Chemistry Questions

Q:

Which is a pair of allotropes?

A) carbon-16 and carbon-12 B) diamond and graphite
C) carbon dioxide and graphite D) diamond and carbon dioxide
 
Answer & Explanation Answer: B) diamond and graphite

Explanation:

Allotropes are the different physical forms of an element. Here in the given options, diamond and graphite are the pair of allotropes of carbon.

 

Some more examples are Molecular oxygen and ozone are pair of allotropes, Black and red phosphorous are also pairs of allotropes.

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Q:

Chloroform used as anaesthetic should be preserved in the dark in tightly stoppered bottles because otherwise

A) it becomes coloured B) it gets evaporated in air
C) it gets oxidised to phosgene D) it gets decomposed to chloropicrin
 
Answer & Explanation Answer: C) it gets oxidised to phosgene

Explanation:

Chloroform, CHCl3 is easily oxidised to the highly poisonous gas known as phosgene or carbonyl chloride COCl2. Hence if it is used as anaesthetic it should be kept free from sunlight and air.

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Q:

Which of the following gases is present under pressure in soft drinks?

A) Nitrous oxide B) Oxygen
C) Nitrogen D) Carbon dioxide
 
Answer & Explanation Answer: D) Carbon dioxide

Explanation:

Carbon dioxide is present under pressure in soft drinks.

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Q:

Which one of the following laws directly expalins the law of coservation of mass

A) Hund's rule B) Dalton's law
C) Avogadro's law D) Berzelius hypothesis
 
Answer & Explanation Answer: C) Avogadro's law

Explanation:
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Q:

Of the following radiations, the most easily stopped by air

A) alpha - rays B) beta - rays
C) gamma -rays D) x - rays
 
Answer & Explanation Answer: A) alpha - rays

Explanation:
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Q:

The structure of IF7 is

A) Pentagonal bipyramid B) Square pyramid
C) Trigonal bipyramid D) Octahedral
 
Answer & Explanation Answer: A) Pentagonal bipyramid

Explanation:

Hybridisation of iodine is sp3d3

 

So, the structure is pentagonal bipyramid.

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Q:

Gases used in normal welding?

A) Oxygen and Acetylene B) Acetylene and Nitrogen
C) Oxygen, Hydrogen and Acetylene D) Oxygen and Hydrogen
 
Answer & Explanation Answer: A) Oxygen and Acetylene

Explanation:

Normal Gas welding use oxygen-acetylene.

 

Depending on what materials you are welding, there are some more options that might be used.

For example - MIG/TIG use Argon, MAG use an argon-something mix.

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Q:

Reactions that require CO2 take place in

A) the Calvin cycle alone B) the light reactions alone
C) Both A & B D) the chloroplast, but is not part of photosynthesis
 
Answer & Explanation Answer: A) the Calvin cycle alone

Explanation:
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