Chemistry Questions

Q:

A gas absorbs a photon of 355 nm and emits at two wavelengths. If one of the emissions is at 680 nm, the other is at :

A) 518 nm B) 1035 nm
C) 325 nm D) 743 nm
 
Answer & Explanation Answer: D) 743 nm

Explanation:

1λ=1λ1+1λ2

1355=1680+1λ2

1λ2=680-355680×355

λ2=743nm.

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Q:

An element which is preserved under water is 

A) sodium B) sulphur
C) red phosphorus D) white phosphorus
 
Answer & Explanation Answer: D) white phosphorus

Explanation:

White phosphorus undergoes spontaneous combustion when exposed to air. In order to prevent this spontaneous ignition, it is preserved under water. 

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27 9496
Q:

The fundamental particles present in equal numbers in neutral atoms are

A) protons and electrons B) neutrons and electrons
C) protons and neutrons D) protons and positrons
 
Answer & Explanation Answer: A) protons and electrons

Explanation:
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Q:

Which of these molecules are polar? Check all that apply.

A) SO2 B) CH2Cl2
C) PCl3 D) All the above
 
Answer & Explanation Answer: D) All the above

Explanation:

   1) SO2                  2) CH2Cl2                3) PCl3

polar1525846214.jpg image

How to check the given molecules are polar or non polar :

If the electronegativity of the two bonded atoms are different then the bond is polar. Although, some molecules contain polar bonds, the molecule may be non-polar. If the polarity of all the bonds present in the molecule are cancel each other then molecule is non-polar.

 

In the given options,

SO2  is polar because the dipole moments on the O do not cancel.

PCl3  is polar because the P-Cl bonds do not cancel out.

CH2Cl2  polar because the C-Cl bonds do not cancel.

 

Hence, in brief, Polar molecules are molecules with net dipole due to the presence of partial positive and partial negative charge.

For example, water is a polar molecule that has partial positive and partial negative charge on it. CO2 is a non polar compound.

 

Therefore, all the given options SO2, CH2Cl2 and PCl3 are Polar molecules.

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5 9475
Q:

Which one of the following is a natural colloid ?

A) Cane sugar solution B) Blood
C) Sodium chloride solution D) Urea solution
 
Answer & Explanation Answer: B) Blood

Explanation:
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26 9451
Q:

Which of the following is not a compound?

A) Brass B) Quick lime
C) Marble D) Soda ash
 
Answer & Explanation Answer: A) Brass

Explanation:

Among the given options Brass is not a compound. Since it is an alloy, it is a mixture. It is a mixture of copper and zinc.

Which_of_the_following_is_not_a_compound1558074260.jpg image

 

 

 

The smallest part of a compound is called a molecule. It has a unique composition that is always the same.

 

Compound is a substance that consists of two or more elements. 

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12 9450
Q:

The outer electron configuration of Gd (Atomic No : 64) is

1. 4f75d16s2

2. 4f35d56s2

3. 4f85d06s2

4. 4f45d46s2

Answer

Answer : 1


 


Sol :


1. 4f75d16s2

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19 9383
Q:

Orlon is a polymer of

A) Dacron B) Acrylonitrile
C) Polyamide Nylon D) None of the above
 
Answer & Explanation Answer: B) Acrylonitrile

Explanation:

The monomeric unit of orlon polymer is Acrylonitrile. Orlon is also known as Polyacrylonitrile (PAN). 

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