The formula of soda ash is

A substance which gives brick red flame and breaks down on heating to give oxygen and a brown gas is

Which of the following statements is true about $\mathrm{Ca}(\mathrm{OH})_2$ ?

A chemical $A$ is used for the preparation of washing soda to recover ammonia. When $\mathrm{CO}_2$ is bubbled through an aqueous solution of A , the solution turns milky. It is used in white washing due to disinfectant nature. What is the chemical formula of $A$ ?

Dehydration of hydrates of halides of calcium, barium and strontium i.e., $\mathrm{CaCl}_2 \cdot 6 \mathrm{H}_2 \mathrm{O}, \mathrm{BaCl}_2 \cdot 2 \mathrm{H}_2 \mathrm{O}, \mathrm{SrCl}_2 \cdot 2 \mathrm{H}_2 \mathrm{O}$, can be achieved by heating. These become wet on keeping in air. Which of the following statements is correct about these halides?