Which of the following reactions is a double displacement reaction?
A. BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl
B. Zn + H₂SO₄ → ZnSO₄ + H₂
C. 2Mg + O₂ → 2MgO
D. CaCO₃ → CaO + CO₂
Answer: Option A
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.
Explanation:
Ernest Rutherford is generally credited with the discovery of the proton in 1919 through the nuclear reaction: ¹⁴N + α particle → ¹⁷O + proton. Eugen Goldstein earlier observed canal rays (positive rays) which were later identified as protons by Rutherford. Thomson discovered electron, Chadwick neutron. So Rutherford is the accepted discoverer.
Explanation:
Ant sting contains formic acid (methanoic acid, HCOOH). It causes a burning sensation. It can be neutralized by applying a mild base like baking soda. Acetic acid is in vinegar, citric acid in lemons, lactic acid in curd.
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