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UPSC 1999: Consider the following statements: I. Glass can be etched or scratched by diamond. II. Glass can be etched or scratched by hydrofluoric acid. III. Glass can be etched or scratched by aqua regia. IV. Glass can be etched or scratched by concentrated sulphuric acid. Which of these statements are correct?
(a)I and IV
(b)II and III
(c)I and II
(d)II and IV
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Not attemptedCorrect Answer: (c) I and II
Diamond, harder than glass, can mechanically scratch it (I). Hydrofluoric acid chemically etches silica glass (II). Aqua regia and concentrated H₂SO₄ do not appreciably attack ordinary glass, so III and IV are false. Thus statements I and II only are correct, giving option (c).
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Frequently Asked Questions
What is the correct answer to this UPSC 1999 Science & Technology question?▼
The correct answer is option (c): I and II. Watch the detailed video explanation in our Sherlocking Prelims course on UnlockIAS.
Which year was this Materials & Engineering question asked in UPSC Prelims?▼
This question was asked in UPSC CSE Prelims 1999, GS Paper 1, as Question 127. It falls under Science & Technology > Materials & Engineering.
What is the difficulty level of this UPSC question?▼
This question is rated "moderate". It requires sound conceptual understanding of the topic.
How many UPSC Prelims questions have been asked from Materials & Engineering?▼
UPSC has asked 23 questions from Materials & Engineering (under Science & Technology) across multiple years. Visit the topic page to see the full list and year-wise trends.