Laws of Chemical Combination PDF

Laws of Chemical Combination  Dalton’s Atomic Theory 1. Elements are made up of very small particles known as atoms. 2. All the atoms of an element are identical in mass and size, and are different from the atoms of another element. Dalton used the different shapes or figures to repres...

Laws of Chemical Combination  Dalton’s Atomic Theory 1. Elements are made up of very small particles known as atoms. 2. All the atoms of an element are identical in mass and size, and are different from the atoms of another element. Dalton used the different shapes or figures to represent different elements, as follows: 3.Compounds are composed of atoms of more than one element, combined in definite ratios with whole number values. 4. During a chemical reaction, atoms combine, separate, or rearrange. No atoms are created and no atoms disappear.  Introduction In the study of matter, we observe certain phenomena which can be reproduced at will. Scientific facts – observed phenomena that can be reproduced at will. Laws – a large number of scientific facts that can be summarized into broad or sweeping statements.  Laws of Chemical Combination 1. Law of Conservation of Mass 2. Law of Definite Proportion 3. Law of Multiple Proportions  Law of Conservation of Mass States that when an ordinary chemical reaction occurs, there is no detectable change in the masses of the substances involved before and after the reaction. masses of the reactants masses of the products before the reaction after the reaction Antoine Lavoisier A brilliant French chemist, formulated this law by describing one of his experiments involving mercuric oxide. He placed a small amount of mercuric oxide, a red solid, inside a retort and sealed the vessel tightly. He weighed the system, and then subjected it to high temperature. During the heating, the red solid turned into a silvery liquid. This observation indicated that a chemical reaction took place.After which, the setup was cooled and then weighed. The weight of the system was found to be the same as before heating. Sample Problem 5.19 g of CaCO3 when heated produced 1.99 g of Carbon dioxide and the residue (CaO) left behind weighs 3.2g. Show that these results illustrate the law of conservation of mass. Examples CaCO3 CaO + CO2 CH4 + 2O2 CO2 + 2H2O Na2CO3 + 2HCL 2NaCl + H2O + CO2  Law of Definite Proportion States that a given chemical compound always contain its component elements in fixed ratio (by weight) and does not depend on its source and method of preparation.  Law of Definite Proportion Given that 1.00 g hydrogen combines with 8.00 g oxygen. How many grams of hydrogen will react with 10.00 g oxygen? Solution Answer : 1.25 g  Law of Multiple Proportions States that when two elements combine to form more than one compound, the masses of one element which combine with a fixed mass of the other element are in a ratio of small whole numbers such as 2:1, 1:1, 2:3, etc. Sample Problem 1 In carbon monoxide, 1.00 g carbon combines with 1.33 g oxygen; whereas, in carbondioxide, 1.00 g carbon combines with 2.66 g oxygen. It can be seen that the ratio is 1:2. Summary a. Dalton differentiated the elements and their atoms through drawings. b. However, in present day, elements are differentiated and represented through symbols. i. Many symbols are abbreviations derived from the name of the element. ii. Some symbols are derived from their Latin names. Atoms, Molecules, Ions  Ions can be made up of only one atom (monoatomic) or more than one type of atom (polyatomic). Naming Monoatomic ions a. For cations, the name of the element is unchanged. b. If an element can form two ions of different charges, the name, which is usually derived from its Latin name, is modified by the suffix –ic for the ion with the higher charge, and – ous for that with the lower charge. b. For anions, the name of the element is modified by the suffix –ide. Naming Cations a. Zn2+ – zinc ion b. Mg2+ – magnesium ion c. K+ – potassium ion d. Fe2+ – ferrous ion or iron (II) ion e. Fe3+ – ferric ion or iron(III) ion Naming Anions a. Br- – bromide ion b. S2- – sulfide ion c. O2- – oxide ion d. I- – iodide  Polyatomic Ions Several anions are polyatomic and are named based on the atomic constituents and the suffix – ide. The most common examples are: a. OH- – hydroxide ion b. CN- – cyanide ion  A number of polyatomic anions containing oxygen atoms are named based on the root word of the central (or non-oxygen) atom and the suffix –ate for the one with more oxygen atoms and –ite for the one with less oxygen atom. a. NO3- nitrate ion b. NO2– nitrite ion c. SO32- – sulfite ion d. SO42- – sulfate ion e. PO43- – phosphate ion  Some anions have common names ending with the suffix –ate. a. C2H3O2- acetate ion b. C2O4 2- – oxalate ion Assignment: Research for the following Two types of chemical formulas Set of rules in naming Compounds and Acids Submission will be tomorrow, in short bondpaper, computerized. Write the references or website where you extracted the data.