Complete the following sentences by choosing the correct option from the brackets:

(a) The oxide that dissolves in caustic potash (KOH) is …………… . [ZnO / CuO]

(b) The reaction that takes place at the anode during the electrolysis of molten lead bromide is …………… . [2Br − 2e⁻ ⟶ 2Br⁻ / 2Br⁻ − 2e⁻ ⟶ Br₂]

(c) The volume occupied by 8 grams of oxygen gas at STP is …………… litres. [5.6 / 8.96] [Atomic weight of O = 16]

(d) …………… does not give hydrogen gas when it reacts with cold and very dilute nitric acid. [Cu / Mn]

(e) …………… is a polar covalent compound. [HCl / CCl₄]

Match Column A with Column B: Column A Column B (a) CuO + C ⟶ Cu + CO 1. Oxidation (b) Al3+ + 3e− ⟶ Al 2. Ionisation (c) PbBr2 ⟶ Pb2+ + 2Br1− 3. Reduction (d) 2O2− − 2e− ⟶ O2 4. Redox (e) HCl ⟶ H+ + Cl1− 5. Electrolytic dissociation

Identify the following terms / compounds: (a) A compound which reacts with water to give acetylene gas. (b) The gas evolved when sodium propanoate is heated with soda lime. (c) A reddish-brown precipitate formed when ferric chloride solution reacts with an alkali. (d) A pair of electrons present in an atom which is not shared with any other atom during bond formation. (e) The relative molecular mass of a substance expressed in grams.

Anil is a laboratory assistant in a college. He prepared nitric acid but stored it in a transparent container exposed to sunlight. After a few days, brown fumes were observed in the container and the acid turned slightly yellowish in colour. (a) What was the error made by Anil while storing the acid? (b) Why were brown fumes observed in the container? (c) How can the yellowish tinge in the acid be removed?

K, L and M are beakers containing three different solutions as shown below. Name the beaker which: (a) contains only ions. (b) contains only molecules. (c) has pH less than 7.

Study the reaction given below and answer the questions that follow: (a) Give one reason for maintaining the temperature below 200°C. (b) Why is concentrated Sulphuric acid used in the above reaction?

Zn + 4HNO3 ⟶ Zn(NO3)2 + 2H2O + 2NO2 32.5 g of zinc reacts with concentrated nitric acid as given in the above equation. (a) How many moles of zinc was required in the reaction? (b) Find the mass of nitric acid needed to react with 32.5 g of zinc. (c) Find the volume of nitrogen dioxide liberated in (b). [Atomic weight: H=1, N=14, O=16, Zn=65]

Equal volumes of ammonia gas and chlorine gas are kept in two different containers under the same conditions of temperature and pressure. Find the number of molecules contained in chlorine gas when the mass of ammonia is 34 g. [Atomic weight: Cl=35.5, H=1, N=14]

5.6 litres of gas Z weighs 32 g at STP. What is the molecular weight and vapour density of Z?

Differentiate between the following pairs based on the criteria given in the bracket: (a) Acetic acid and Sulphuric acid (number of replaceable hydrogen ion per molecule) (b) Electrolyte and Metallic conductor (the particles conducting electricity)

The diagram given below shows the electroplating of a spoon with silver. With reference to the diagram, answer the following questions: (a) Write an equation for the reaction that occurs at the cathode. (b) Silver nitrate solution is not preferred as an electrolyte in the above process. Give a reason. (c) Why is alternating current not used in the process? (d) What is the observation at the anode?

Carbon reacts with an acid to form carbon dioxide, water and nitrogen dioxide. (a) Name the acid used in the reaction. (b) Write a balanced chemical equation for the reaction that occurs.

Element A belongs to group 15 and period 2 of the Periodic Table. (a) Identify the element A. (b) Write the formula of the compound formed when element A combines with hydrogen. (c) Draw the dot (•) and cross (×) structure of the compound formed in (b) above.