/6 Science Quiz (for 12 to 16 years old): Quiz 18 1 / 6Permanent hardness of water may be removed by the addition of sodium carbonate alum lime potassium permanganate 2 / 6The hardest substance available on earth is Diamond Iron Platinum Gold 3 / 6Soda water contains nitrous acid carbonic acid carbon dioxide sulphuric acid 4 / 6Bromine is a highly inflammable gas black solid colourless gas red liquid 5 / 6Potassium nitrate is used in salt glass fertiliser medicine 6 / 6Which of the gas is not known as greenhouse gas? Methane Carbon dioxide Nitrous oxide Hydrogen Your score is 0% Restart quiz Next quiz Please rate the quiz Send feedback By WordPress Quiz plugin