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 Chemistry Questions

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Q:

which of the following are chemical changes?

A) Cooking of Food

B) Digestion of Food

C) Freezing of water

D) Water is heated up

A) A & B B) A, B & C
C) C & D D) All the above
 
Answer & Explanation Answer: A) A & B

Explanation:

A) Cooking of Food  ------ Chemical Change

B) Digestion of Food ----- Chemical Change

C) Freezing of water ----- Physical Change

D) Water is heated up ---- Physical Change

because here the chemical composition of the substance changes in A & B only.

 

Since we know that, If the chemical composition is changing then it is a chemical change and if the chemical composition is remaining the same, then it is a physical change.

 

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Q:

A ‘breath test’ used by traffic police to check drunken driving uses ____?

A) Turmeric on filter paper B) Silica gel coated with silver nitrate
C) potassium permanganate-sulphuric acid D) Potassium dichromatic-sulphuric acid
 
Answer & Explanation Answer: D) Potassium dichromatic-sulphuric acid

Explanation:
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Q:

Brass gets discoloured in air because of the presence of which of the following gases in air  ?

A) Hydrogen sulphide B) Oxygen
C) Nitrogen D) Carbon dioxide
 
Answer & Explanation Answer: A) Hydrogen sulphide

Explanation:
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Q:

What is the structure of IF7 ?

A) Triagonal bipyramid B) Pentagonal bipyramid
C) Square pyramid D) tetrahedral
 
Answer & Explanation Answer: B) Pentagonal bipyramid

Explanation:

In IF7 out of 7 Flourine atoms 5 of them are placed on a plane in Pentagon shape .In remaining 2 flourines one is placed above the plane and other below the plane each at 90 degrees

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Q:

Which of the following reactions are exothermic?

 

1)   C + O2  → CO22)  2Mg + O2  → 2MgO3)  CuSO4 + 5H2O  → CuSO4.5H2O4)  All the above

A) 1 B) 2
C) 3 D) 4
 
Answer & Explanation Answer: D) 4

Explanation:

Here all the given options are Exothermic reactions. Exothermic reactions are those reactions which involves the release of heat.

 

Generally all the combining reactions are exothermic in nature.

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Q:

Place these hydrocarbons in order of decreasing boiling point.

1. Paraffin

2. Octadecane

3. Hexane

4. Neohexane and

5. Ethane

A) Paraffin > Octadecane > Neohexane > Hexane > Ethane B) Paraffin > Octadecane > Hexane > Neohexane > Ethane
C) Hexane > Paraffin > Octadecane > Neohexane > Ethane D) None of the above
 
Answer & Explanation Answer: B) Paraffin > Octadecane > Hexane > Neohexane > Ethane

Explanation:

In hydrocarbon, the boiling point directly varies with the length of carbon chain. On increasing the number of carbon atom, the boiling point of the compound also increases. Paraffin contains highest number of carbon atoms whereas, ethane is comprised of two carbon atoms.

 

The decreasing order of boiling point of mention compounds is written as follows:

Paraffin > Octadecane > Hexane > Neohexane > Ethane

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Q:

What is the IUPAC name for the following compound?

 

H3C-C≡C-H

A) Acetylene B) Methyl acetylene
C) Butanol D) Decanoic Acid
 
Answer & Explanation Answer: B) Methyl acetylene

Explanation:

The IUPAC name of the compound is Methyl Acetylene or Propyne.

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Q:

When formaldehyde and potassium hydroxide are heated , we get 

A) Acetylene B) Methyl alcohol
C) Methane D) Ethyl formate
 
Answer & Explanation Answer: B) Methyl alcohol

Explanation:
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