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 chemical kinetics introduction to chemical kinetics understanding chemical kinetics rate of chemical reaction

A chemist puts a sample of dilute aqueous hydrochloric acid into beaker $1$. She adds a sample of zinc and measures the rate of production of hydrogen gas.
She then puts a different sample of dilute aqueous hydrochloric acid into beaker $2$. She adds a different sample of zinc and measure the rate of production of hydrogen gas.
The rate of the reaction in beaker $2$ is greater than the rate of the reaction in beaker $1$.
Which factors could help to explain this observation?
$1$. The reaction in beaker $1$ has a higher activation energy than the reaction in beaker $2$.
$2$. The zinc in beaker $1$ is in larger pieces than the zinc in beaker $2$.
$3$. The acid in beaker $1$ is at a lower concentration than the acid in beaker $2$.

  1. $1, 2$ and $3$ are correct
  2. $1$ and $2$ only are correct
  3. $2$ and $3$ only are correct
  4. $1$ only is correct
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Since the rate of reaction in beaker $2$ is greater than the rate of reaction in beaker $1$, thus the concentration of acid in beaker $2$ will be greater than that in beaker $1$.
Also, lower the activation energy, the faster the rate of reaction. Thus the reaction in beaker $2$ has a lower activation energy than the reaction in beaker $2$.
Also the zinc in beaker $2$ will be in small pieces than that in beaker $2$ as large pieces will break slowly to react.
Hence $1, \; 2$ and $3$ are correct.
Multiple choice chemistry carbon compounds some important carbon compounds ethanol and ethanoic acid introduction to alcohols - ethanol

 When ethanol react with sodium,which gas will produce?

  1. hydrogen

  2. oxygen

  3. sodium ethoxide

  4. carbon dioxide
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If a small piece of sodium is dropped into some ethanol, it reacts steadily to give off bubbles of hydrogen gas and leaves a colourless solution of sodium ethoxide, $CH _3CH _2ONa$ and hydrogen gas is evolved.

$2C _2H _5OH + 2Na \rightarrow 2C _2H _5ONa + H _2$ Option A is correct.

Multiple choice chemistry hydrocarbons introduction to alkenes - ethyne acetylene alkynes

The compound used in Hawker's lamp and in light houses for illumination purposes is :

  1. methane

  2. ethane

  3. ethylene

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

Acetylene is used in-
Illumination of cycle lamps, hawker's lamps and buoys in light houses.
Producing oxyacetylene flame for welding and cutting.

Multiple choice chemistry hydrocarbons introduction to alkenes - ethyne acetylene alkynes

Product formed on electrolysis of potassium salt of fumaric and maleic acid is

  1. Ethene

  2. Ethane

  3. Butane

  4. Ethyne

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

Electrolysis of the potassium salts of fumaric or maleic acid (unsaturated dicarboxylic acids) yields ethyne via Kolbe's electrolysis.

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 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