Properties of Hydrogen
Chapter: Hydrogen | Topic: Properties of Hydrogen
PROPERTIES OF HYDROGEN
Topic: Properties of Hydrogen
Multiple Choice Questions
Q1. Dihydrogen is relatively inert at room temperature because of:
- Its low atomic number
- Its high bond dissociation energy (436 kJ/mol)
- Its low ionisation enthalpy
- Its high electronegativity
Q2. When hydrogen burns in air, the product formed is:
- Hydrogen peroxide
- Water
- Ozone
- Nitric acid
Q3. The reaction of hydrogen with nitrogen to form ammonia is:
- Exothermic and spontaneous at room temperature
- Endothermic and requires high temperature and catalyst
- Exothermic but requires high temperature and catalyst
- A decomposition reaction
Q4. Hydrogen reduces copper oxide to copper. In this reaction, hydrogen acts as:
- An oxidising agent
- A reducing agent
- A catalyst
- An acid
Q5. Which of the following metals does NOT react with dihydrogen to form a hydride?
- Sodium
- Calcium
- Copper
- Magnesium
Q6. The adsorption of hydrogen on metals like platinum and palladium is called:
- Absorption
- Occlusion
- Adsorption
- Chemisorption
Short Answer Questions
Q7. Why does hydrogen not react with most substances at room temperature, despite being a powerful reducing agent at high temperatures?
Q8. Write balanced equations for the reaction of dihydrogen with:
(a) Chlorine
(b) Nitrogen
(c) Copper(II) oxide
Q9. Explain why hydrogen is called a "reducing agent." Give one example where it reduces a metal oxide.
Q10. What happens when dihydrogen is passed over heated sodium metal? Write the equation and name the product formed.
Q11. Your teacher demonstrates that a balloon filled with hydrogen rises up, while one filled with air does not. Explain this observation based on the physical properties of hydrogen.
Q12. Hydrogen reacts with unsaturated hydrocarbons in the presence of a catalyst. What is this reaction called? Give one example with ethene.
Long Answer Questions
Q13. Describe the physical properties of dihydrogen. Why is hydrogen considered the lightest gas? Discuss its solubility, colour, odour, and why it is difficult to liquefy.
Q14. Discuss the chemical properties of dihydrogen under the following headings:
(a) Reaction with halogens
(b) Reaction with dioxygen
(c) Reaction with dinitrogen
(d) Reaction with metal oxides
For each, write the balanced chemical equation and mention the conditions required.
Q15. Hydrogen is used in the hydrogenation of vegetable oils to make vanaspati ghee, a common cooking medium in Indian households. Explain:
(a) The chemical process involved
(b) Why nickel is used as a catalyst
(c) One advantage and one health concern associated with hydrogenated oils
Numerical / Application-Based Problems
Q16. The bond dissociation energy of H–H is 436 kJ/mol. The H–Cl bond energy is 431 kJ/mol.
(a) Calculate the energy required to break 2 moles of H₂ molecules.
(b) Calculate the energy released when 2 moles of HCl are formed from H₂ and Cl₂.
(c) Based on these values, explain why the H–H bond is relatively strong and unreactive at room temperature.
Q17. In the Haber process, 28 g of nitrogen gas reacts with hydrogen.
(a) Write the balanced equation for the formation of ammonia.
(b) Calculate the volume of hydrogen gas required at STP to react completely with 28 g of N₂.
(c) Calculate the mass of ammonia produced.
[Given: Atomic masses: N = 14 u, H = 1 u; Molar volume at STP = 22.4 L]
Q18. A hydrogen-filled balloon used in a school science fair has a volume of 10 L at 25°C and 1 atm pressure. The molar mass of air is approximately 29 g/mol.
(a) Calculate the mass of hydrogen in the balloon.
(b) Calculate the mass of air displaced by the balloon.
(c) Determine the lifting capacity (buoyant force) of the balloon in grams.
[Given: Molar volume at 25°C and 1 atm = 24.5 L, Molar mass of H₂ = 2 g/mol]