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3123. Carbon refractories

do not burn/oxidise, when exposed to air on heating.
are not attacked by slags, as they are not wetted by melts.
do not resist temperature fluctuations.
have extremely low thermal & electrical conductivities.
✅ The correct answer is option B.

3085. Orsat apparatus is meant for

Gravimetric analysis of flue gas
Finding out combustion efficiency
Direct determination of nitrogen in flue gas by absorbing it in ammoniacal cuprous chloride
None of these
✅ The correct answer is option D.

3096. Naphthalene is used for making

Insecticides (e.g. moth balls)
Unsaturated polyesters
Drug intermediates e.g. β-naphthol
All of the above
✅ The correct answer is option D.

3068. Beehive coke oven

Facilitates by-products recovery
Takes 2-3 days for coking of coal but requires no external fuel for heating
Gives larger yield of coke (around 85%) as compared to by-product ovens
Produces coke with very poor strength
✅ The correct answer is option B.