Chemistry

Chemical Reactions and Processes

626 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 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 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^{-}$

Multiple choice chemistry metals physical properties of metals and non-metals some physical properties of metals general characteristics and uses of metals

Four metals $P$, $Q$, $R$ and $S$ react with water as given below:
I. $P$ reacts with cold water
II. $Q$ reacts with hot water
III. $R$ reacts with steam
IV. Red hot $S$ reacts with steam.
Then, highly reactive metal is:

  1. $P$
  2. $Q$
  3. $R$
  4. $S$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The highly reactive metal is $P$ as it reacts with cold water. This is because, the reaction with cold water requires lowest energy of activation.

Multiple choice commercial applications global environmental change causes of resource depletion causes of greenhouse effect ozone layer depletion

HCs are thermodynamically not stable towards

  1. Acidification

  2. Decomposition

  3. Reduction

  4. Oxidation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Hydrocarbons (HCs) are generally susceptible to oxidation reactions, especially in the presence of oxygen or oxidizing agents, which is why they are not thermodynamically stable in such environments.

Multiple choice chemistry chemistry of non-metals physical properties of non-metals uses of metals and non metals physical properties of metals and non-metals

Platinum metal can be dissolved in:

  1. hot conc. HCl
  2. hot conc. $HNO _3$
  3. hot dil. $H _2SO _4$
  4. a mixture of conc. HCl and $HNO _3$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • Traditional aqua regia is a mixture of concentrated nitric and hydrochloric acids in a ratio of 1:3 that can dissolve noble metals such as gold, platinum and palladium, even though the metals are not soluble in either acid alone.
  • Hence option D is correct answer.
Multiple choice chemistry nitrogen and sulfur ammonia-properties and uses ammonia compounds of nitrogen - ammonia

Statement 1: When HCl gas and $NH _3$ gas come into contact, a white smoke forms.
Statement 2: $NH _3$ and HCl react to form a white solid, ammonium chlorate.

  1. <p>Both Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1.</p>

  2. <p>Both Statement 1 and Statement 2 are correct and Statement 2 is not the correct explanation of Statement 1.</p>

  3. <p>Statement 1 is correct but Statement 2 is not correct.</p>

  4. <p>Statement 1 is not correct but Statement 2 is correct.</p>

  5. <p>Both the Statement 1 and Statement 2 are not correct.</p>
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When ammonia and $HCl$ come in contact, they form ammonium chloride.
$\displaystyle  NH _3+HCl \rightarrow NH _4Cl$