निम्नलिखित कथनों पर विचार कीजिए :
- कथन I: अध्ययनों से सूचित होता है कि सीमेंट उद्योग से उत्सर्जित कार्बन डाइऑक्साइड का वैश्विक कार्बन उत्सर्जन में उसके 5% से अधिक का योगदान है।
- कथन II: सीमेंट का निर्माण करते समय चूना-पत्थर में सिलिका-युक्त मृत्तिका मिलाई जाती है।
- कथन III: सीमेंट निर्माण हेतु क्लिंकर उत्पादन के दौरान चूना-पत्थर, चूना में बदल जाता है।
उपर्युक्त कथनों के बारे में, निम्नलिखित में से कौन-सा एक सही है?
Read this question in English
Consider the following statements:
Statement I. Studies indicate that carbon dioxide emissions from cement industry account for more than 5% of global carbon emissions.
Statement II. Silica-bearing clay is mixed with limestone while manufacturing cement.
Statement III. Limestone is converted into lime during clinker production for cement manufacturing.
Which one of the following is correct in respect of the above statements?
(a) Both Statement II and Statement III are correct and both of them explain Statement I · (b) Both Statement II and Statement III are correct but only one of them explains Statement I · (c) Only one of the Statements II and III is correct and that explains Statement I · (d) Neither Statement II nor Statement III is correct
उत्तर और व्याख्या · explanation in English
Answer: (b) कथन II और कथन III दोनों सही हैं किन्तु उनमें से केवल एक, कथन I की व्याख्या करता है
Cement is among the largest single industrial sources of carbon dioxide, about 7% of global emissions according to the International Energy Agency. Both manufacturing facts are true, but only Statement III explains the emissions: heating limestone (calcium carbonate) to make lime releases carbon dioxide directly, on top of the fuel burnt in the kiln. Mixing silica-bearing clay with limestone is simply part of the recipe.
- ✓ Statement I The International Energy Agency puts the cement sector's share of global carbon dioxide emissions at about 7%, which is well above 5%.
- ✓ Statement II Cement needs limestone plus silica and alumina, which come mainly from clay or shale; this is true but does not by itself produce the carbon dioxide.
- ✓ Statement III In the kiln, calcium carbonate breaks down into calcium oxide (lime) and carbon dioxide; this 'process emission' is the main reason cement is so carbon-intensive, so III explains I.
Remember · Cement CO2 is about 7% of global emissions (IEA); most comes from calcination (CaCO3 → CaO + CO2) in clinker making, the rest from kiln fuel.
📘 Read it in NCERT: Class 10 Science, Ch 1 (practise this chapter) · Class 10 Contemporary India – II, Ch 6 (practise this chapter)
Sources
- International Energy Agency: Cement technology roadmap plots path to cutting CO2 emissions 24% by 2050 (copy of the IEA news page) ↗ “The cement sector is the third-largest industrial energy consumer in the world, responsible for 7% of industrial energy use, and the second industrial emitter of carbon dioxide, with about 7% of global emissions.”
- NCERT Class 10 · Science, Chapter 1 “Decomposition of calcium carbonate to calcium oxide and carbon dioxide on heating is an important decomposition reaction used in various industries. Calcium oxide is called lime or quick lime. It has many uses – one is in the manufacture of cement.”
- NCERT Class 10 · Contemporary India – II, Chapter 6 “This industry requires bulky and heavy raw materials like limestone, silica and gypsum.”
Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·