BASIC LAWS OF CHEMISTRY

Standard of CompetenceUnderstanding the basic laws of chemistry and application in chemical calculation (stoichiometry)

Based of CompetenceProving and communicating the enactment of basic laws of chemistry through the experiment and apply the concept of the mole in chemical calculations.

Indicators1. Prove law of conservation mass by experiment2. Prove law of definite proportion by experiment 3. Analyzing compound to prove law of multiple

proportion.4. Using experimental data to prove the law of

combining volume 5. Using experimental data to prove Avogadro’s

hyphothesis

To make a cake need materials which have a proportion and certain amount. As make a cake, to produce compund also need constituent compounds or elements that have a certain amount and ratio.

Fundamental Law of

Chemistry

Law of Conservation

Mass (Lavoisier)

Law of Definite

proportion (Proust)

Law of Multiple

Proportion (Dalton) Law of

Combining Volume (Gay

Lussac)

Avogadro’s Hypotheisis

Law of Conservation Mass(Lavoisier’s Law)

Introduction

What is he said ?

Example

In close container, the total mass of substances present

after a chemical reaction is the same as the total mass of

substances before the reaction

Lavoisier’s Experiment

Mercury metal + Oxygen →Mercury calx530 g + 42,4 g 572,4 g

Example

24 g of copper and 12 g of sulfur react completely and form compound of copper sulfida. According to the law of conservation mass, how much copper sulfide can be obtain from the raction ?

Law of Definite Proportion(Proust’s Law)

What is he said ?

Example

Hydrogen and oxygen can form water with constant ratio

A chemical compund always contains the constant

proportion of elements by mass

Mass H2 (gram) Mass O2 (gram) Mass H2O (gram) Excess

1 1 8 9 -

2 2 16 18 -

3 1 9 9 1 gram O2

H : O = 1 : 8

Example

Ratio of sodium mass and chlorine mass that reacted are 1 : 8. What is the mass in gram of sodium chloride formed and what is the remaining element if 5 g of Na reacted with 16 g chlorine ?

Law of Multiple Proportion (Dalton’s Law)

What is he said ?

Example

Compound Mass of C (g) Mass of O (g)CO 6 9CO2 6 18

If there are two compounds formed from the same elements and if the mass of

one element in the two compound samples is same, the mass of the other

element is in the ratio of small whole number

Mass of O in CO 9 g 1= =

Mass of O in CO2 18 g 2

Example

Reaction of nitrogen and oxygen produced two compounds are nitrogen monoxide and nitrogen dioxide listed in tabel below.

Show that the ratio by mass of the nitrogen satisfies the Law of Multipe Proportion.

Compound

Mass of N(g)

Mass of O (g)

Mass of nitrogen monoxide

produced (g)

NO 9 3 5

NO2 18 3 21

Law of Combining VolumeGay-Lussac’s Law

What is he said ?

Example

2 H2(g) + O2(g) → 2 H2O(g)

2 volume 1 volume 2 volume

Ratio volume of H2 : O2 : H2O = 2 : 1 : 2

Ratio coeffisient of H2 : O2 : H2O = 2 : 1 : 2

At constant temperature and pressure. the volume of reacting

gases and volume of the producing gases is in the ratio of

small whole number

Volume A Coeffisient of A =

Volume B Coeffisient of B

Coeffisient of AVolume A = x volume B

Coeffisient of B

Example

5 L acetylene gas was burned completely by the reaction :

2C2H2(g) + 5O2(g) → 4CO2(g) + 2H2O(g)

At constant temperature and pressure, calculate :

a) volume of O2 gas required for reaction

b) volume of CO2 gas produced

Avogadro’s Hypothesis

What is he said ?

Example

At the same temperature and pressure, equal volume of

gases contain the same number of molecules

2 H2(g) + O2(g) → 2 H2O(l)

2 volume 1 volume 2 volume2 molecule 1 molecule 2 molecule

Ratio of molecule H2 : O2 : H2O = 2 : 1 : 2Ratio of volume of H2 : O2 : H2O = 2 : 1 : 2

Volume A Number of A gas molecule = Volume B Number of B gas molecule

Example

5 L of hydrocarbon gas CxHy reacts with 15 L of oxygen gas to form 10 L of carbon dioxide gas. Determine the chemical formula of the hydrocarbon gas.