A is a compound of calcium. On heating A a colourless gas B and a resides C are formed. When C is dissolved in water a compound D is obtained. When excess `CO_2` is passed through the aqueous solution of D, E is formed. E on gentle heating gives A. Identify A, B, C and E.

On passing CO_2 through clear lime water, it turns milky. What happens when more C O_2 is passed to the milky solution? Why?

Element A burns, in nitrogen to give an ionic compound B. The compound B reacts with 'H2O' to give 'C' and 'D'. A solution of 'C' becomes milky on bubbling 'CO2'. Identify 'A, B, C, D'.

When a white crystalline compound 'X' is heated with K_(2)Cr_(2)O_(7) and concentrated H_(2)SO_(4) a red dish brown gas 'A' is evolved. On passing 'A' into caustic soda solution, a yellow coloured solution of 'B' is obtained. Neutralising the solution 'B' with acetic acid and on subsequent addition of lead acetate a yellow precipitate C is obtained. When 'X' is heated with NaOH a colourless gas is evolved and on passing this a gas into K_(2)HgI_(4) (Nessler's reagent) solution a reddish brown precipitate D is formed. Identify '(A), (B), (C), (D) and X. Write equations for the reactions involved.

What is the coordination entity formed when excess of aquéous KCN , iș added to an aqueous solution of copper sulphate? Why is it that no precipitate of copper sulphide is obtained when H_2 S(g) is passed through this solution?

An organic compound A, C₈H₆ on treatment with dilute sulphuric acid-containing mercuric sulphate gives a compound B , which can also be obtained from a reaction of benzene with an acid chloride in the presence of anhydrous aluminium chloride. The compound B, when treated with Iodine in aqueous KOH, yields C and a yellow compound D. Identify A B C and D with justification.

Compound A is treated with ethanolic NaCN to give the compound C_2H_5CN (B) compound B on reduction gives compound C. identify compounds A and C.

By passing chlorine gas through a colourless solụtion, we get bleaching powder. (a) What happens if CO_2 is passed instead of Cl_2 ? (b) When CO_2 is passed in excess, what changes can you observe?

When metal 'X' is treated with sodium hydroxide, a white precipitate (A) is obtained, which is soluble in excess of NaOH to give soluble complex (B). Compound (A) is soluble in dilute HCl to form compound (C). The compound (A) when heated strongly gives (D), which is used to extract metal. Identify ( 'X' ), (A), (B), (C) and (D). Write, suitable equations to support their identities.