas at anode and $\displaystyle O _{2}$ gas at cathode
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If aq. $NaCl$ is electrolyzed using graphite as anode and $Hg$ as cathode then products are $Cl _2$ gas at anode and $Na$ at the cathode.

In the presence  of Hg electrode the over voltage of $H _2$ is very high and reduction of $H _2O$ is possible.

Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis
Which of the following will not produce an electrolytic solution upon addition of water?
  1. $N _2(g)$
  2. $HCl(g)$
  3. $KOH(s)$
  4. $NaI(s)$
  5. $CaCl _2(s)$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When water is added, HCl, KOH, NaI and $CaCl _2$ will produce an electrolytic solution. However, $N _2$ will not produce an electrolytic solution on addition of water. Nitrogen is a homo-nuclear diatomic molecule which does not dissociate into aqueous solution.

Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

Electrolysis of which of the following compound will give $KOH$?

  1. Aqueous $KCl$ solution
  2. Fused $KCl$

  3. Fused potassium

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

Electrolysis of aqueous $KCl$ solution will give $KOH$. This is similar to the preparation of $NaOH$ by electrolysis of aqueous $NaCl$ solution. The electrolysis of fused $KOH$ will give potassium metal.

Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

During electrolysis of brine solution, product obtained at cathode and anode are:

  1. hydrogen and chlorine gas respectively

  2. chlorine and hydrogen gas respectively

  3. sulphate and chlorine gas respectively

  4. sodium and hydrogen gas respectively
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

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

Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

Oxygen and hydrogen gas are produced at the anode and cathode respectively, during the electrolysis of fairly concentrated aqueous solution of:

  1. $K _2SO _4$
  2. $AgNO _3$
  3. $H _2SO _4$
  4. $NaOH$
Reveal answer Fill a bubble to check yourself
A,C,D Correct answer
Explanation

As the reduction potential of $K^+$ and $ Na^+$ are lower than hydrogen ion, hydrogen ion gets preferably reduced and hydrogen gas is produced at the cathode.
Also, as oxidation potential of $OH^-$ is higher than sulphate ion, it will oxidise first and oxygen is evolved at the anode.

Hence, a fairly concentrated electrolytic aqueous solution of $K _2SO _4,\ H _2SO _4$ and $NaOH$ produces oxygen and hydrogen gas.

Multiple choice chemistry chemical changes electrochemical reactions electrolysis and its applications electrolytic cells and electrolysis

A dilute solution of sulphuric acid during electrolysis liberate O$ _2$ gas at the anode. 

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Because  ${ SO } _{ 4 }^{ 2- }$ mobility is very less as compared to ${ OH }^{ - }$ . So instead of ${ SO } _{ 4 }^{ 2- },{ OH }^{ - }$ undergo oxidation to form ${ O } _{ 2 }$ at anode. 

Also oxidation potential of ${ OH }^{ - }$ is more than ${ SO } _{ 4 }^{ 2- }$ 

Multiple choice chemistry nitrogen and sulfur nitrogen gas component of air - nitrogen nitrogen

Assertion (A): Anhydrous Calcium chloride is used as catalyst in cyanamide process
Reason (R): Catalyst increases the rate of reaction.

  1. Both (A) and (R) are true and (R) is the correct explanation of (A)

  2. Both (A) and (R) are true and (R) is not the correct explanation of (A)

  3. (A) is true and (R) is false

  4. (A) is false but (R) is true
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Catalyst increases the rate of reaction both in forward and reverse direction by decreasing the activation energy.
In cyanamide process, calcium chloride is used to increase the rate.

Multiple choice evs look, learn and experience matter: states, classification and properties study of matter general introduction: importance and scope of chemistry

What will be the product, if dilute hydrochloric acid is added to $FeS$?

  1. Element

  2. Mixture

  3. Compound

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

If you heat iron filings ans sulphur to a sufficiently high temperature you form iron sulphide 
$Fe + S \rightarrow FeS$
If you add HCl to this the following reaction occurs: 
$FeS + 2HCl \rightarrow FeCl _2 + H _2S$ 
$H _2S$ gas is given off and iron chloride is produced. 

Both are chemical compounds.

Multiple choice evs look, learn and experience matter: states, classification and properties study of matter general introduction: importance and scope of chemistry

What is formed if a mixture of powdered iron and sulphur is heated in a test tube?

  1. An element

  2. A mixture

  3. A compound

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

A mixture is made when you combine matter in a way where the components can be separated again. A compound results from a chemical reaction between components, forming a new substance. For example, you can combine iron filings with sulfur to form a mixture. All it takes is a magnet to separate the iron from the sulfur. On the other hand, if you heat the iron and sulfur, you form iron sulfide, which is a compound.
$Fe+S \rightarrow FeS$