Figure 1
Introduction Redox reactions involve the transfer of electrons between atoms. The compound that loses an electron is said to be oxidized, the one that gains an electron is said to be reduced. A compound that is oxidized is referred to as a reducing agent, while a compound that is reduced is referred to as an oxidizing agent. The oxidation number is a number identical with the valence or number of bonds that an atom can form but with the addition of a + sign to indicate missing electrons or a – to indicate additional electrons. Thus, the oxidation number of chlorine in hydrochloric acid is -1, while it is +1 in hypochlorous acid. Similarly we can say that the oxidation number of chlorine in chloric acid (HCIO3) is +5, and in perchloric acid (HCIO4) +7. In this experiment we will be following the temperature changes that occur during redox reaction: (1)
0 0 − 3+ − 3Cu2+ (aq) + 6Cl(aq) + 2Al(s) → 3Cu(s) + 2Al(aq) + 6Cl(aq)
Aluminum, Al, was oxidized to Al3+, Cu2+ was reduced to Cu. The heat of reaction can be calculated from the following equation: q = Ct (2)