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 geography in the land of kerala introduction to metallurgy occurrence of metals study of kerala

Which of the following oxides react to form slag in open hearth process?

  1. $CaO,CO$
  2. ${ P } _{ 2 }{ O } _{ 4 }, CaO$
  3. ${ P } _{ 2 }{ O } _{ 5 }, Si{ O } _{ 2 }$
  4. $CaO, { CO } _{ 2 }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
${CaCO _3} _{(s)}\longrightarrow CaO _{(s)}+{CO _2} _{(g)}$
$SiO _2+CaO \longrightarrow {CaSiO _3} _{(slag)}$
The calcium oxide formed by the decomposition reacts with various acidic impurities in the iron (mainly silica) to form slag which is essentially calcium silicate $(CaSiO _3)$ .
Multiple choice metallic and electrolytic conduction electrolysis chemical reactions electrochemistry chemistry

An alkali which dissociates partially on passage of an electric current is:

  1. sodium hydroxide

  2. nickel metal

  3. ammonium hydroxide

  4. copper
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

We have,

Sodium chloride is an ionic compound which is already present in the ionic form and completely dissociated on the passage of electric current,
Nickel and copper metal have higher reduction potential so, reduction takes place on passage of electric current,
ammonium hydroxide is a weak base it is partially dissociated on the passage of electric current. 

Multiple choice chemistry principles of metallurgy concentration of ore concentration of ores general principles of metallurgy

The purpose of stream of air in leaching process of $Ag _2S$ is to?

  1. Oxidises $Na _2S$ formed into $Na _2S _2O _3$
  2. Oxidises $Na _2S$ formed into $Na _2S _2O _4$
  3. Oxidises $Na _2S$ formed into $Na _2O$

  4. Act as catalyst
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In the leading of ${ Ag } _{ 2 }S$ (silver sulphide) with $NaCN$, a stream of air is passed because reversible nature of reaction between ${ Ag } _{ 2 }S$ and $NaCN$ and to oxidise ${ Na } _{ 2 }S$ formed into ${ Na } _{ 2 }{ SO } _{ 4 }$ and sulphur.

${ Na } _{ 2 }{ SO } _{ 4 }$ and sulphur $\Rightarrow { Na } _{ 2 }{ S } _{ 2 }{ O } _{ 4 }$

Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

A mixture of boron trichloride and hydrogen is subjected to silent electric discharge to form $'A'$ and $HCl. 'A'$ is miced with $NH _3$ and heated to $200^oC$ to form $'B'$. The formula of $'B'$ is

  1. $H _3BO _3$
  2. $B _2O _3$
  3. $B _2H _6$
  4. $B _3N _3H _6$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$2BCl _3+3H _2\underset {discharge}{\xrightarrow {electric}}\underset {(A)}{B _2H _6}+6HCl$.


$A$  is $B _2H _6$

$3B _2H _6+6NH _3\rightarrow 2B _3H _6N _3 + 12H _2$

So $B$  is $B _3N _3H _6$.

Hence option D is correct

Multiple choice chemistry the p-block elements - group 13 study of diborane some important compounds of boron study of boron

A compound $A$ of boron reacts with $NMe _3$ to give an adduct $B$ which on hydrolysis gives a compound $C$ and a gas $D$. Compound $C$ is an acid.


Gas $D$ is :

  1. hydrogen

  2. oxygen

  3. water

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Since compound $'A'$  of Boron reacts with ${ NMe } _{ 3 }$  to form an adduct $'B'$.  Thus compound $'A'$ is lewis acid.  Hydrolysis of $'B'$ gives  an acid $'C'$ and hydrogen gas.

 Diborane  $(A)$ ${ B } _{ 2 }{ H } _{ 6 }+{ 2NMe } _{ 3 }\longrightarrow { 2BH } _{ 3 }\cdot { NMe } _{ 3 }$  Adduct  $(B)$

${ BH } _{ 3 }\cdot { NMe } _{ 3 }+3{ H } _{ 2 }O\longrightarrow { H } _{ 3 }{ BO } _{ 3 }+{ NMe } _{ 3 }+6{ H } _{ 2 }$  Boric Acid $(C)$
Multiple choice chemistry air and water pollution control environmental impact: global warming green house effect geobiochemical cycle

On warming formic acid with ammoniacal silver nitrate, the product formed is 

  1. silver oxide

  2. metallic silver

  3. formaldehyde

  4. silver formate
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Formic acid acts as a reducing agent. When heated with ammoniacal silver nitrate (Tollens' reagent), it reduces silver ions to metallic silver, forming a silver mirror.

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

Concentrated nitric acid on reacting with any metal like copper releases gas with an irritating odour :

  1. $H _2 S$
  2. $CuS$
  3. $H _2$
  4. $NO _2$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Nitrogen dioxide is the chemical compound with the formula $NO _2$. It is one of several nitrogen oxides. $NO _2$ is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent air pollutant. Reduction of concentrated nitric acid by metal (such as copper).
$4 HNO _3 +Cu \rightarrow Cu(NO _3) _2+ 2 NO _2 + 2 H _2O$

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

Select the correct statement. 

  1. Mixture of $NH _4Cl$ and $NaNO _2$ on heating gives $N _2$ gas
  2. $CFC$ is used as refrigerating fluid and as propellant in aerosols
  3. Phosgene is formed when $P _4$ reacts with $NaOH$
  4. Phosgene dissolves in water forming $P _2O _5$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Heating a mixture of ammonium chloride (NH4Cl) and sodium nitrite (NaNO2) is a standard laboratory method for preparing pure nitrogen gas.

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

$(NH _4) _2Cr _2O _7$ on heating liberates gas. The same gas will be obtained by :

  1. heating $NH _4NO _2$
  2. heating $NH _4NO _3$
  3. treating $Mg _3N _2$ with $H _2O$
  4. heating $H _2O _2$ on $NaN0 _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
On heating, $(NH _{4}) _{2}Cr _{2}O _{7}$ gives, nitrogen gas. 

$(NH _{4}) _{2}Cr _{2}O _{7}\rightarrow N _{2}+Cr _{2}O _{3}+4H _{2}O$
          (Orange)                                 (Green)

But whenever, $NH _4NO _2$ and $NH _4NO _3$ heated, then nitrogen and nitrogen dioxide gas liberated.

$NH _{4}NO _{2}\rightarrow N _{2}+2H _{2}O$

$NH _{4}NO _{3}\rightarrow N _{2}O+2H _{2}O$

So, the correct option is $A$
Multiple choice chemistry preparation of gases nitrogen gas component of air - nitrogen nitrogen

Which of the following on heating will not evolve N$ _2$ gas?

  1. NH$ _{3}$ + NaNO$ _{2}$
  2. NH$ _{4}$Cl + NaNO$ _{2}$
  3. N$ _{2}$O + Cu
  4. (NH$ _{4}$)$ _{2}$Cr$ _{2}$O$ _{7}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The given reactions take place as:


$NH _3 + NaNO _2 \rightarrow NH _3NO _2 + Na$


$NH _4Cl + NaNO _2 \rightarrow N _2 + NaCl + 2H _2O$

$N _2O +Cu \rightarrow N _2 + CuO$

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



Hence, the reaction between ammonia and sodium nitrate do not evolve $N _2$ gas. 

Thus option A is the correct answer.

Multiple choice chemistry world energy needs coal petroleum non-renewable sources of energy

Ammonia liquor is prepared by dissolving:

  1. ammonia gas in alcohol

  2. ammonia gas in water

  3. ammonia gas in hydrochloric acid

  4. ammonia gas in caustic soda solution
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Ammonia liquor is prepared by dissolving Ammonia in water. Ammonia liquor is also known as ammonia water or some times known as ammonium hydroxide.
In aqueous solution, ammonia deprotonates a small fraction of the water to give ammonium and hydroxide according to the following equilibrium:
$ NH _3 +H _2O\rightarrow NH _4^{+} + OH^{-}$