Write the reason for selecting the meth-ods for concentration of mercury and tin.

Froth flotation process, hydraulic washing, magnetic separation, leaching etc are some methods for concentration of ores? Which of this methods is useful for the separation of copper pyrites? b) Write the reason for choosing this method.

Write the expression showing the change of concentration with time in the exponential form for reactions of 1 st order?

Write down the reason for adding limestone along with the concentrated ore of iron.

Write the reason for the twinkling of stars in the sky.

Write the reason for the following: Action and reaction are equal and opposite.Yet they do not cancel each other.

Write suitable method of concentration for the ores given below

Write the reason for the following statements: Esters are used in perfumes and fruit juice.

Assertion :The rate of the reaction, A rarr B is the rate of change of concentration of a reactant or a product. Reason: Rate of reaction remains constant duringthe course of reaction.

Assertion :The order of a reaction maybe negative. Reason:In some cases, the rate of reaction decreases as the concentration of the reactant increases.