General Chemistry » Exercise - 19. Among the various allotropes of carbon : (a) coke is the hardest, graphite is the softest (b) diamond is the hardest, coke is the softest (c) diamond is the hardest, graphite is the softest (d) diamond is the hardest, lamp black is the softest
General Chemistry » Exercise - 14. Quartz crystals normally used in quartz clocks etc. is chemically : (a) silicon dioxide (b) germanium oxide (c) a mixture of germanium oxide and silicon dioxide (d) sodium silicate
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General Chemistry » Exercise - 114. Permanent hardness of water may be removed by the addition of : (a) sodium carbonate (b) alum (c) potassium permanganate (d) lime