The number of atoms in a molecule of phosphorus (P₄) is: MCQ with Answer and Explanation

The number of atoms in a molecule of phosphorus (P₄) is:
A. 8
B. 4
C. 2
D. 1
Answer: Option B
Solution (By JKSSB Mock Tests)
White phosphorus exists as P₄ tetrahedral molecules, containing 4 phosphorus atoms. So atomicity is 4. Sulfur is S₈, oxygen is O₂, ozone O₃. Atomicity is the number of atoms in a molecule of an element. Phosphorus is a non-metal. Red phosphorus is polymeric but P₄ is the common molecular form.

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Practice More chemistry Questions

Question #1
Which of the following is a characteristic property of ionic compounds?
A. They are good conductors of electricity in the solid state.
B. They have low melting and boiling points.
C. They are soluble in water and conduct electricity in molten or aqueous state.
D. They are soluble in non-polar solvents like benzene.

Correct Answer: Option C


Explanation:
Ionic compounds are soluble in polar solvents like water. In the solid state, ions are fixed in a lattice and cannot move, so they don't conduct. However, in molten or aqueous states, the ions become free to move, allowing them to conduct electricity. They generally have high melting points.

This question belongs to: Science chemistry
Question #2
The half-life of a substance is 4 years. In how many years will 1/16 of the original amount remain?
A. 16 years
B. 12 years
C. 8 years
D. 20 years

Correct Answer: Option A


Explanation:
Fraction remaining = (1/2)^n = 1/16 => n = 4 half-lives. Time = n × half-life = 4 × 4 = 16 years. After 1 half-life: 1/2, 2: 1/4, 3: 1/8, 4: 1/16. Radioactive decay is exponential. So after 16 years, only 1/16th of original radioactive atoms remain.

This question belongs to: Science chemistry
Question #3
Which allotrope of carbon is used in pencils?
A. Charcoal
B. Graphite
C. Fullerene
D. Diamond

Correct Answer: Option B


Explanation:
Pencil 'lead' is a mixture of graphite and clay. Graphite's layered structure allows it to leave marks on paper. Diamond is too hard and would tear paper. Fullerene is a nanomaterial, not for writing. Charcoal is used for drawing but not pencils.

This question belongs to: Science chemistry