State one relevant observation for the following reactions: Addition of excess ammonium hydroxide into copper sulphate solution.

When ammonium hydroxide is poured into the solution of blue coloured copper sulphate solution a blue coloured precipitate is formed. This precipitate is copper hydroxide that is insoluble in water. Ammonium sulphate is formed along with this. 2 NH 4 OH + CuSO 4 aq → Cu OH 2 s ↓ blue + NH 4 2 SO 4 When ammonium hydroxide is poured in excess it forms a complex deep blue solution of Cupra ammonium sulphate. 2 NH 4 OH + Cu OH 2 s blue + NH 4 2 SO 4 → Cu NH 3 4 SO 4 aq intense blue + 4 H 2 O

Write a balanced chemical equation for the following: The reaction of carbon powder and concentrated nitric acid.

Carbon gets oxidised when it reacts with concentrated nitric acid and liberates reddish-brown fumes of nitrogen dioxide. The balanced chemical reaction is as follows: C + 4 HNO 3 → CO 2 + 4 NO 2 + 2 H 2 O

State one relevant reason for the following: Hydrated copper sulphate crystals turn white on heating.

A molecule of hydrated copper sulphate crystals has five molecules of water of crystallization in it that maintains its crystal structure and gives it a blue colour. Upon heating these molecules evaporates leaving a white powder of copper sulphate behind.

State one relevant reason for the following: Concentrated nitric acid appears yellow when it is left for a while in a glass bottle.

Concentrated nitric acid is a colourless liquid but is thermally unstable. With a little heat the acid dissociates into reddish-brown nitrogen dioxide gas that dissolves in the acid and turns the acid yellow.

Differentiate between the following pair based on the information given in the bracket. Acid and Alkali (formation of the type of ions)

An Acid is a sour-tasting substance that dissociates in water to give hydrogen ions whereas an alkali is a water-soluble base that dissociates in water to give hydroxyl ions.

Write a balanced equation for the preparation of the following salt: Zinc carbonate from Zinc sulphate.

When zinc sulphate reacts the sodium carbonate, sodium sulphate and zinc carbonate are formed. In this reaction, exchange of ions of both the substances takes place. The reaction involved in the formation of zinc carbonate from zinc sulphate is given as; ZnSO 4 aq + Na 2 CO 3 aq → Na 2 SO 4 aq + ZnCO 3 s

Write a balanced equation for the preparation of the following salt: Copper sulphate from Copper carbonate.

Acid on reacting with metal carbonates liberate a colourless, odourless gas with brisk effervescence which turns lime water milky. CuCO 3 s + H 2 SO 4 aq → CuSO 4 s + CO 2 g + H 2 O l

Give a chemical test to distinguish between the following pair of chemicals: Sodium chloride solution and Sodium nitrate solution.

Silver nitrate will react with sodium chloride to form white precipitate of silver chloride. On the other hand, sodium nitrate will not react with silver nitrate. NaCl ( aq ) + AgNO 3 aq → AgCl ↓ + NaNO 3 aq NaNO 3 aq + AgNO 3 aq → No reaction

Three solutions P , Q and R have pH value of 3.5 , 5.2 and 12 . 2 respectively. Which one of these is a weak acid?

Acids have pH less than 7 . The strength of an acid depends upon number of H + ions produced by a substance. Weak acids do not dissociate completely in water. Thus, the concentration of H + ions is relatively less hence they will have more pH value and less than 7 . Therefore, the solution Q is a weak acid.

Three solutions P , Q and R have pH value of 3.5 , 5.2 and 12 . 2 respectively. Which one of these is a strong alkali?

The solution whose pH is greater than 7 , is a basic solution or alkaline solution. The more basic solution is, the higher will be its pH. Thus, R with pH value 12 . 2 is a strong alkali.

Complete the following table which refers to the conversion of ions to neutral particles. Conversion Ionic equation Oxidation/Reduction Chloride ion to chlorine molecule Lead II ion to lead

Conversion Ionic equation Oxidation/Reduction Chloride ion to chlorine molecule 2 Cl - - 2 e - → Cl 2 Oxidation Lead II ion to lead Pb 2 + + 2 e - → Pb Reduction The removal of electrons from substance is known as oxidation. When an electron is removed from the chloride ion Cl - , a chlorine atom is formed. Two chlorine atoms combine to a chlorine molecule. The addition of electrons to a substance is known as reduction. When two electrons are added to the lead ion Pb 2 + , the 2 + charge gets neutralised to form lead Pb atom.

Name the gas that is produced in the following case: Action of dilute hydrochloric acid on sodium sulphide.

Sodium sulphide decomposes into sodium chloride with the release of hydrogen sulphide gas on reacting with dilute hydrochloric acid. The chemical reaction can be written as: Na 2 S aq + 2 HCl aq → 2 NaCl aq + H 2 S g

State one relevant observation for of the following: Barium chloride solution is slowly added to sodium sulphate solution.

When barium chloride solution is slowly added to sodium sulphate solution, a white precipitate of barium sulphate is formed along with sodium chloride. BaCl 2 aq + Na 2 SO 4 aq → BaSO 4 s + 2 NaCl aq