Q1: What is the molecular formula of sulphuric acid? (a) H₂SO₃ (b) H₂SO₄ (c) H₂S₂O₇ (d) HSO₄
Solution:
Ans: (b) Explanation: Sulphuric acid has the molecular formula H₂SO₄, with a relative molecular mass of 98. This is the standard chemical formula for this strong acid.
Q2: Which catalyst is used in the catalytic oxidation of sulphur dioxide to sulphur trioxide in the contact process? (a) Platinum (b) Iron oxide (c) Vanadium pentaoxide (d) Nickel
Solution:
Ans: (c) Explanation: Vanadium pentaoxide acts as the catalyst during the oxidation of SO₂ to SO₃ at 450°C in the contact process for manufacturing sulphuric acid.
Q3: What is the boiling point of sulphuric acid? (a) 100°C (b) 338°C (c) 450°C (d) 212°C
Solution:
Ans: (b) Explanation: Sulphuric acid has a boiling point of 338°C and a melting point of 10.4°C. This high boiling point makes it a non-volatile acid.
Q4: When concentrated sulphuric acid reacts with copper, which gas is produced? (a) Hydrogen (b) Oxygen (c) Carbon dioxide (d) Sulphur dioxide
Solution:
Ans: (d) Explanation: Concentrated sulphuric acid acts as an oxidising agent with copper producing copper sulphate, water and sulphur dioxide gas according to the reaction Cu + 2H₂SO₄ → CuSO₄ + 2H₂O + SO₂.
Q5: What is oleum? (a) Dilute sulphuric acid (b) Sulphur trioxide (c) Pyrosulphuric acid (d) Hydrogen sulphide
Solution:
Ans: (c) Explanation: Oleum, also known as pyrosulphuric acid with formula H₂S₂O₇, is formed when sulphur trioxide vapours are absorbed by concentrated sulphuric acid in the contact process.
Fill in the Blanks
Q1: The relative molecular mass of sulphuric acid is _____.
Solution:
Ans: 98
Q2: In the contact process, sulphur dioxide is produced by roasting metallic _____ in air.
Solution:
Ans: sulphides
Q3: Sulphuric acid is _____ than water.
Solution:
Ans: heavier
Q4: Concentrated sulphuric acid acts as a _____ agent due to its great affinity for water.
Solution:
Ans: dehydrating
Q5: The temperature at which catalytic oxidation of sulphur dioxide occurs in the contact process is _____°C.
Solution:
Ans: 450
True or False
Q1: Sulphuric acid is colourless, odourless and has a slight sour taste.
Solution:
Ans: True Explanation: Sulphuric acid is indeed colourless and odourless with a slight sour taste, and it is highly corrosive in nature.
Q2: Dilute sulphuric acid reacts with metals to produce oxygen gas.
Solution:
Ans: False Explanation: Dilute sulphuric acid reacts with metals to form metallic sulphate and hydrogen gas, not oxygen gas.
Q3: Concentrated sulphuric acid can be used to prepare volatile acids from their salts.
Solution:
Ans: True Explanation: Due to its non-volatile nature and high boiling point, concentrated sulphuric acid prepares volatile acids like HCl and HNO₃ from salts.
Q4: When sulphuric acid reacts with metal carbonates, hydrogen sulphide is liberated.
Solution:
Ans: False Explanation: Sulphuric acid liberates carbon dioxide from metallic carbonates and bicarbonates, not hydrogen sulphide which comes from metal sulphides.
Q5: Sulphuric acid is used in the pickling of metals to remove metallic impurities before galvanising.
Solution:
Ans: True Explanation: Pickling of metals using sulphuric acid removes metallic impurities from the surface of metals before the galvanising process.
Match the Following
Column A
Column B
1. Oleum
A. Hydrogen gas
2. Reaction of dilute H₂SO₄ with metals
B. 450°C
3. Catalytic oxidation temperature
C. Dehydrating agent
4. Great affinity for water
D. H₂S₂O₇
5. Relative molecular mass of H₂SO₄
E. 98
Solution:
Ans:
1 - D: Oleum is also known as pyrosulphuric acid with the chemical formula H₂S₂O₇, formed during the contact process.
2 - A: Dilute sulphuric acid reacts with metals like magnesium and iron to form metallic sulphate and hydrogen gas.
3 - B: The catalytic oxidation of sulphur dioxide to sulphur trioxide occurs at a temperature of 450°C using vanadium pentaoxide.
4 - C: Concentrated sulphuric acid has great affinity for water and therefore acts as a powerful dehydrating agent for various compounds.
5 - E: The relative molecular mass of sulphuric acid (H₂SO₄ ) is 98, calculated from its constituent atomic masses.
Short Answer Questions
Q1: Describe the four steps involved in the contact process for the manufacture of sulphuric acid.
Solution:
Ans: The contact process involves four steps. First, sulphur dioxide is produced by roasting metallic sulphides in air. Second, impurities are removed from the gas mixture to enhance catalyst efficiency. Third, sulphur dioxide is catalytically oxidised to sulphur trioxide at 450°C using vanadium pentaoxide. Finally, sulphur trioxide is absorbed in concentrated sulphuric acid to form oleum, which is then diluted with water to obtain sulphuric acid.
Q2: Explain how concentrated sulphuric acid acts as a dehydrating agent with suitable examples.
Solution:
Ans: Concentrated sulphuric acid has great affinity for water, making it an effective dehydrating agent. It removes water molecules from substances. For example, when ethanol is treated with concentrated sulphuric acid, it dehydrates to form ethene by removing water. Similarly, glucose dehydrates to form carbon by removing water molecules. These reactions demonstrate sulphuric acid's ability to extract water from organic compounds chemically.
Q3: How does dilute sulphuric acid react with metallic carbonates and metal sulphides? Give one example of each.
Solution:
Ans: Dilute sulphuric acid liberates carbon dioxide from metallic carbonates and bicarbonates. For example, sodium carbonate reacts with dilute sulphuric acid to form sodium sulphate, water and carbon dioxide. With metal sulphides, it evolves hydrogen sulphide gas. For instance, zinc sulphide reacts with dilute sulphuric acid to produce zinc sulphate and hydrogen sulphide gas. Both reactions involve displacement of weaker acids by sulphuric acid.
Q4: What are the physical properties of sulphuric acid?
Solution:
Ans: Sulphuric acid is colourless and odourless with a slight sour taste. It is highly corrosive in nature and chars the skin black upon contact. The acid is heavier than water and completely soluble in water. It has a high boiling point of 338°C and a melting point of 10.4°C. These properties make it a stable, non-volatile acid useful in various industrial applications.
Q5: Describe the uses of sulphuric acid in industrial applications.
Solution:
Ans: Sulphuric acid has numerous industrial applications. It is used in manufacturing fertilisers such as ammonium sulphate and superphosphate of lime, essential for agriculture. The acid is employed in preparing explosives like trinitrotoluene and picric acid. It is crucial in metal extraction through leaching processes and in pickling metals to remove impurities before galvanising. Additionally, it is used to prepare various gases including halogens, carbon monoxide and sulphur dioxide.
Long Answer Questions
Q1: Compare the properties of dilute and concentrated sulphuric acid. Justify why concentrated sulphuric acid is preferred for preparing volatile acids from their salts.
Solution:
Ans: Dilute sulphuric acid reacts with metals to form metallic sulphates and liberate hydrogen gas. For example: Mg + H₂SO₄ → MgSO₄ + H₂ It also neutralises bases and reacts with metallic carbonates to release carbon dioxide. Concentrated sulphuric acid shows different properties. It acts as a strong oxidising agent and reacts with copper to form copper sulphate with the liberation of sulphur dioxide: Cu + 2H₂SO₄ → CuSO₄ + 2H₂O + SO₂ It also acts as a powerful dehydrating agent due to its strong affinity for water. Concentrated sulphuric acid is preferred for preparing volatile acids such as hydrochloric acid and nitric acid from their salts because of its non-volatile nature and high boiling point. For example: NaCl + H₂SO₄ → NaHSO₄ + HCl
Q2: Analyse the role of the catalyst and temperature in the contact process for manufacturing sulphuric acid. Evaluate why purification of gases is essential.
Solution:
Ans: In the contact process, vanadium pentaoxide acts as the catalyst for oxidising sulphur dioxide to sulphur trioxide at 450°C. This specific temperature and catalyst combination ensures optimal conversion efficiency. The catalyst provides an alternative reaction pathway with lower activation energy, speeding up the reaction without being consumed. Purification of gases before catalytic oxidation is essential because impurities can poison or deactivate the catalyst surface, significantly reducing its efficiency. Clean gases ensure maximum contact with the catalyst surface, leading to better conversion rates and higher yield of sulphur trioxide, which ultimately produces pure sulphuric acid of desired concentration.
Q3: Evaluate the various chemical properties of concentrated sulphuric acid and explain how its oxidising and dehydrating nature makes it useful in different applications.
Solution:
Ans: Concentrated sulphuric acid exhibits three key chemical properties. As a non-volatile acid with high boiling point, it displaces volatile acids from their salts. As an oxidising agent, it oxidises metals like copper and non-metals like carbon, producing sulphur dioxide. As a dehydrating agent, it removes water from organic compounds like ethanol and glucose due to its strong affinity for water. These properties make it industrially valuable: its oxidising nature helps in metal extraction processes, its dehydrating property is used in organic synthesis, and its non-volatile nature allows preparation of other acids. This versatility makes sulphuric acid indispensable in fertiliser manufacturing, explosives production and metal processing industries.
The document Worksheet with Solutions: Study of Compounds – Sulphuric Acid is a part of the Class 10 Course Chemistry Class 10 ICSE.
FAQs on Worksheet with Solutions: Study of Compounds – Sulphuric Acid
1. What is sulphuric acid and what are its main uses?
Ans. Sulphuric acid (H₂SO₄) is a colourless, odourless, and highly corrosive strong mineral acid. Its main uses include the production of fertilisers, the manufacture of chemicals, petroleum refining, and metal processing. It is also used in batteries and for dehydrating substances due to its strong hygroscopic nature.
2. What are the physical properties of sulphuric acid?
Ans. Sulphuric acid is a dense, viscous liquid with a boiling point of about 337 °C and a melting point of approximately 10 °C. It is highly soluble in water, releasing heat upon dilution. The acid is non-volatile and can cause severe burns upon contact with skin.
3. How is sulphuric acid produced industrially?
Ans. Sulphuric acid is produced primarily through the Contact Process, which involves the oxidation of sulphur dioxide (SO₂) to sulphur trioxide (SO₃) using vanadium(V) oxide as a catalyst. The SO₃ is then dissolved in water to form sulphuric acid, ensuring that the process is efficient and cost-effective.
4. What safety precautions should be taken when handling sulphuric acid?
Ans. When handling sulphuric acid, it is essential to wear appropriate personal protective equipment, including gloves, goggles, and lab coats. Work should be conducted in a well-ventilated area or a fume hood to avoid inhaling fumes. In case of contact with skin or eyes, it is crucial to rinse immediately with plenty of water and seek medical attention.
5. What are the environmental impacts of sulphuric acid?
Ans. The environmental impacts of sulphuric acid include its potential to cause acid rain, which can damage ecosystems, soil, and water bodies. It can also lead to soil degradation and adversely affect plant life. Proper management and regulation are necessary to mitigate these effects and protect the environment.
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