August 2018 NY Regents Chemistry Exam
46 Given the equation representing a reaction: Cd+NiO2+2H2O→Cd(OH)2 + Ni(OH)2 Which half-reaction equation represents the oxidation in the reaction?
Solution: We can remember the mnemonic OIL RIG. OIL (oxidation is loss of electrons). RIG (reduction is gain of electrons). For this question, we are looking for an oxidation half reaction. Oxidation means electrons are lost and we should see them on the right side of the equation, eliminating choices 1 and 4. Furthermore, the charge on both sides of the equation needs to be the same. For choice 2 the charge on the left is 4+ and on the right is 0 (+2-2=0). This eliminates choice 2. In choice 3, the charge on the left is 0 and the charge on the right is 0 (+2-2=0).
Answer: 3
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