List two advantages associated with water harvesting at the community level.

What steps would you suggest to minimise environmental pollution caused by burning of fossil fuels?

List the common food chain of a pond ecosystem

Explain the following

(a) The reactivity of a piece of aluminium metal decreases if it is dipped in HNO₃

(b) Carbon cannot reduce the oxides of Na or Mg

(c) NaCl does not conduct electricity in solid state whereas it does conduct electricity in aqueous solution as well as in molten state

(d) Necessity of galvanisation of iron articles

(e) Metals like Na, K, Ca and Mg are never found in their free state in nature.

OR

Given below are the steps for extraction of copper from its ore.

(a) Write the equations of the reactions involved in roasting of copper (I) sulphide followed by its reduction.

(b) Draw a neat labelled diagram for electrolytic refining

You are given the balls and sticks models of six carbon atoms and fourteen hydrogen atoms and sufficient number of sticks. In how many ways one can join the models of six carbon atoms and fourteen hydrogen atoms to form different molecules of C₆H₁₄.

OR

Draw structural formulae of all the possible isomers of the compound with molecular formula C₃H₆O and also give their electron dot structures.