Effects of Oxidation Corrosion Rancidity - UNSOLVED PRACTICE SET

Q7. Define corrosion and rancidity. Give one example of each from daily life.

Q8. Write the chemical formula of rust. What are the conditions necessary for the rusting of iron?

Q9. Your grandmother stores leftover fried snacks in airtight containers. She also adds a small pouch containing silica gel. Explain how these measures prevent rancidity.

Q10. List any four methods to prevent rusting of iron. Explain the principle behind any one method.

Q11. Why does food with oil and fat become rancid when kept for a long time? Name two antioxidants commonly added to food to prevent rancidity.

Q12. Why do silver articles turn black when exposed to air for a long time? Write the chemical equation involved.

Q13. Define corrosion and explain the process of rusting of iron with a chemical equation. What are the necessary conditions for rusting? Describe at least four methods to prevent rusting and explain the scientific principle behind each method.

Q14. A student observes the following in her kitchen and home:

Observation 1: Iron gate in the garden has reddish-brown patches

Observation 2: Potato chips in an open packet taste bitter after a week

Observation 3: Silver anklets turn black

Observation 4: Copper vessel used for storing water develops a green coating

(a) Identify the chemical process responsible for each observation.

(b) Write chemical equations for Observations 1, 3, and 4.

(c) Suggest preventive measures for each observation.

(d) Why does the iron gate rust faster during the monsoon season in India?

(e) Explain why nitrogen flushing is used for potato chips but not for iron gates.

Q15. "Corrosion and rancidity are both destructive effects of oxidation, but they affect metals and food differently. Understanding them helps us save money, preserve food, and protect infrastructure." Discuss this statement by explaining: (i) the economic impact of corrosion on Indian infrastructure, (ii) health implications of consuming rancid food, (iii) traditional and modern methods of preventing rancidity in Indian households, and (iv) government initiatives to protect monuments and bridges from corrosion.

Q16. A construction company in Mumbai needs to protect iron pillars used in a coastal bridge from corrosion.

(a) Write the chemical equation for the rusting of iron.

(b) If each iron pillar weighs 2 tonnes and the company installs 100 pillars, calculate the total mass of iron.

(c) If 2% of the iron rusts annually in the coastal environment, calculate the mass of rust formed per year. (Assume rust is Fe₂O₃·3H₂O, molar mass = 214 g/mol; Fe = 56 g/mol)

(d) The company decides to galvanize the pillars with a 3% zinc coating by mass. Calculate the mass of zinc needed for all pillars.

(e) Why is galvanization particularly effective in coastal areas compared to painting?

Q17. A food processing company in India manufactures packaged snacks and cooking oils.

(a) The company packs 50,000 packets of potato chips daily. If each packet contains 50 g of chips and nitrogen flushing costs ₹0.10 per packet, calculate the daily cost of nitrogen flushing.

(b) The company uses BHT (butylated hydroxytoluene) as an antioxidant in cooking oil. If 0.02% BHT by mass is added to 10,000 litres of oil (density = 0.9 g/mL), calculate the mass of BHT added.

(c) A batch of 1000 kg of groundnut oil becomes rancid, causing a loss of ₹200 per kg. Calculate the total financial loss.

(d) Suggest three methods the company can use to prevent rancidity in oil, other than adding antioxidants.

(e) If the company stores oil in stainless steel containers instead of iron containers, how does this prevent rancidity?
(Hint: Think about catalysis)

Q18. The Indian Railways maintains thousands of kilometres of track across diverse climates — from the humid coasts of Kerala to the dry deserts of Rajasthan.

(a) Write the chemical equation for the rusting of iron tracks.

(b) If a 1 km stretch of track contains 500 tonnes of iron, and the annual rusting rate is 1% in coastal Kerala and 0.3% in dry Rajasthan, calculate the mass of rust formed annually in each location.

(c) The Railways spends approximately ₹10,000 per tonne to replace rusted track. Calculate the annual replacement cost for the 1 km stretch in each location.

(d) The Railways uses a combination of painting, greasing, and alloy steel to prevent corrosion. Explain the principle behind each method.

(e) If India has 68,000 km of railway track and the average rusting rate is 0.5%, calculate the total annual economic loss due to corrosion. (Assume replacement cost of ₹10,000 per tonne, 500 tonnes iron per km)