The reaction CaO + H₂O → Ca(OH)₂ is a: MCQ with Answer and Explanation

The reaction CaO + H₂O → Ca(OH)₂ is a:
A. Displacement
B. Decomposition
C. Combination
D. Redox
Answer: Option C
Solution (By JKSSB Mock Tests)
Two reactants combine to form a single product, so combination (also called synthesis). No oxidation state change, so not redox. Decomposition is opposite.

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Practice More chemistry Questions

Question #1
Assertion (A): Methanol is highly toxic and can cause blindness if ingested. Reason (R): Methanol is metabolized in the body to formaldehyde and formic acid.
A. Both A and R are true and R is the correct explanation of A.
B. A is false but R is true.
C. A is true but R is false.
D. Both A and R are true but R is NOT the correct explanation of A.

Correct Answer: Option A


Explanation:
Methanol (wood alcohol) is highly toxic. When ingested, it is metabolized by the enzyme alcohol dehydrogenase into formaldehyde and then formic acid. Formic acid interferes with mitochondrial function, leading to metabolic acidosis, optic nerve damage, and blindness. Both statements are correct and R explains A.

This question belongs to: Science chemistry
Question #2
Which of the following is a homogeneous mixture?
A. Sand in water
B. Salt in water
C. Iron filings and sulfur
D. Oil and water

Correct Answer: Option B


Explanation:
A homogeneous mixture has uniform composition throughout. Salt completely dissolves in water, forming a single phase (solution). Oil and water are immiscible (heterogeneous). Sand in water is suspension (heterogeneous). Iron filings and sulfur can be heterogeneous unless alloyed.

This question belongs to: Science chemistry
Question #3
The modern periodic table is based on:
A. Atomic mass
B. Atomic number
C. Mass number
D. Number of neutrons

Correct Answer: Option B


Explanation:
The modern periodic law states that properties of elements are periodic functions of their atomic numbers (number of protons). This was established by Henry Moseley. Mendeleev's original table used atomic mass, but the modern table resolves anomalies by ordering by atomic number.

This question belongs to: Science chemistry