a. Explain the formation of Calcium Chloride with the help of electron dot structure. (At numbers: Ca = 20; Cl = 17)

b. Why do ionic compounds not conduct electricity in solid state but conduct electricity in molten and aqueous state?

(a)Which of the following reactions is/ are an endothermic reaction(s) where decomposition also happens?

● Respiration

● Heating of lead nitrate

● Decomposition of organic matter

● Electrolysis of acidified water

b. Silver chloride when kept in the open turns grey. Illustrate this with a balanced chemical equation.

The following table shows the position of five elements A, B, C, D and E in the modern periodic table.

Answer the following giving reasons:

(i) Which element is a metal with valency two?

(ii) Which element is least reactive?

(iii) Out of D and E which element has a smaller atomic radius?

Refractive index of water with respect to air is 1.33 and that of diamond is 2.42.

(i) In which medium does the light move faster, water or diamond?

(ii) What is the refractive index of diamond with respect to water?

Match the following pH values 1, 7, 10, 13 to the solutions given below:

• Milk of magnesia

• Gastric juices

• Brine

• Aqueous Sodium hydroxide.

Amit and Rita decided to bake a cake and added baking soda to the cake batter

Explain with a balanced reaction, the role of the baking soda. Mention any other use of baking soda.

OR

(i) Four samples A, B, C and D change the colour of pH paper or solution to Green, Reddish-pink, Blue and Orange. Their pH was recorded as 7, 2, 10.5 & 6 respectively. Which of the samples has the highest amount of Hydrogen ion concentration? Arrange the four samples in the decreasing order of their pH.

(ii) Rahul found that the Plaster of Paris, which he stored in a container, has become very hard and lost its binding nature. What is the reason for this? Also, write a chemical equation to represent the reaction taking place.

(iii) Give any one use of Plaster of Paris other than for plastering or smoothening of walls.