Q81. Hydrogen reacts with metals to form:
A) Salts
B) Hydrides
C) Acids
D) Oxides
Answer: B) Hydrides
Explanation: Hydrogen reacts with metals to form metal hydrides like NaH and CaH₂.
Q82. The oxidation state of hydrogen in ammonia (NH₃) is:
A) +1
B) 0
C) -1
D) +2
Answer: A) +1
Explanation: In ammonia (NH₃), hydrogen has an oxidation state of +1 as it is bonded to a more electronegative element, nitrogen.
Q83. The most abundant isotope of hydrogen in nature is:
A) Protium
B) Deuterium
C) Tritium
D) None of the above
Answer: A) Protium
Explanation: Protium (¹H) is the most abundant isotope of hydrogen, making up over 99% of naturally occurring hydrogen.
Q84. In which of the following hydrides does hydrogen have the oxidation state of -1?
A) H₂O
B) HCl
C) NaH
D) CH₄
Answer: C) NaH
Explanation: In sodium hydride (NaH), hydrogen has an oxidation state of -1 because it gains an electron from sodium.
Q85. Which of the following reactions is used for the preparation of hydrogen gas?
A) Ca + H₂O → Ca(OH)₂ + H₂
B) NaOH + HCl → NaCl + H₂O
C) ZnO + H₂ → Zn + H₂O
D) CO + H₂O → CO₂ + H₂
Answer: D) CO + H₂O → CO₂ + H₂
Explanation: This is the water-gas shift reaction, used for hydrogen production, where carbon monoxide reacts with steam to form carbon dioxide and hydrogen.
Q86. Which of the following is not a property of hydrogen?
A) It is highly inflammable.
B) It is denser than air.
C) It has high diffusibility.
D) It has high energy content.
Answer: B) It is denser than air.
Explanation: Hydrogen is much less dense than air, making this statement incorrect.
Q87. The reaction of sodium with water produces:
A) Sodium oxide and hydrogen
B) Sodium hydroxide and hydrogen
C) Sodium chloride and hydrogen
D) Sodium peroxide and hydrogen
Answer: B) Sodium hydroxide and hydrogen
Explanation: Sodium reacts with water to form sodium hydroxide and hydrogen gas.
Q92. Hydrogen behaves as a metal in:
A) Solid state
B) Gaseous state
C) Liquid state
D) Plasma state
Answer: A) Solid state
Explanation: Under extreme pressure, hydrogen can exhibit metallic properties in its solid state.
Q93. Which of the following statements is correct about the reaction of hydrogen with alkali metals?
A) Hydrogen forms covalent bonds with alkali metals.
B) Hydrogen forms ionic hydrides with alkali metals.
C) Hydrogen forms hydrogen bonds with alkali metals.
D) Hydrogen forms metallic bonds with alkali metals.
Answer: B) Hydrogen forms ionic hydrides with alkali metals.
Explanation: Hydrogen forms ionic hydrides (e.g., NaH, LiH) with alkali metals, where hydrogen exists as a hydride ion (H⁻).
Q94. Which of the following statements is true about the reaction of hydrogen with oxygen?
A) It requires high temperature to proceed.
B) It is a slow process at room temperature.
C) It is highly exothermic.
D) It produces ozone.
Answer: C) It is highly exothermic.
Explanation: The reaction between hydrogen and oxygen is highly exothermic and releases a large amount of energy, forming water.
Q95. Which of the following is a feature of metallic hydrides?
A) They are good conductors of electricity.
B) They are molecular in nature.
C) They are ionic compounds.
D) They are formed by s-block elements only.
Answer: A) They are good conductors of electricity.
Explanation: Metallic hydrides, especially those formed by transition metals, can conduct electricity due to the presence of free electrons.
Q96. Which property of hydrogen is utilized in the hydrogenation of oils?
A) Reducing property
B) Oxidizing property
C) Acidity
D) Basicity
Answer: A) Reducing property
Explanation: In the hydrogenation of oils, hydrogen reduces the double bonds in unsaturated fats, converting them into saturated fats.
Q97. Hydrogen gas burns in air with a:
A) Blue flame
B) Green flame
C) Pale blue flame
D) Yellow flame
Answer: C) Pale blue flame
Explanation: Hydrogen burns in air with a pale blue flame, producing water vapor.
Q98. In which of the following reactions does hydrogen act as an oxidizing agent?
A) H₂ + O₂ → H₂O
B) H₂ + CO → CH₃OH
C) H₂ + N₂ → NH₃
D) H₂ + Na → NaH
Answer: D) H₂ + Na → NaH
Explanation: In this reaction, hydrogen accepts an electron from sodium and thus acts as an oxidizing agent.
Q99. The dissolution of hydrogen gas in metals is an example of:
A) Physical adsorption
B) Chemisorption
C) Interstitial solution
D) Sublimation
Answer: C) Interstitial solution
Explanation: Hydrogen atoms occupy interstitial sites in the metal lattice, forming an interstitial solution.
Q100. Which of the following is true about the isotopes of hydrogen?
A) All isotopes of hydrogen are radioactive.
B) Deuterium and tritium are stable isotopes.
C) Tritium is radioactive, while protium and deuterium are stable.
D) Only protium is radioactive.
Answer: C) Tritium is radioactive, while protium and deuterium are stable.
Explanation: Tritium (³H) is radioactive, whereas protium (¹H) and deuterium (²H) are stable isotopes of hydrogen.
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