Tag: chemistry

Questions Related to chemistry

Inflammable substances have?

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

  1. Low ignition temperature

  2. Highest ignition temperature

  3. Moderate ignition temperature

  4. None of the above

Show answer
Correct Option: A
Explanation:

The substances which has a very low ignition temperature and can catch fire easily with a flame are called as inflammable substances. It is the ability of a substance to burn or ignite, causing fire or combustion. For eg; LPG, petrol etc. 

Fire can be controlled by removing which of the following factor?

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

  1. Fuel

  2. Air

  3. Heat

  4. All of the above

Show answer
Correct Option: D
Explanation:

The three essential things required to control fire are fuel, heat and air. 

The air supplies oxygen and heat raises the temperature of the fuel beyond the ignition temperature. 
Fire can be controlled by removing any one of these factors. 


Hence, the correct option is $D$.


Which of the following is the most common fire extinguisher?

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

  1. Foam

  2. $CO _2$

  3. Water

  4. Dry powder

Show answer
Correct Option: C
Explanation:

The cheapest and most widely used fire extinguisher is water because it is easily available. But it is preferably used for class A fires. like fire in solids, wood, paper etc. Not suitable for Class B (Liquid) fires, or where electricity is involved. 


Hence, the correct answer is option $C$.

Choose the correct statement from the following.


Forest fires are usually due to ______________.

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

  1. carelessness of humans

  2. heat of sun

  3. cutting of trees

  4. lightning strike

Show answer
Correct Option: A
Explanation:

Forest fires are usually due to campfires, burning of debris, littering of cigarettes or intentional acts of arson.


Hence, it is generally a result of careless activities of humans.

Hence the correct option is A.

The powdered ore is agitated with water or washed with running stream of water. The heavy ore particles and lighter impurities are separated. This method of concentration is known as:

chemistry fluid pressure examples of hydraulic press applications of pascal's law pascal's law and its applications

  1. metallurgy

  2. leaching

  3. gravity separation

  4. forth floatation process

Show answer
Correct Option: C
Explanation:
  • Hydraulic washing is based on the difference between specific gravities of the ore and the gangue particles. 
  • It is, therefore, a type of gravity separation. In one such process, an upward stream of running water is used to wash the powdered ore. 
  • The lighter gangue particles are washed away and the heavier ore particles are left behind.

Sand and sawdust can be separated by _________.

chemistry fluid pressure examples of hydraulic press applications of pascal's law pascal's law and its applications

  1. gravity separation

  2. calcination

  3. magnetic separation

  4. none of these

Show answer
Correct Option: A
Explanation:

Sand and saw dust can be separated by gravity separation method. The process can be used for separating insoluble substances which are heavier than liquid by allowing them to settle down on their own due to gravity.

The method of concentration of the ore that makes use of difference in density between ore and impurities is called __________.

chemistry fluid pressure examples of hydraulic press applications of pascal's law pascal's law and its applications

  1. levigation

  2. leaching

  3. magnetic separation

  4. liquation

Show answer
Correct Option: A
Explanation:

Levigation is based on the difference in densities of the metallic ore and gangue particles. Powdered ore is treated with a stream of running water when the lighter gangue particles are washed away and heavier ore particles are left behind.

Write the correct alternatives :
In the Wilfley table method, the particles of gangue are separated by...................separation method.

chemistry fluid pressure examples of hydraulic press applications of pascal's law pascal's law and its applications

  1. Magnetic

  2. Froth floatation

  3. Hydraulic

  4. Gravitational

Show answer
Correct Option: C
Explanation:

Hydraulic Washing :

In this method by flowing the powdered ore in a current of water, lighter rocky impurities can be washed away, for this, either wilfley table or Hydraulic classifier is used.

$\therefore$ option $"C"$ is correct.

Hydraulic washing is based on the differences in ___________ of the ore and gangue particles.

chemistry fluid pressure examples of hydraulic press applications of pascal's law pascal's law and its applications

  1. specific gravities

  2. mass

  3. type of material

  4. none of these

Show answer
Correct Option: A
Explanation:

Hydraulic washing is a type of gravity separation, which is based on gravity differences between the ore and the gangue particles. In this process, the lighter gangue particles are washed away by a stream of water, leaving behind the heavier ore.

The overall reaction of a hydrogen-oxygen fuel cell is:

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

  1. $2H _{2(g)}+O _{2(g)}\rightarrow 2H _2O _{(l)}$

  2. $2H _{2(g)}+4OH^- _{(aq)}\rightarrow 4H _2O _{(l)}+4e^-$

  3. $O _{2(g)}+2H _2O _{(l)}+4e^-\rightarrow 4OH^- _{(aq)}$

  4. $4OH^- _{(aq)}+4e^-\rightarrow 2H _2O _{(l)}$

Show answer
Correct Option: A
Explanation:
A fuel cell is an electrochemical cell that converts the chemical energy from a fuel into electricity through an electrochemical reaction of hydrogen fuelwith oxygen or anotheroxidizing agent.
The reactions which takes place in hydrogen-oxygen fuel cell are,
At cathode:$2H _{2(g)}+4OH^{-} _{(aq)}\rightarrow 4H _2O _{(l)}+4e^{-}$
At cathode:$O _{2(g)}+2H _2O _{(l)}+4e^{-}\rightarrow 4OH^{-} _{(aq)}$
Overall reaction: $2H _{2(g)}+O _{2(g)}\rightarrow 2H _2O _{(l)}$