Q1: What is the molecular formula of nitric acid? (a) HNO2 (b) HNO3 (c) H2NO3 (d) HN2O3
Solution:
Ans: (b) Explanation: Nitric acid has the molecular formula HNO3, containing one hydrogen atom, one nitrogen atom, and three oxygen atoms with a relative molecular mass of 63.
Q2: What is the boiling point of nitric acid? (a) 42°C (b) 63°C (c) 86°C (d) 98°C
Solution:
Ans: (c) Explanation: Nitric acid has a boiling point of 86°C. It also has a freezing point of -42°C and a specific gravity of 1.54, making it heavier than water.
Q3: Which gas is produced when nitric acid reacts with sodium carbonate? (a) Oxygen (b) Nitrogen dioxide (c) Carbon dioxide (d) Nitric oxide
Solution:
Ans: (c) Explanation: When nitric acid reacts with carbonates like sodium carbonate, it produces salt, water, and carbon dioxide gas according to the reaction: Na2CO3 + 2HNO3 → 2NaNO3 + H2O + CO2.
Q4: What is aqua regia composed of? (a) Nitric acid and sulphuric acid (b) Nitric acid and hydrochloric acid (c) Hydrochloric acid and sulphuric acid (d) Nitric acid and phosphoric acid
Solution:
Ans: (b) Explanation: Aqua regia is formed by mixing concentrated nitric acid (1 part by volume) with concentrated hydrochloric acid (3 parts by volume). It contains nascent chlorine and dissolves noble metals.
Q5: Which gas is liberated when concentrated nitric acid reacts with copper? (a) Oxygen (b) Nitric oxide (c) Nitrogen dioxide (d) Carbon dioxide
Solution:
Ans: (c) Explanation: Concentrated nitric acid reacts with copper to produce copper nitrate, water, and nitrogen dioxide gas according to the reaction: Cu + 4HNO3 → Cu(NO3)2 + 2H2O + 2NO2.
Fill in the Blanks
Q1: The relative molecular mass of nitric acid is _____.
Solution:
Ans: 63
Q2: Pure nitric acid has a specific gravity of _____.
Solution:
Ans: 1.54
Q3: Nitric acid is a very strong _____ acid.
Solution:
Ans: monobasic
Q4: When nitric acid reacts with alkalis, it produces salt and _____.
Solution:
Ans: water
Q5: Nitric acid oxidises sulphur to _____ acid.
Solution:
Ans: sulphuric
True or False
Q1: Pure nitric acid is colourless and stable at room temperature.
Solution:
Ans: False Explanation: Pure nitric acid is colourless but unstable, decomposing slightly even at room temperature and in the presence of sunlight into nitrogen dioxide, water, and oxygen.
Q2: The freezing point of nitric acid is -42°C.
Solution:
Ans: True Explanation: Nitric acid has a freezing point of -42°C and a boiling point of 86°C, making it a liquid at room temperature under normal conditions.
Q3: Cold and dilute nitric acid liberates nitrogen dioxide when reacting with metals.
Solution:
Ans: False Explanation: Cold and dilute nitric acid liberates nitric oxide, not nitrogen dioxide. Concentrated nitric acid liberates nitrogen dioxide when reacting with metals like copper and zinc.
Q4: Aqua regia can dissolve noble metals such as gold and platinum.
Solution:
Ans: True Explanation: Aqua regia contains nascent chlorine which reacts with noble metals like gold and platinum to produce their chlorides, effectively dissolving these resistant metals.
Q5: Nitric acid neutralises alkalis to form salt and carbon dioxide.
Solution:
Ans: False Explanation: Nitric acid neutralises alkalis to form salt and water only. Carbon dioxide is produced when nitric acid reacts with carbonates and bicarbonates, not alkalis.
Match the Following
Column A
Column B
1. Molecular formula of nitric acid
A. 86°C
2. Specific gravity of pure nitric acid
B. Nascent chlorine
3. Boiling point of nitric acid
C. HNO3
4. Active component in aqua regia
D. 1.54
5. Gas liberated by dilute nitric acid with metals
E. Nitric oxide
Solution:
Ans:
1 - C: Nitric acid has the molecular formula HNO3, consisting of hydrogen, nitrogen, and three oxygen atoms with a relative molecular mass of 63.
2 - D: Pure nitric acid has a specific gravity of 1.54, making it heavier than water which has a specific gravity of approximately 1.0.
3 - A: Nitric acid boils at 86°C and freezes at -42°C, remaining liquid at room temperature under normal conditions with colourless appearance.
4 - B: Aqua regia contains nascent chlorine which is responsible for dissolving noble metals like gold and platinum by forming their respective chlorides.
5 - E: Cold and dilute nitric acid oxidises metals to their nitrates and liberates nitric oxide gas, not nitrogen dioxide which comes from concentrated acid.
Short Answer Questions
Q1: Describe the physical properties of pure nitric acid.
Solution:
Ans: Pure nitric acid is 98% concentrated and appears colourless with a suffocating odour and sour taste. It is heavier than water with a specific gravity of 1.54. Its boiling point is 86°C whilst the freezing point is -42°C. Despite being pure, it is unstable and decomposes slightly even at room temperature.
Q2: Explain the reaction of nitric acid with carbonates and bicarbonates.
Solution:
Ans: Nitric acid reacts with carbonates and bicarbonates to produce salt, water, and carbon dioxide gas. For example, sodium carbonate reacts with nitric acid to form sodium nitrate, water, and carbon dioxide: Na2CO3 + 2HNO3 → 2NaNO3 + H2O + CO2. Similarly, sodium bicarbonate reacts: NaHCO3 + HNO3 → NaNO3 + H2O + CO2.
Q3: How does nitric acid oxidise non-metals like carbon, sulphur, and phosphorus?
Solution:
Ans: Nitric acid oxidises non-metals to their highest oxides or oxy-acids. Carbon is oxidised to carbon dioxide, sulphur to sulphuric acid, and phosphorus to phosphoric acid. The reactions are: C + 4HNO3 → 2H2O + 4NO2 + CO2, S + 6HNO3 → H2SO4 + 2H2O + 6NO2, and P4 + 20HNO3 → 4H3PO4 + 4H2O + 20NO2.
Q4: What is aqua regia and how is it prepared?
Solution:
Ans: Aqua regia is a powerful mixture produced by mixing concentrated nitric acid (1 part by volume) with concentrated hydrochloric acid (3 parts by volume). The reaction produces: HNO3 + 3HCl → NOCl + 2H2O + 2[Cl]. It contains nascent chlorine which can dissolve noble metals like gold and platinum by forming their chlorides.
Q5: List four important uses of nitric acid in industry and daily life.
Solution:
Ans: Nitric acid has several important uses: It etches designs on copper and brassware by acting as a solvent for metals. It purifies gold by dissolving impurities like copper, silver, and zinc. It serves as a rocket fuel oxidant. It is used in preparing fertilisers such as calcium nitrate and ammonium nitrate, and in making aqua regia.
Long Answer Questions
Q1: Analyse the difference between the reactions of cold dilute nitric acid and concentrated nitric acid with metals like copper and zinc.
Solution:
Ans: Cold and dilute nitric acid oxidises metals such as copper and zinc to their nitrates and liberates nitric oxide (NO). In these reactions, nitric acid acts as an oxidising agent and the metal is converted into its nitrate. In contrast, concentrated nitric acid liberates nitrogen dioxide instead of nitric oxide: Cu + 4HNO₃ → Cu(NO₃)₂ + 2H₂O + 2NO₂ and Zn + 4HNO₃ → Zn(NO₃)₂ + 2H₂O + 2NO₂. The key difference lies in the concentration affecting which nitrogen oxide gas is produced. Thus, the main difference between the reactions of dilute and concentrated nitric acid with metals lies in the nature of the nitrogen oxide gas evolved. Dilute nitric acid produces nitric oxide (NO), whereas concentrated nitric acid produces nitrogen dioxide (NO₂). This difference occurs due to the higher oxidising power of concentrated nitric acid.
Q2: Evaluate why nitric acid is considered both a strong acid and a powerful oxidising agent with suitable examples.
Solution:
Ans: Nitric acid is a very strong monobasic acid because it ionises almost completely in aqueous solution: HNO3 ⇌ H+ + NO3-. It neutralises alkalis forming salts: CaO + 2HNO3 → Ca(NO3)2 + H2O. As a powerful oxidising agent, it oxidises non-metals to their highest oxides, converting carbon to carbon dioxide, sulphur to sulphuric acid, and phosphorus to phosphoric acid. It also oxidises metals to their nitrates, liberating nitrogen oxides. This dual nature makes it highly reactive and industrially valuable.
Q3: Justify the importance of aqua regia in metallurgy and explain its chemical composition and action on noble metals.
Solution:
Ans: Aqua regia is crucial in metallurgy for dissolving noble metals which are otherwise chemically resistant. It is prepared by mixing concentrated nitric acid (1 part) with concentrated hydrochloric acid (3 parts): HNO3 + 3HCl → NOCl + 2H2O + 2[Cl]. The nascent chlorine produced is highly reactive and attacks noble metals like platinum and gold: Pt + 4[Cl] → PtCl4 and Au + 3[Cl] → AuCl3. This property makes aqua regia essential for purifying gold and recovering precious metals from electronic waste and jewellery.
The document Worksheet with Solutions: Study of Compounds - Ammonia and Nitric Acid is a part of the Class 10 Course Chemistry Class 10 ICSE.
FAQs on Worksheet with Solutions: Study of Compounds - Ammonia and Nitric Acid
1. What is the chemical formula for ammonia?
Ans. The chemical formula for ammonia is NH₃.
2. How is nitric acid commonly produced?
Ans. Nitric acid is commonly produced through the Ostwald process, which involves the oxidation of ammonia to nitrogen monoxide, followed by the oxidation of nitrogen monoxide to nitrogen dioxide, which is then absorbed in water to form nitric acid.
3. What are the primary uses of ammonia in industry?
Ans. Ammonia is primarily used in the production of fertilisers, as a refrigerant, and in the manufacturing of various chemicals, including nitric acid and urea.
4. What is the pH nature of ammonia when dissolved in water?
Ans. When ammonia is dissolved in water, it forms a basic solution, typically with a pH greater than 7, due to the formation of ammonium hydroxide (NH₄OH).
5. Why is nitric acid considered a strong acid?
Ans. Nitric acid is considered a strong acid because it completely dissociates in water, releasing a high concentration of hydrogen ions (H⁺), which contributes to its strong acidic properties.
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