Which of the following contains oxalic acid?

State the number of water molecules present in crystals of washing soda and Plaster of Paris. What are these water molecules called?

$A$ student prepared solutions of $(i)$ an acid and $(ii)$ a base in two separate beakers. She forgot to label the solutions and litmus paper is not available in the laboratory. Since both the solutions are colourless,how will she distinguish between the two?

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

Write balanced chemical equations for the following:
$(a)$ Calcium carbonate reacts with hydrochloric acid.
$(b)$ Calcium oxychloride reacts with hydrochloric acid.
$(c)$ Sodium hydroxide reacts with zinc.

What effect does an increase in the concentration of $H^{+}(aq)$ in a solution have on the $pH$ of the solution?