Q. 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
Correct Answer : (b) Both Statement II and Statement III are correct but only one of them explains Statement I
UPSC Prelims 2025 GS Paper's Solution
Explanation :
Statement I is true – cement manufacture is responsible for roughly 5–7 % of global CO₂ emissions.
Statement II is true – Portland‐cement “raw meal” is typically made by grinding together about 80 % limestone (CaCO₃) with 20 % silica-bearing clays and other minor additives.
Statement III is true – in the kiln the limestone is calcined: CaCO₃ → CaO + CO₂↑
Of the two, only Statement III explains the CO₂ emissions in Statement I (the chemical decomposition of CaCO₃ releases CO₂). Statement II describes the raw‐material blend but does not itself generate CO₂. Hence both II and III are correct, but only III explains I.
