All Free Chemistry MCQs with Answers
Every Chemistry question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
13,720 questions · page 477 of 686
- A. B2H6
- B. NH3
- C. H2O
- D. Both B and C
Explanation: Electron-rich hydrides are those where the central atom has one or more lone pairs of electrons after forming bonds with hydrogen.
Correct answer: Both B and C- A. LiH > NaH > CsH > KH > RbH
- B. LiH < NaH < KH < RbH < CsH
- C. RbH > CsH > NaH > KH > LiH
- D. NaH > CsH > RbH > LiH > KH
Explanation: The ionic character of a bond is determined by the difference in electronegativity between the two atoms.
Correct answer: LiH < NaH < KH < RbH < CsH- A. Fluorine
- B. Nitrogen
- C. Carbon
- D. Hydrogen
Explanation: Atomic size generally decreases across a period from left to right due to increasing nuclear charge.
Correct answer: Carbon- A. An oxidizing agent in both (A) and (B)
- B. An oxidizing agent in (A) and a reducing agent in (B)
- C. A reducing agent in (A) and an oxidizing agent in (B)
- D. A reducing agent in both (A) and (B)
Explanation: In reaction (A), H₂O₂ is reduced while oxidizing I⁻ to I₂, so it acts as an oxidizing agent.
Correct answer: An oxidizing agent in (A) and a reducing agent in (B)- A. Liquid hydrogen + liquid oxygen
- B. Liquid oxygen + liquid nitrogen
- C. Both a and b
- D. None of these
Explanation: A rocket propellant requires a fuel and an oxidizer that react to produce a large amount of hot gas for thrust.
Correct answer: Liquid hydrogen + liquid oxygen- A. Reaction of methane with steam
- B. Mixing natural hydrocarbons of high molecular weight
- C. Electrolysis of water
- D. Reaction of ionic hydrides with water
Explanation: The electrolysis of pure water (often containing a small amount of an electrolyte like NaOH or H₂SO₄ to conduct current) produces…
Correct answer: Electrolysis of water9527. Which one of the following noble gases are used for providing an inert atmosphere for welding?
- A. Helium
- B. Neon
- C. Argon
- D. Krypton
Explanation: Argon is chemically inert and does not react with metals at high temperatures.
Correct answer: Argon- A. Hydrogen sulfide
- B. Water
- C. HCl
- D. None of these
Explanation: Hydrogen (H₂) reacts with oxygen during combustion to form H₂O. The reaction is highly exothermic, releasing a lot of energy.
Correct answer: Water- A. H2O
- B. H2S
- C. H2Se
- D. H2Te
Explanation: Boiling points depend on intermolecular forces. H₂O has strong hydrogen bonding, giving it the highest boiling point.
Correct answer: H2S- A. Ca
- B. Cu
- C. Zn
- D. Fe
Explanation: Hydrogen reacts directly with highly reactive metals, such as the alkali and most alkaline earth metals, to form ionic (saline) hydrides.
Correct answer: Ca- A. Si
- B. Ba
- C. Mg
- D. Ca
Explanation: Magnesium (Mg) is the central atom in the chlorophyll molecule. It plays a key role in absorbing light energy during photosynthesis.
Correct answer: Mg- A. Thenard, Urey
- B. Urey, Rutherford
- C. Urey, Thenard
- D. Aston, Chadwick
Explanation: Hydrogen peroxide (H₂O₂) was first isolated and described by Louis Jacques Thénard in 1818.
Correct answer: Thenard, Urey- A. D₂O
- B. H₂O
- C. O₃
- D. Dil. HCl
Explanation: Ozone (O₃) is a powerful oxidizing agent. It can oxidize liquid mercury (Hg), causing it to lose its meniscus and stick to glass, a…
Correct answer: O₃- A. NaNO3
- B. Pb (NO3)2
- C. ZnO
- D. H2O2
Explanation: Hydrogen peroxide (H₂O₂) decomposes upon heating to release O₂. It acts as an oxidizing agent with KI to produce I₂ (brown colour) and as…
Correct answer: H2O2- A. A blue colour is obtained in ether due to formation of Cr2(SO4)3
- B. A blue colour is obtained in ether due to formation of CrO5
- C. A blue colour is obtained in ether due to formation of CrO3
- D. Chromyl chloride is formed
Explanation: This is a characteristic test for chromates. In the presence of acid and H₂O₂, the dichromate ion is converted into chromium(VI) peroxide…
Correct answer: A blue colour is obtained in ether due to formation of CrO5- A. Na, H2, NaOH, Zn
- B. K, H2, KOH, Al
- C. Ca, H2, Ca(OH)2, Sn
- D. CaC2, C2H2, Ca(OH)2
Explanation: The golden yellow flame test identifies A as Sodium (Na). Na reacts with water to produce H₂ gas (B) and NaOH solution (C).
Correct answer: Na, H2, NaOH, Zn- A. Na+ and K+
- B. Ca2+ and Mg2+
- C. Ca2+ and K+
- D. Ca2+ and Na+
Explanation: Hardness in water is primarily caused by the presence of dissolved divalent cations, specifically calcium (Ca²⁺) and magnesium (Mg²⁺)…
Correct answer: Ca2+ and Mg2+- A. Be(OH)2
- B. Mg(OH)2
- C. B(OH)3
- D. Al(OH)3
Explanation: Boric acid, B(OH)₃, is a weak Lewis acid, accepting an OH⁻ ion from water rather than donating a proton.
Correct answer: B(OH)3- A. Reduce the silver bromide grains to metallic silver
- B. Convert the metallic silver to silver salt
- C. Remove undecomposed AgBr as soluble silver thiosulphate complex
- D. Remove reduced silver
Explanation: In the photographic fixing process, sodium thiosulfate (hypo) is used to remove the unexposed and undeveloped silver bromide (AgBr) from…
Correct answer: Remove undecomposed AgBr as soluble silver thiosulphate complex- A. Ammoniated complex cation
- B. Ammoniated electrons
- C. d-d transition
- D. Both (a) & (b)
Explanation: When alkali or alkaline earth metals dissolve in liquid ammonia, they release their valence electrons, which become solvated by the…
Correct answer: Ammoniated electrons