Balancing Equations Unit 5 Lesson 1 Demos It is Eggothermic

Chemical Reactions A chemical reaction is a process in which physical and chemical properties of the original substance change as existing bonds are broken and new bonds are formed giving new substances with different physical and chemical properties.

Evidence of Chemical Rxns Temperature Change Energy released or absorbed (heat, light) Color change Gas formation Appearance of a solid (precipitate) Formation of water

Reactants and Products Reactants are the substances you consume in a reaction Products are the substances that you produce in a reaction HCl + NaOH  H2O + NaCl Reactants Products

calcium + oxygen  calcium oxide Chemical Equations Word Equations calcium + oxygen  calcium oxide Formula (skeleton) Equations Ca + O2  CaO

Balancing Equations 3Mg + N2  Mg3N2 Law of Conservation of Matter indicates that the number of atoms of each type of element must be the same in the reactants and the products A coefficient is the number placed in front so that reactants equal products Coefficients may only be placed in front of the molecules/elements (you cannot change subscripts) Subscripts need to be determined before the equation can be balanced Reactants must equal products. The Law of Conservation of Matter must be fulfilled. 3Mg + N2  Mg3N2

Steps for Balancing Products Reactants 1 C 1 C 2 H 4 H 3 O 2 O 1. Write the equation. CH4 + O2  CO2 + H2O 2. Do an atom inventory. Products 1 C 2 H 3 O Reactants 1 C 4 H 2 O

Reactants 1 C 4 H 4 O Products 1 C 4 H 4 O 3. Add coefficients to make the equation balance. CH4 + ___O2  CO2 + ___H2O 4. Check your answer. 2 2 Reactants 1 C 4 H 4 O Products 1 C 4 H 4 O Balance oxygen last and hydrogen second to last.

Sample Problem 1 ____Al + ___O2  ___Al2O3 4Al + 3O2  2Al2O3 Write a balanced chemical equation for the reaction in which aluminum reacts with oxygen to produce aluminum oxide. ____Al + ___O2  ___Al2O3 4Al + 3O2  2Al2O3

Sample Problem 2 2HCl + CaCO3  CaCl2 + H2O + CO2 Write a balanced chemical equation for the reaction in which hydrochloric acid reacts with calcium carbonate to produce calcium chloride, water, and carbon dioxide. _HCl + _CaCO3  _CaCl2 + _H2O + _CO2 2HCl + CaCO3  CaCl2 + H2O + CO2

Samples __BeF2 + __ Al2O3  __ BeO+ __ AlF3 __PbO + __HCl  __H2O + __PbCl2