What is the effect of an acid on litmus paper?

In the following schematic diagram for the preparation of hydrogen gas as shown in the Figure,what would happen if the following changes are made?
$(a)$ In place of zinc granules,the same amount of zinc dust is taken in the test tube.
$(b)$ Instead of dilute sulphuric acid,dilute hydrochloric acid is taken.
$(c)$ In place of zinc,copper turnings are taken.
$(d)$ Sodium hydroxide is taken in place of dilute sulphuric acid and the tube is heated.

Differentiate between strong electrolytes and weak electrolytes. Mention two examples each.

Sodium carbonate is a basic salt because it is a salt of

Which gas is released when acid reacts with metal carbonate or metal hydrogen carbonate?

What are antacids? Explain their role in providing relief from stomach ache.