Chem171Sp08Q5Key

Chem171Sp08Q5Key - 1. Chem 171 Quiz 5 Version A What is the...

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Chem 171 Quiz 5 Version A 1. What is the empirical formula of a compound that contains 29% Na, 41% S, and 30% O by mass? Na= 22.99, S=32.07, O=16.00 29g Na/22.99 g/mol = 1.26 mol Na 41g S /32.07g/mol = 1.28 mol S 30g O/ 16.00g/mol = 1.88 mol of O Na 1.26/1.26 S 1.28/1.26 O 1.88/1.26 Na 1.00 S 1.02 O 1.49 x 2 Na 2 S 2 O 3 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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Chem171Sp08Q5Key - 1. Chem 171 Quiz 5 Version A What is the...

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