Calcium oxide reacts vigorously with water to produce:

Solid calcium oxide reacts vigorously with water to form calcium hydroxide accompanied by liberation of heat. This process is called slaking of lime. Calcium hydroxide dissolves in water to form its solution called lime water. Which among the following is (are) true about slaking of lime and the solution formed?
$(i)$ It is an endothermic reaction
$(ii)$ It is an exothermic reaction
$(iii)$ The $pH$ of the resulting solution will be more than seven
$(iv)$ The $pH$ of the resulting solution will be less than seven

State one basic difference between a physical change and a chemical change.

Translate the following statements into chemical equations and then balance them.
$(a)$ Hydrogen gas combines with nitrogen to form ammonia.
$(b)$ Hydrogen sulphide gas burns in air to give water and sulphur dioxide.

State the reason for the following:
$(a)$ Potato chips manufacturers usually flush bags of chips with nitrogen gas.
$(b)$ Iron articles lose their shine gradually.
$(c)$ Foods should be kept in airtight containers.

In the double displacement reaction between aqueous potassium iodide and aqueous lead nitrate,a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate is not available,which of the following can be used in place of lead nitrate?