Which of the following reactions is a double displacement reaction? MCQ with Answer and Explanation

Which of the following reactions is a double displacement reaction?
A. CaCO₃ → CaO + CO₂
B. BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl
C. 2Mg + O₂ → 2MgO
D. Zn + H₂SO₄ → ZnSO₄ + H₂
Answer: Option B
Solution (By JKExamLibrary)
In a double displacement reaction, ions of two compounds exchange places to form two new compounds. Here, Ba²⁺ and Na⁺ exchange their anions (Cl⁻ and SO₄²⁻) to form BaSO₄ (a white precipitate) and NaCl. This is also a precipitation reaction due to the formation of insoluble barium sulfate.

Discuss this Question (0)

No comments yet. Be the first to start the discussion!

Practice More chemistry Questions

Question #1
Which acid is known as 'Oil of Vitriol'?
A. Sulphuric acid
B. Acetic acid
C. Nitric acid
D. Hydrochloric acid

Correct Answer: Option A


Explanation:
Sulphuric acid (H₂SO₄) is historically called oil of vitriol because it was prepared by distilling green vitriol (ferrous sulfate heptahydrate). It is a dense, oily liquid. Nitric acid is aqua fortis, hydrochloric acid was called muriatic acid or spirit of salt. Sulphuric acid is the king of chemicals due to its widespread use in industries like fertilizer, petroleum refining, and chemical synthesis.

This question belongs to: Science chemistry
Question #2
Assertion (A): A catalyst does not change the equilibrium yield of a reaction. Reason (R): A catalyst speeds up both the forward and backward reactions equally.
A. A is false but R is true.
B. A is true but R is false.
C. Both A and R are true but R is NOT the correct explanation of A.
D. Both A and R are true and R is the correct explanation of A.

Correct Answer: Option D


Explanation:
A catalyst lowers the activation energy for both the forward and reverse reactions by the same amount. Therefore, it increases the rates of both reactions equally, allowing the system to reach equilibrium faster, but without changing the final equilibrium concentrations (yield). Both statements are correct and R explains A.

This question belongs to: Science chemistry
Question #3
Consider the following statements: 1. A buffer solution resists changes in pH upon adding small amounts of acid or base. 2. A buffer is made of a strong acid and its conjugate base. Which is/are correct?
A. 1 only
B. Neither 1 nor 2
C. Both 1 and 2
D. 2 only

Correct Answer: Option A


Explanation:
A buffer solution maintains a relatively constant pH when small amounts of strong acid or base are added. However, it is typically composed of a weak acid and its conjugate base (or a weak base and its conjugate acid). A strong acid completely dissociates and cannot form a buffer system. Thus, only statement 1 is correct.

This question belongs to: Science chemistry