8th Class Science Sample Paper Science Sample Paper-9

  • question_answer
    Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.                                 
    (i) How will she find the nature of the gas?
    (ii) Write down word equations of all reactions taking place in this process.

    Answer:

    (i) When charcoal is burnt, carbon dioxide gas is produced. This gas turns lime water milky. The nature of the gas can be tested by using moist red and blue litmus paper. No effect on red litmus but the gas turns blue litmus to red, so it is acidic in nature.                                                       
    (ii) Equations of all the reactions are:
    \[\begin{align}   & \,\,\,\,\,\,\,C\,\,\,\,\,\,+\,\,\,\,\,\,\,\,\,{{O}_{2}}\,\,\,\,\,\,\to \,\,\,C{{O}_{2}} \\  & \operatorname{Carbon}\,\,\,\,\,Oxygen\,\,\,\,\,\,\,Carbon\,dioxide \\ \end{align}\]
    \[\operatorname{Carbon}\,dixide\,\,+\,\,Lime\,water\,\,\to \,\,Milky\]
    \[\begin{align}   & \operatorname{Carbon}\,dixide\,\,+\,\,\operatorname{Blue}\,Litmus\,\,\to \,\,\operatorname{Red} \\  & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(moist) \\ \end{align}\]


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