Answers to questions on "Chemical formulae and chemical equations" post

Answers to questions on a previous post, titled "Chemical formulae and chemical equations" 

1. Magnesium + hydrochloric acid à Magnesium chloride + hydrogen
2. Mg + HCl à MgCl₂+ H₂
3. Zinc + hydrochloric acid à zinc chloride + hydrogen
4. Zn + HCl à ZnCl₂ + H₂
5. Magnesium + nitric acid à Magnesium nitrate + hydrogen
6. Mg + 2HNO₃ à Mg(NO₃)₂ + H₂
7. Zinc + sulphuric acid à zinc sulphate + hydrogen
8. Zn + H₂SO₄ à ZnSO₄ + H₂
9. Iron + hydrochloric acid à iron chloride + hydrogen
10. Fe + 2HCl à FeCl₂ + H₂

Sodium + water à sodium hydroxide + hydrogen

Magnesium + water à magnesium hydroxide + hydrogen

Magnesium + steam à magnesium oxide + hydrogen

Iron + steam à iron oxide + hydrogen

2 Na + 2 H₂O à 2 NaOH +  H₂

Mg + H₂O_(g) à MgO + H₂

Mg + 2 H₂O_(l) à Mg(OH)₂ + H₂

Formula	Name
CO2	Carbon dioxide
SO2	Sulphur dioxide
SO3	Sulphite/sulphur trioxide
HCl	Hydrogen chloride (only hydrochloric acid if aqueous)
H2S	Hydrogen sulphide
Li3N	Lithium nitride
NaCl	Sodium chloride
NaNO3	Sodium nitrate
Na2CO3	Sodium carbonate
Cu(NO3)2	Copper nitrate
FeCl2	Iron chloride
Fe(OH)3	Iron (III) hydroxide
BaCl2	Barium chloride
Fe2(SO4)3	Iron sulphate
ZnCl2	Zinc chloride
AlCl3	Aluminium chloride
Ca(NO3)2	Calcium nitrate
PbO	Lead (II) oxide
PbO2	Lead dioxide
Ca(OH)2	Calcium hydroxide
CaCl2	Calcium chloride
ZnSO4	Zinc sulphate
AgNO3	Silver nitrate
NaHCO3	Sodium bicarbonate
(NH4)2SO4	Ammonium sulphate
KAt	Potassium astatide
NH4Cl	Ammonium chloride

Work out the empirical formulae for the following compounds:

1. Ca (40%), C (12%), O (48%)

EF= CaCO₃

2. Na (32.4%), S (22.5%), O (45.1%0

EF= Na₂SO₄

3.  Pb (92.8%), O(7.2%)

EF= PbO

4.  Pb (90.66%), O(9.34%)

EF= Pb₃O₄

5.  C (75%), H (25%)

EF= CH₄

Work out the molecular formula of these compounds:

1.       C (40%), H (6.67%), O (53.3%), M_r=60

EF= CH₂O    MF=C₂H₄O₂

2.       H-0.5g, S-16g, O-32g, M_r=194

EF=HSO₄      MF= H₂S₂O₈