CHEMICAL REACTIONS Chapter 4 To play the movies and simulations included, view the presentation in Slide Show Mode. Reactants: Zn + I2 Product: Zn I2

4 Al(s) + 3 O2(g) ---> 2 Al2O3(s) Chemical Equations 4 Al(s) + 3 O2(g) ---> 2 Al2O3(s) This equation means 4 Al atoms + 3 O2 molecules ------> 2 formula units of Al2O3 4 moles of Al + 3 moles of O2 ----> 2 moles of Al2O3

Chemical Equations stoichiometric coefficients Depict the kind of reactants and products and their relative amounts in a reaction. 4 Al(s) + 3 O2(g) ---> 2 Al2O3(s) The numbers in the front are called stoichiometric coefficients The letters (s), (g), and (l) are the physical states of compounds.

It must have the same number of atoms of the same kind on both sides. Lavoisier, 1788 Chemical Equations Because of the principle of the conservation of matter, an equation must be balanced. It must have the same number of atoms of the same kind on both sides.

The Law of the Conservation of Matter Chemical Equations The Law of the Conservation of Matter The amount of matter in a system does not change: the same atoms are present in a reaction at the beginning and at the end.

Balancing Equations ___ Al(s) + ___ Br2(liq) ---> ___ Al2Br6(s)

Balancing Equations ____C3H8(g) + _____ O2(g) ----> _____CO2(g) + _____ H2O(g) ____B4H10(g) + _____ O2(g) ----> ___ B2O3(g) + _____ H2O(g)

STOICHIOMETRY - the study of the quantitative aspects of chemical reactions.

STOICHIOMETRY It rests on the principle of the conservation of matter. 2 Al(s) + 3 Br2(liq) ------> Al2Br6(s)

STOICHIOMETRY CALCULATIONS Stoichiometric factor Moles product Moles reactant

1. How many moles of acid are need to react all the zinc? Zn + HCl ð ZnCl2+ H2 2 Given 7 mol of Zn, 1. How many moles of acid are need to react all the zinc? 2. How many moles of hydrogen gas are produced? 3.How many moles of ZnCl2 are produced?

KClO3 ð KCl + O2 2 3 2 Given you need to produce 21 moles of oxygen gas: 1. How many moles of KClO3 do you need to start with? 2. How many moles of KCl are produced?

2 7 4 6 __C2H6+ O2 ð CO2+ H2O Given 10 moles of C2H6 : 1. How many mole of oxygen gas do you need to react all the ethane? 2. How many moles of water are produced? 3. How many moles of carbon dioxide will be produced?