Why does a turmeric stain on white dress turn red when it is washed with soap?

Represent the following change in the form of equation:

Reaction between vinegar and baking soda

Represent the following change in the form of equation:

Reaction between ash obtained from burning of magnesium ribbon with water.
 

Represent the following change in the form of equation:

Reaction between an acid and a base.

Give reason for the following:

A shiny copper vessel turns green after some time.

Give reason for the following:

Iron pipes used in homes to carry water are galvanised.