15. Which substance is conned when silica is melted (so that SiO4 units arc reor

Question

15. Which substance is conned when silica is melted (so that SiO4 units arc reorganized) and then cooled? a. clay b. glass c. talc d. feldspar 16. Older glass Coke bottles were green due to the presence of this metal ion in the silica from which the bottle was made. a. Fe^+2 b. Cu^+ c. Sn^+4 d. Ca^+2 17. Pyrex and Kimax glass typically contain an oxide of this element which gives the glass a small coefficient of thermal expansion. a. sodium b. lead c. boron d. arsenic 18. Which does not apply to silicates? a. clay b. tetrahedral units c. contains carbon d. SiO2

Explanation / Answer

15. Which substance is formed when silica is melted(so that SiO4 units are reorganized) and then cooled?
a. clay
b. glass
c. talc
d. feldspar

Answer: (b). glass is formed when silica is melted(so that SiO4 units are reorganized) and then cooled?

16. Older glass Coke bottles were green due to the presence of this metal ion in the silica from which the bottle was
made.
a Fe+2
b. Cu+
c. Sn+4
d. Ca+2

Answer: (a) FeO and Cr2O3 are used for the production of green bottles.

17. Pyrex and Kimax glas typically contain an oxide of this element which give the glass a small coefficient of thermal expansion
a. sodium
b. lead
c. boron
d. arsenic

Answer: (c) Boron oxide is added to h give the glass a small coefficient of thermal expansion. The lower the coefficient of expansion the more resistant the glass is to thermal shock.

18. Which does not apply to silicates?
a. clay
b. tetrahedral units
c. contains carbon
d. SiO2

Answer. (c) silicates don't contain carbon. Silicates SiO4 has tetrahedron structure. Silicates when regular produce crystalline quartz SiO2. Silicates are also found in micas and clays.

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