Chemical Compounds and Reactions

Elements and Compounds Atom : the smallest unit of an element that can exist alone or in combination with other elements. Atom : the smallest unit of an element that can exist alone or in combination with other elements. Molecule: the smallest particle of a compound or gaseous element that can exist and still retain the characteristic chemical properties of a substance Molecule: the smallest particle of a compound or gaseous element that can exist and still retain the characteristic chemical properties of a substance

Making Molecules Chemical Bond: an attractive force that holds atoms together in a compound Ionic: when atoms transfer electrons to achieve a noble gas electron arrangement. Ionic: when atoms transfer electrons to achieve a noble gas electron arrangement. Covalent: when atoms share electrons to achieve a noble gas electron arrangement Metallic: formed in solid metals

Definitions Chemical Compound: a substance resulting from chemical bonding of two or more elements. Chemical Compound: a substance resulting from chemical bonding of two or more elements. Chemical Formula: a symbolic identification of the elements making up a compound. Chemical Formula: a symbolic identification of the elements making up a compound. Chemical Reaction: a process of interacting elements or compounds to form other elements or compounds. Chemical Reaction: a process of interacting elements or compounds to form other elements or compounds.

Balancing Reactions In a reaction: Atoms are neither lost nor gained Atoms are neither lost nor gained Formula subscripts cannot be changed. Formula subscripts cannot be changed. Formula coefficients multiply all elements (including subscripts) in the formula Formula coefficients multiply all elements (including subscripts) in the formula

Chemical Reactions Combination - two or more substances combine to form a single compound Combination - two or more substances combine to form a single compound 4 Fe(s) + 3 O 2 (g) = 2 Fe 2 O 3 (s) 4 Fe(s) + 3 O 2 (g) = 2 Fe 2 O 3 (s) Decomposition - a compound is broken into smaller elements of compounds Decomposition - a compound is broken into smaller elements of compounds 2 HgO(s) = 2 Hg(s) + O 2 2 HgO(s) = 2 Hg(s) + O 2 Replacement - atoms of one reactant are exchanged by atoms of other reactants Replacement - atoms of one reactant are exchanged by atoms of other reactants 2 Al(s) + 3 CuCl 2 (Aq) = 2 AlCl 3 (Aq) + 3 Cu(s) 2 Al(s) + 3 CuCl 2 (Aq) = 2 AlCl 3 (Aq) + 3 Cu(s) Ion Exchange - ions of reactants interact to form a solid, a gas, or water Ion Exchange - ions of reactants interact to form a solid, a gas, or water 3 Ca(OH) 2 + Al 2 (SO 4 ) 3 = 3 CaSO Al(OH) 3 3 Ca(OH) 2 + Al 2 (SO 4 ) 3 = 3 CaSO Al(OH) 3

Balancing Equations 1) Ca(OH) 2 + Al 2 (SO 4 ) 3 = CaSO 4 + Al(OH) 3 1) Ca(OH) 2 + Al 2 (SO 4 ) 3 = CaSO 4 + Al(OH) 3 2) Ca(OH) 2 + Al 2 (SO 4 ) 3 = CaSO 4 + Al(OH) 3 2) Ca(OH) 2 + Al 2 (SO 4 ) 3 = CaSO 4 + Al(OH) 3 3) Ca(OH) 2 + Al 2 (SO 4 ) 3 = CaSO 4 + Al(OH) 3 3) Ca(OH) 2 + Al 2 (SO 4 ) 3 = CaSO 4 + Al(OH) 3 4) 3Ca(OH) 2 + Al 2 (SO 4 ) 3 = 3CaSO 4 + 2Al(OH) 3 4) 3Ca(OH) 2 + Al 2 (SO 4 ) 3 = 3CaSO 4 + 2Al(OH) 3 5) 3Ca(OH) 2 + Al 2 (SO 4 ) 3 = 3CaSO 4 + 2Al(OH) 3 5) 3Ca(OH) 2 + Al 2 (SO 4 ) 3 = 3CaSO 4 + 2Al(OH) 3

Quantitative Measures A formula gives the mass ratio of elements in a compound A formula gives the mass ratio of elements in a compound A formula mass is the sum of the atomic masses of its elements A formula mass is the sum of the atomic masses of its elements The total mass of reactants in a chemical reaction must equal the total mass of products. The total mass of reactants in a chemical reaction must equal the total mass of products. Mass units may be in any consistent system of units (g, kg, lb, tons, etc.) Mass units may be in any consistent system of units (g, kg, lb, tons, etc.)