Task 1.2a Working out formulae from reacting masses

1. What is the empirical formula of a compound containing 4.6g Na, 2.8g N, 9.6g O.

2. Find the empirical formula of a compound containing 85.7% C, and 14.3% H by mass.

3. 1.24g of phosphorus was burnt completely in oxygen to give 2.84g of phosphorus oxide.  Find (a) the empirical formula of the oxide, and (b) the molecular formula of the oxide, given that the molar mass of the oxide is 284gmol^-1.

4. An organic compound 66.7% C, 11.1% H and 22.2% O by mass.  Its relative formula mass was 72.  Find (a) the empirical formula of the compound of the compound and (b) the molecular formula.

5  Work out the empirical formulae of compounds made from the following:
(a) 12g carbon and 4g of hydrogen
(b) 414g lead and 32 g of oxygen
(c) 1.2g of carbon and 3.2 g of oxygen
(d) 11.2 g of iron and 4.8g of oxygen
(e) 3.2g of copper, 0.6g of carbon and 2.4g of oxygen.

6. An oxide of copper in a dish was reduced in a stream of hydrogen.  The results were;
mass of dish = 25.00g
mass of oxide of copper + dish (before reaction) = 29.0g
mass of copper left + dish (after reaction) = 28.2g
Work out the empirical formula of the oxide.