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 combustion extinguishing fire ways to control fire combustion, fuels and flame

A white solid $X$ reacts with dil.$HCl$ to give colourless gas which is used in fire extinguishers. The solid $X$ is:

  1. $NaCl$
  2. $CH _2COONa$
  3. $Na _2CO _3$
  4. $NaHCO _3$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Sodium bicarbonate can be used for fire extinguishers purpose as it releases carbon dioxide. 


The following reaction takes place: 

$ NaHC{ O } _{ 3 }(X)\ +\ HCl\ \rightarrow \ NaCl\ +\ C{ O } _{ 2 }\ +\ { H } _{ 2 }O $

Hence, the correct option is $\text{D}$

Multiple choice chemistry combustion extinguishing fire ways to control fire combustion, fuels and flame

Fire extinguishers contain $H _{2}SO _{4}$ and:

  1. $NaHCO _{3}$ and $Na _{2}CO _{3}$
  2. $NaHCO _{3}$ solution
  3. $Na _{2}CO _{3}$
  4. $Ca _{2}CO _{3}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Soda-acid fire extinguishers work by reacting sulfuric acid with sodium bicarbonate (NaHCO3) to produce carbon dioxide gas, which displaces oxygen and puts out the fire. Option A is the standard chemical composition for this type of extinguisher.

Multiple choice chemistry combustion extinguishing fire ways to control fire combustion, fuels and flame

How will you distinguish between fire extinguishing action of water and $CO _2$? 

  1. Water helps to extinguish a fire in two ways: (1) It brings the temperature of the combustible material below its ignition temperature. (2) The water vapour formed due to the heat of fire cuts the supply of oxygen.

  2. Carbon dioxide is highly volatile. So, it immediately vaporises to cut off the supply of air. In the absence of supporter of combustion, fire is extinguished.
  3. Both $A$ and $B$

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

Both options A and B describe the difference between fire extinguishing action of water and $CO _2$.

  • Water helps to extinguish a fire in two ways: it cools the substance that undergoes combustion and brings the temperature of the combustible material below its ignition temperature. The water vapor formed due to the heat of fire surrounds the substance that undergoes combustion and cuts the supply of oxygen. 
  • Carbon dioxide is highly volatile and it is heavier than oxygen. So, it immediately vaporizes to cut off the supply of air. In the absence of supporter of combustion, fire is extinguished. Also, it does not damage electrical equipment.

Multiple choice chemistry energy fuel cell fuel cells electrochemistry, rechargeable batteries, and fuel cells

In a $H _2 - O _2$ fuel cell, combustion of hydrogen occurs to:

  1. remove adsorbed oxygen from electrode surface

  2. create potential difference between the two electrodes

  3. produce high purity water

  4. generate heat
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Combustion of hydrogen occur in ${ H } _{ 2 }-{ O } _{ 2 }$ fuel cell because of difference in potential between two electrode. So on one electrode oxidation occur while on another reduction.

Multiple choice chemistry the s-block elements (alkali and alkaline earth metals) common salt some useful compounds in everyday life salts and their properties

When picric acid is treated with aqueous sodium bicarbonate $ \left( \mathrm { NaH }  ^{ 14 } \mathrm { CO } _ { 3 } \right) $, a gas is liberated with effervescence. The gas evolved would be

  1. $ H _ { 2 } $
  2. $ \mathrm { CO } _ { 2 } $
  3. $ ^ { 14 } \mathrm { CO } _ { 2 } $
  4. $ \mathrm { NO } _ { 2 } $
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice chemistry substances in common use salts and their properties study of some important salts salts used in daily life

The metal whose hydroxide does not decompose on heating but its nitrate decomposes is:

  1. $Ca$
  2. $Al$
  3. $Na$
  4. $Fe$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$NaOH \xrightarrow {heat} $ no reaction
$NaNO _3 \xrightarrow {heat} NaNO _2+\frac{1}{2}O _2$

The metal whose hydroxide does not decompose on heating but its nitrate decomposes is sodium.

Multiple choice chemistry substances in common use salts and their properties study of some important salts salts used in daily life

Which one of the following products is formed when a mixture of steam, sulphur dioxide gas and oxygen gas (from air) is passed over dry lumps of common salt, the sodium chloride?

  1. $ Na _2SO _3 $
  2. $ Cl _3 $
  3. $ NaHSO _3 $
  4. $ Na _2SO _4 $
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Hargreaves process:
$ 4NaCl (s) + 2SO _2 (g) + 2H _2O (g) + O _2 (g) \longrightarrow 2Na _2SO _4 + 4HCl $

Multiple choice hydrogen ion scale or the ph scale inorganic analysis chemical analysis and investigation practical work chemistry
Unknown metal Appearance Reactions with dilute HCl Reaction with dilute HNO$ _3$
 (1) Dull gray solid with white oxide coating  Dissolved with bubbles of clear gas  Dissolved with bubbles of clear gas
 (2) Solid; lustrous smooth silver-gray surface No reaction  Dissolved with bubbles of orange gas

The addition of dilute HNO$ _3$ to unknown metal (2) produced an orange gas. Which of the following is the orange gas?

  1. Cl$ _2$
  2. H$ _2$
  3. O$ _2$
  4. CO$ _2$
  5. NO$ _2$
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

The addition of dilute $HNO _3$ to unknown metal (2) (silver metal) produced an orange gas nitrogen dioxide $\displaystyle (NO _2)$.
Note: Various gases have following colours.
$Cl _2-$ green
$H _2-$ colorless
$O _2-$ colorless
$CO _2-$ colorless
$NO _2-$ orange/brown

Multiple choice chemistry manmade materials synthetic rubber rubber polymer

A : A mixture of raw rubber and sulphur on heating at $373:K$ - $415:K$ gives vulcanised rubber.
R : ZnO decreases the rate of vulcanisation of rubber.

  1. both A and R are correct and R is the correct explanation of the A

  2. both A and R are correct but R is not the correct explanation of the A

  3. A is correct but R is incorrect

  4. A is incorrect but R is correct
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Natural rubber becomes soft at high temperature (>335 K) and brittle at low temperatures (<283 K) and shows high water absorption capacity. It is soluble in non-polar solvents and is non-resistant to attack by oxidising agents. 

To improve upon these physical properties, a process of vulcanisation is carried out. This process consists of heating a mixture of raw rubber with sulphur and an appropriate additive at a temperature range between 373 K to 415 K. On vulcanisation, sulphur forms cross links at the reactive sites of double bonds and thus the rubber gets stiffened.

In sulfur vulcanization of natural rubber, the types of cross-links formed largely depend on the vulcanization system. The vulcanizing agents are zinc oxide (ZnO), stearic acid, accelerators, and sulfur. Conventional ZnO, or micro ZnO, is one of the basic components of rubber compounds and acts as an activator for rubber crosslinking by sulfur or sulfur donors.

Hence, reason given is incorrect. So, option C is correct.
Multiple choice chemistry adsorption and colloids applications of colloids colloids around us the colloidal state

Which reagent, when mixed with ammonium sulfate and then heated, liberates ammonia?

  1. aqueous bromine

  2. dilute hydrochloric acid

  3. limewater

  4. potassium dichormate (VI) in acidic solution
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Test for the ammonium ion is adding a base then warming and then ammonia gas is produced therefore answer is C because limewater is $Ca(OH) _2$ which is a base and when it reacts with an ammonium ion which ammonium sulphate it produces ammonia gas overall reaction is:
$Ca(OH) _2 + (NH _4) _2SO _4 \rightarrow CaSO _4 + 2NH _3 + 2H _2O$
Multiple choice distinguish between black copper oxide and black manganese dioxide practical work chemistry

$CuO$ reacts with $HCl$ but $Cu$ does not, why?

  1. Copper has a higher reduction potential than hydrogen, it does not react with non-oxidising acids like $HCl$
  2. Copper has a lower reduction potential than hydrogen, it does not react with non-oxidising acids like $HCl$

  3. Copper is a least reactive metal hence does not react with any acid
  4. Both $Cu$ and $CuO$ does not react with $HCl$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Copper does not react with $HCl$ acid, but copper oxide does react. Copper has a higher reduction potential than hydrogen, hence it does not react with non-oxidising acids like $HCl$ or dil.$H _2SO _4$.
But metal oxides are basic substances, and so they generally react with acids forming respective salt and water.