Which polymer is used in making bulletproof glass? MCQ with Answer and Explanation

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Question #1

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The valency of aluminium in Al₂O₃ is:

A. 1

B. 4

C. 2

D. 3

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Correct Answer: Option D

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Explanation:
Aluminium oxide: Al³⁺ and O²⁻. To balance charges, 2 Al³⁺ (total +6) combine with 3 O²⁻ (total -6). Thus valency of Al is 3. It loses three electrons. Formula determined by criss-cross method.

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This question belongs to: Science chemistry

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Question #2

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Assertion (A): Silver and gold occur in the free state in nature. Reason (R): They are highly reactive metals.

A. A is false but R is true.

B. Both A and R are true but R is NOT the correct explanation of A.

C. A is true but R is false.

D. Both A and R are true and R is the correct explanation of A.

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Correct Answer: Option C

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Explanation:
Silver and gold are noble metals and occur in the free (native) state in nature because they are extremely unreactive (least reactive), not highly reactive. They do not readily combine with oxygen, moisture, or acids. Thus, A is true, but R is false.

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Question #3

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The temporary hardness of water is caused by the presence of:

A. Bicarbonates of calcium and magnesium

B. Chlorides of calcium and magnesium

C. Sulfates of calcium and magnesium

D. Nitrates of calcium and magnesium

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Correct Answer: Option A

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Explanation:
Water hardness is classified into temporary and permanent. Temporary hardness is caused by the dissolved bicarbonates of calcium and magnesium (Ca(HCO3)2 and Mg(HCO3)2). It is called 'temporary' because it can be easily removed by simple boiling, which decomposes the soluble bicarbonates into insoluble carbonates.

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