Tag: chemistry

Questions Related to chemistry

Separation of two substances by crystallisation depends upon their differences in:

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  1. densities

  2. solublity

  3. melting point

  4. boiling point

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Correct Option: B
Explanation:

Separation of $2$ substances by crystallization depends upon their difference in solubility as more soluble impurity will go into the solution and less soluble component will crystallize out.

The most penetrating atom smashing particle is 

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  1. neutron

  2. proton

  3. alpha particle

  4. deuteron

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Correct Option: A
Explanation:

Neutron has highest penetrating power and low ionizing power. 

So, option A is correct answer.

Boiling water reactor and pressurized water reactors are  

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  1. nuclear reactor

  2. solar reactor

  3. OTEC

  4. Biogas reactor

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Correct Option: A

In a nuclear reactor, heavy water is used as a :

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  1. Controlling material

  2. Moderator

  3. Fuel

  4. Heat exchanger

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Correct Option: B
Explanation:

Heavy water ($D _{2}O$) is used as moderator. Most of the fast neutrons produced escape from the rod and enter into the moderator. These neutrons make collisions with particles of moderator and slow down.

The critical mass of fissionable $U^{235}$ can be reduced by

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  1. adding impurities

  2. heating material

  3. surrounding it by a neutron-reflecting material

  4. surrounding it by a neutron-absorbing material

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Correct Option: C
Explanation:

Surrounding a spherical critical mass with a neutron reflector reduces the mass needed for criticality.
A common material for a neutron reflector is beryllium metal.

Assertion (A) : Fragments produced in the fission of $U^{235}$ are radioactive
Reason (R) : The fragments have abnormally high proton to neutron ratio

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  1. Both A and R are true and R is correct explanation of A

  2. Both A and R are true and R is not correct explanation of A

  3. A is true but R is false

  4. A is false but R is true

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Correct Option: C
Explanation:

Fragments produced in the fission of $U^{235}$ are radioactive.
The fragments have the neutron of proton ratio about 1.6.
So, Assertion is correct but reason is false.

Consider the following statements A and B and identify the correct statements. 
Statement A : $p-n; p-p; n-n$ forces between nucleons are not equal and charge dependent
statement B : In nuclear reactor the fission reaction will be in accelerating state if the value of neutron reproduction factor is $k>1$

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  1. Both A and B are correct

  2. Both A and B are wrong

  3. A is wrong B is correct

  4. A is correct B is wrong

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Correct Option: C
Explanation:

Nuclear forces is charge independent
i.e. $F _{pp} = F _{pn} = F _{nn}$
If the K>1 the fission reaction will be in accelerating state.
So, correct choice is option C.

Which of the following are used as Control Rods :


a) Boron rods
b) Cadmium rods
c) Copper rods

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  1. a is correct

  2. b is correct

  3. c is correct

  4. a,b are correct

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Correct Option: D
Explanation:

Cadmium and Boron rods are used as control rods in a nuclear reactor as , they are capable of absorbing many neutrons without themselves fissioning.
So, correct choice is option D.

Thermal neutrons are 

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  1. Prompt neutrons

  2. Slow neutrons

  3. Neutrons which are in the nucleus

  4. Neutrons from the sun

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Correct Option: B
Explanation:

Slow moving neutrons are called thermal neutrons.
So, correct choice is option B.

In a critical chain reaction, energy is released at

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  1. increasing rate

  2. steady rate

  3. decreasing rate

  4. none

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Correct Option: B
Explanation:

In a critical chain reaction $K=1$,
where $K$ is the reproduction factor defined as the ratio of number of neutrons in any particular generation to the number of neutrons in the preceding generation.
As $K$ is $1$, energy is released in steady state.