Aim How can we tell the difference between

Aim: How can we tell the difference between oxidizing and reducing agents? Do Now: 1. Take out a calculator and reference tables. 2. Write the oxidation states for each element in the following compounds: • HCl. O • Na. HCO 3 • Ag. NO 3 • Cl 2

Answer to do now HCl. O Na. HCO 3 Ag. NO 3 Cl 2

How can we tell if a reaction is a redox reaction? • Not all reactions are redox reactions. • To determine whether a redox reaction has occurred, assign oxidation numbers to each atom on the reactant and product sides. • If there is a change in oxidation numbers for any of the atoms, then a redox reaction has occurred. • Hint: If an uncombined element becomes part of a compound, it is a redox reaction. • Hint: Double replacement reactions are not redox.

Practice Problems Determine whether the following are redox reactions: Zn + HCl Zn. Cl 2 + H 2 Na. Cl + Ag. NO 3 Ag. Cl + Na. NO 3 Mn. O 2 + 4 HCl Mn. Cl 2 + 2 H 2 O

Another Problem • In the following reaction, which element is oxidized and which is reduced? 2 Fe 3+ + Sn 2+ 2 Fe 2+ + Sn 4+ • The Fe gains electrons and is thus reduced. • Because the Fe took its electrons from the Sn, it oxidized the Sn. • Because the Sn gave its electrons to the Fe, it reduced the Fe. • The element that is oxidized is said to be a reducing agent. • The element that is reduced is said to be an oxidizing agent.

Practice Problems In the following reactions, which are the oxidizing agents and which are the reducing agents? Explain. Co(s) +Pb. Cl 2(aq) Co. Cl 2(aq) + Pb(s) 2 Fe 3+ + Sn 2+ 2 Fe 2+ + Sn 4+