Why does a block of plastic piece released under water come to the surface of water?

When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.00 g of carbon is burnt in 50.00 g of oxygen ? Which law of chemical combination will govern your answer?

What are polyatomic ions? Give examples.

(a) Magnesium chloride
(b) Calcium oxide
(c) Copper nitrate 
(d) Aluminium chloride
(e) Calcium carbonate

Give the names of the elements in the following compounds.

(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder 
(d) Potassium sulphate.

Calculate the molar mass of the following substances:

(a) Ethylene
(b) Sulphur molecule, S₈
(c) Phosphorus molecule, P₄
(d) Hydrochloric acid, HCl
(e) Nitric acid, HNO₃.

What is the mass of:

(a) 1 mole of nitrogen atoms

(b) 4 moles of aluminium atoms

(c) 10 moles of sodium sulphite.

Convert into mole

(a) 12 gm of oxygen gas

(b) 20 gm of water

(c) 22 gm of carbon dioxide.

What is the mass of?

(a) 0.2 mole oxygen atoms.

(b) 0.5 mole of water molecules.

Calculate the number of molecules of sulphur (S₈) present in 16 gm of solid sulphur.