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s11q5Key - 1 Chem 171 Quiz 5 Version A A student performing...

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Chem 171 Quiz 5 Version A 1. A student performing the experiment entitled “Empirical Formula of Copper Chloride, did not wait before weighing the copper. Briefly explain how this will affect the determination of the empirical formula. The copper may still be wet Making it too heavy 2. Does zinc dissolve in hydrobromic acid? If so, write relevant molecular, complete ionic and net ionic equations; show the states. Identify any reducing agent and/or oxidizing agents if present. Yes Zn(s) + 2HBr(aq) ZnBr 2 (aq) + H 2 (g) Zn(s) + 2H + (aq) + 2Br - (aq) Zn 2+ (aq) + 2Br - (aq) + H 2 (g) Zn(s) + 2H + (aq) Zn 2+ (aq) + H 2 (g) Zn is the reducing agent; HBr (H + ) is the oxidizing agent Chem 171 Quiz 5 Version B 1. A compound is composed of C,H,O. The combustion of a 0.519 g sample of the compound yields 1.24 g CO 2 and 0.255 g of H 2 O. What is the empirical formula of the compound? C = 12.01, O= 16.00, H=1.01 1.24 g CO 2 / 44.01 g/mol x 1mol C/mol CO 2 = 0.0282 mol C 0.255 g H 2 O/18.02 g/mol x 2 mol H/mol H 2 O = 0.0283 mol H g of C = 0.0282 mol C x 12.01 g/mol =0.339 g and g of H = 0.0283 mol H x 1.01 g/mol = 0.0286 g g of O = 0.519 g – (0.339+0.0286) = 0.151 g
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