Chemistry Questions

Q:

What is the gram formula mass of K2CO3?

A) 147 B) 138
C) 129 D) 116
 
Answer & Explanation Answer: B) 138

Explanation:

The gram formula mass of a compound is nothing but the molar mass.

The molar mass of K2CO3 (Potassium Carbonate) is given by

Atomic weights of individual elements are

 

K (Potassium) = 39 g

C (Carbon) = 12 g

O (Oxygen) = 16 g

 

Hence, that of K2CO3 = 39(2) + 12 + 16(3)

= 78 + 12 + 48

= 138.

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Q:

Which of the following elements has the highest electronegativity?

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

Explanation:

Electronegativity refers to the ability of an atom to attract shared electrons in a covalent bond. The higher the value of the electronegativity, the more strongly that element attracts the shared electrons.

Electronegativity increases from bottom to top in groups, and increases from left to right across periods. Thus, fluorine is the most electronegative element and lithium is the least.

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Q:

In atomic reactors,graphite is used as

A) lubricant B) fuel
C) linear of the ractor D) moderator
 
Answer & Explanation Answer: D) moderator

Explanation:
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Q:

How many valence electrons are in carbon?

A) 2 B) 4
C) 6 D) 3
 
Answer & Explanation Answer: B) 4

Explanation:

The main group number for an element can be found from its column on the periodic table. For example, carbon is in group 4 and has 4 valence electrons. Oxygen is in group 6 and has 6 valence electrons.

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Q:

Washing soda is the common name for

A) Sodium Bicarbonate B) Calcium Carbonate
C) Sodium Carbonate D) Calcium Bicarbonate
 
Answer & Explanation Answer: C) Sodium Carbonate

Explanation:

Washing soda is the common name for Sodium Carbonate (Na2CO3). It is also called as Soda Ash.

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Q:

Dust particles in the air of large industrial cities are removed by 

A) Sedimentation B) Electrophoresis
C) Tyndall effect D) Brownian movement
 
Answer & Explanation Answer: B) Electrophoresis

Explanation:

Dust particles such as coal dust(smoke) are fine particle of a solid (carbon in the case of smoke) dispersed in air. They are colloidal systems and the particles are charged either positive or negative. In an applied electrical field, they are attracted towards the opposite electrodes. Movement of the particles towards the electrodes is known as 'electrophoresis'. Hence electrophoresis is applied to remove smoke within the chimeny itself without allowing it to escape into the air and cause nuisance.

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Q:

Which of the following metal is generally used for making filaments of bulb?

A) W B) Ag
C) Fe D) Rh
 
Answer & Explanation Answer: A) W

Explanation:

W is the symbol for chemical element Tungsten or Wolfram.

It is used in making filaments of bulbs.

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Q:

Iron rusting, chemical or physical change

A) Chemical B) Physical
C) Both A & B D) None of the above
 
Answer & Explanation Answer: A) Chemical

Explanation:

In rusting the Iron ore make a chemical reaction with the oxygen in the presence of water and environmental or atmospheric moisture to produce an Iron oxide. Iron oxide is otherwise called as rust.


The rusting of iron is a chemical change because it is two substances reacting together to make a new substance.

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