How would you test the presence of starch in leaves?

How would you detect the presence of sulphur in an organic compound by Lassaigne test.

Which gas is usually liberated when an acid reacts with a metal ? Illustrate with an example. How will you test for the presence of this gas ?

(i) Name the gas which is liberated when an acid reacts with a metal. How will you test the presence of the gas. (ii) Write the chemical equations for the reaction for zinc metal with : (a) Hydrogen acid and (b) Sodium hydroxide Write the chemical name of salt obtained in each case.

A student covered a leaf from a destarched plant with a black paper strip and kept it in a garden outside his house in fresh air, In the evening he tested the covered portion of the leaf for the presence of starch. By doing so the student was trying to show that:

How do you show the presence of following in glucose molecule : (i) Unbrached skeleton of six carbon atoms . (ii) Carbonyl group.