Laws Of Chemical Combination

CONTENT

• Law of conservation of mass
• Law of definite proportion or constant composition
• Law of multiple proportion

LAW OF CONSERVATION MASS

This law states that during chemical reactions, matter can neither be created nor destroyed but changes from one form to another.

LAW OF DEFINITE PROPORTION OR CONSTANT COMPOSITION

The law states that all pure samples of a particular chemical compound contain the same elements combined in the same proportion by mass.

LAW OF MULTIPLE PROPORTIONS

This states that if two elements combine to form more than one compound, the masses of one of the elements which separately combine with fixed mass of the other element are in simple ratio

GENERAL EVALUATION/REVISION

1. State the law of (a) definite proportion (b) multiple proportion
2. Balance the following chemical equation
3. Ca(HCO₃)_2(s) → CaCO_3(s) + H₂O_(l) + CO_2(g)
4. SO_2(g) + H₂O_(l) + 0_2(g) → H₂SO_4(aq)
5. Determine the oxidation number of: (a) Cu in CuCO₃ (b) P in H₃PO₄ and name the compound

READING ASSIGNMENT

New School Chemistry for Senior Secondary School by O.Y.Ababio, Pg 34-37

WEEKEND ASSIGNMENT

1. All pure samples of chemical compound contain the same element in the same proportion    by mass is a the law of—— A. definite proportion B. reciprocal proportion C. multiple    proportion

D. conservation of matter

• What is used to measure the mass of atom and molecules? A. Beam balance B. Spring balance   

C. Chemical balance   D. Mass spectrometer

• What is the ratio by mass of oxygen and hydrogen in 1 mole of water?A. 3:1 B. 2:1 C.1:2 D. 2:4
• In two separate experiments 0.18g and 0.36g of chlorine combine with a metal M, to give A and B respectively. An analysis showed that A and B contain 0.10g and 0.20g of M     respectively. Which law is illustrated by the data? A A. Law of multiple proportions.  B.Law of conservation of mass.

C. Law of constant composition.  D. Law of simple proportion

• An element E forms the following compounds with bromine: EBr₂, EBr₃, and EBr4. This observation illustrates the A. Law of conservation of mass.B. Law of definite    proportion.C. Law of multiple proportion.D. Law of chemical combination

THEORY

1. 8.50g of CuO when heated in a current of dry hydrogen gas gave 6.58g of copper and 2.16g of water. Calculate the proportion of oxygen to hydrogen by mass in water.
2. Balance the following equations:

       C₄H₁₀ + O₂  → CO₂ + H₂O

       H₂SO₄ + NaOH → Na₂SO₄ + H₂O