CHEMICAL REACTION AND EQUATIONS

Which of the following reaction is exothermic?

• QUICK LIME IN WATER TO PRODUCE SLAKED LIME

• CALCIUM CARBONATE IS HEATED TO PRODUCE CO2 + CaO

• LEAD NITRATE IS HEATED TO PRODUCE LEAD OXIDE, NITROGEN DIOXIDE AND O2

• MERCURIC OXIDE IS HEATED TO PRODUCE MERCURY AND OXYGEN

Lead nitrate solution is added to a test tube containing potassium iodide solution. Write the colour of the compound precipitated.

Which of the following is not a physical change?

• (a) Boiling of water to give water vapour

• (b) Melting of ice to give water

• (c) Dissolution of salt in water

• (d) Combustion of Liquefied Petroleum Gas (LPG)

The chemical reaction involved in the corrosion of iron metal is that of :

• (a) oxidation as well as displacement

• (b) reduction as well as combination

• (c) oxidation as well as combination

• (d) reduction as well as displacement

Why do we need to rub the magnesium ribbon with a sand paper before the activity ?