Tag: chemistry

Quizzes (490) Questions (9892)

Questions Related to chemistry

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

Inflammable substances have?

  1. Low ignition temperature

  2. Highest ignition temperature

  3. Moderate ignition temperature

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

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

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

  1. Fuel

  2. Air

  3. Heat

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
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 $D$.


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

Which of the following is the most common fire extinguisher?

  1. Foam
  2. $CO _2$

  3. Water

  4. Dry powder
Reveal answer Fill a bubble to check yourself
C Correct answer
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 $C$.

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

Choose the correct statement from the following.


Forest fires are usually due to ______________.

  1. carelessness of humans

  2. heat of sun

  3. cutting of trees

  4. lightning strike
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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:

  1. metallurgy

  2. leaching

  3. gravity separation

  4. forth floatation process
Reveal answer Fill a bubble to check yourself
C Correct answer
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.
Multiple choice chemistry fluid pressure examples of hydraulic press applications of pascal's law pascal's law and its applications

Sand and sawdust can be separated by _________.

  1. gravity separation

  2. calcination

  3. magnetic separation

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  1. levigation

  2. leaching

  3. magnetic separation

  4. liquation
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  1. Magnetic

  2. Froth floatation

  3. Hydraulic

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

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

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

  1. specific gravities

  2. mass

  3. type of material

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  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. $4OH^- _{(aq)}+4e^-\rightarrow 2H _2O _{(l)}$
Reveal answer Fill a bubble to check yourself
A Correct answer
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: $2H _{2(g)}+O _{2(g)}\rightarrow 2H _2O _{(l)}$