Chemistry Questions

Q:

Which one of the following elements will be an isobar of calcium if the atomic number of calcium is 20 and its mass number is 40?

 

A) Element with 18 neutrons and 20 protons  B) Element with 19 neutrons and 18 protons 
C) Element with 19 neutrons and 20 protons  D) Element with 18 neutrons and 22 neutrons
 
Answer & Explanation Answer: D) Element with 18 neutrons and 22 neutrons

Explanation:
Isobar: one of two or more atoms having equal atomic weights but different atomic numbers.
 
                    Mass number     Electrons      Neutrons
    Calcium            40                    20                 20
 
     Argon              40                    18                 22
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0 2060
Q:

Which one of the following elements is used as a timekeeper in atomic clocks?

A) Potassium B) Caesium
C) Calcium D) Magnesium
 
Answer & Explanation Answer: B) Caesium

Explanation:

When exposed to certain frequencies of radiation, such as radio waves, the subatomic particles called electrons that orbit an atom's nucleus will "jump" back and forth between energy states. Clocks based on this jumping within atoms can therefore provide an extremely precise way to count seconds.It is no surprise then that the international standard for the length of one second is based on atoms. Since 1967, the official definition of a second is 9,192,631,770 cycles of the radiation that gets an atom of the element called caesium to vibrate between two energy states.

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0 2058
Q:

Magnesium (Mg) + Oxygen (O2) = ?

A) Mg2O B) MgO4
C) O2Mg D) MgO
 
Answer & Explanation Answer: D) MgO

Explanation:
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4 2057
Q:

What element is used to disinfect swimming pools?

A) Fluorine B) Chlorine
C) Bromine D) Sulphur
 
Answer & Explanation Answer: B) Chlorine

Explanation:
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5 2038
Q:

Vinegar is __________ .

A) diluted acetic acid B) glacial acetic acid
C) glacial formic acid D) diluted formic acid
 
Answer & Explanation Answer: A) diluted acetic acid

Explanation:
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1 2033
Q:

The compound used in prickly-­heat powder to prevent excessive sweating is

A) Boric acid B) Phosphoric acid
C) Carbonic acid D) Sulphonic acid
 
Answer & Explanation Answer: A) Boric acid

Explanation:
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Q:

Which among the following has the maximum density?

A) Water B) Ice
C) Ethylene D) Acetone
 
Answer & Explanation Answer: A) Water

Explanation:
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0 2033
Q:

The number of electron levels in a magnesium atom is

A) 3 B) 2
C) 1 D) 0
 
Answer & Explanation Answer: A) 3

Explanation:
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