Organic Chemistry — Chemistry STD 10 — Question

Calculate the empirical formula of a compound having the following percentage composition.
[Na = 42.1%, P = 18.9% and oxygen = 39%]
[Na = 23, P = 31 and O = 16].

Write balanced chemical equations for the following :
(a) Chlorine reacts with excess of ammonia.
(b) Ferric hydroxide reacts with nitric acid.
(c) Zinc oxide dissolves in sodium hydroxide.

The following questions are relevant to the extraction of Aluminium :
(i) State the reason for addition of caustic alkali to bauxite ore during purification of bauxite.
(ii) Give a balanced chemical equation for the above reaction.
(iii) Along with cryolite and alumina, another substance is added to the electrolyte mixture. Name the substance and give one reason for the addition.

In a chemistry lab, a student is given a solution containing an unknown cation. The student adds sodium hydroxide (NaOH) to the solution and observes the formation of a blue precipitate. The student then decides to add ammonium hydroxide to a fresh sample of the solution in excess.
(a) Identify the cation.
(b) What happens when excess of NaOH is added in the solution?
(c) What happens when excess of ammonium hydroxide is added to the solution?

(a) What are the terms defined by the following?
(i) A salt containing a metal ion surrounded by other ions or molecules.
(ii) A base which is soluble in water.
(b) Making use only of substances chosen from those given below:
Dilute sulphuric acidSodium Carbonate
Zinc Sodium sulphite
Lead Calcium carbonate
Give equations for the reactions by which you could obtain :
(i) Hydrogen
(ii) Sulphur dioxide
(iii) Carbon dioxide
(iv) Zinc carbonate (two steps required)

State your observation when the following are exposed to the atmosphere.
(a) Washing soda crystals
(b) Iron (III) chloride salts

Explain the following : Catenation