QUIZ 1. Which reaction is considered a reduction reaction? a. 2Mg + O2 leads to 2MgO b. 2MgO + Carbon leads to 2Mg + CO2 c. 2Cu + O2 leads to 2CuO2 d. 2Al + Fe2O3 leads to Al2O3 + 2Fe Answer: b. Each of these is an oxidation reaction or a balanced redox reaction with the exception of the reaction in which MgO goes to magnesium solid, which is a true reduction reaction. 2. What is the best definition of an oxidation number? a. The number of electrons the atom is sharing with other atoms in a covalent bond b. The number of oxygen atoms attached to a compound c. The number of hydrogen atoms lost from a compound d. The imagined charge that an atom would have if it were a 100 percent ionic compound Answer: d. The oxidation number is the imagined charge on an atom if it were a 100 percent ionic compound. This makes it easier to determine whether something is oxidized or not. 3. What is the range of oxidation numbers for carbon as an atom in a reaction? a. 0 to +4 b. -4 to 0 c. 0 to +4 d. -4 to +4 Answer: d. The range of oxidation numbers for carbon is -4 for methane (a fully reduced carbon atom) to +4 for CO2, which is a fully oxidized carbon atom).
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