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Q84 (NDA-II/2012) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Applied everyday chemistry Answer Verified

Given below is an approximate composition of a substance: Ca0-60-70% Si02-20-25% Al20-5-10% Fe203-2-3% The substance is

Result
Your answer: —  Â·  Correct: B
Explanation

The chemical composition provided (CaO: 60-70%, SiO2: 20-25%, Al2O3: 5-10%, and Fe2O3: 2-3%) corresponds to Portland cement. Cement is manufactured by heating a mixture of limestone (calcium carbonate) and clay (containing silica, alumina, and iron oxide) to form clinker. According to technical data, the average oxide composition of Portland clinker typically includes CaO (60-70%), SiO2 (18-22%), Al2O3 (4-6%), and Fe2O3 (2-4%). Other sources confirm that the approximate oxide limits for ordinary Portland cement are CaO (60-67%), SiO2 (17-25%), Al2O3 (3-8%), and Fe2O3 (0.5-6.0%). In contrast, Plaster of Paris is primarily calcium sulfate hemihydrate, marble is a form of calcium carbonate [2], and quartz is nearly pure silicon dioxide. Therefore, the substance described is cement.

Sources

  1. [2] https://jkbose.nic.in/PageDoc/636742059556035861science10th.pdf
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