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SOLUTION KEY TO PRACTICE EXAM II / CHAPTERS 4 & 5 / CHEM 1311 Part I. Multiple Choice (100 Points Total) # 01. (5 pts) To which category does the following reaction belong? PbSO 4 (aq) + K 2 O(s) PbO(s) + K 2 SO 4 (aq) a. a gas-forming reaction b. an acid-base reaction c. a precipitation reaction answer d. an oxidation-reduction reaction e. none of the above # 02. (5 pts) Determine the oxidation number of chromium in H 2 CrO 4 . You may want to may use of the oxidation number table on page 8. a. Cr + b. Cr 2+ c. Cr 3+ d. Cr 4+ e. Cr 6+ answer Solution: H = +1; O = -2; Cr = x 2(+1) + x + 4(-2) = 0 2 + x 8 = 0 x 6 = 0 x = 6 ( i.e. Cr 6+ ) # 03. (5 pts) Which one of the following is a weak acid? a. HCl b. HNO 3 c. H 2 SO 4 d. HBr e. Acetic acid (C 2 H 4 O 2 ) answer (all others are strong acids) # 04. (5 pts) Oxidation-reduction reactions always involve ____________ . a. the transfer of electrons b. an oxidizing agent c. a reducing agent d. a precipitate CHEM 1311/TAMUCC/J. M. Southard, PhD 1 e. a , b & c answer # 05. (5 pts) Balance the acid-base reaction with the smallest whole number coefficients . Ive placed blanks in front of each compound for your convenience. Choose the answer that is the sum of the coefficients in the balanced equation. Do not forget coefficients of one. 3 Ca(OH) 2 + 2 H 3 PO 4 (aq) 1 Ca 3 (PO 4 ) 2 (aq) + 6 H 2 O( l ) a. 4 b. 5 c. 8 d. 9 e. 12 answer (b/c 3 + 2 + 1 + 6 = 12) # 06. (5 pts) Based on the following balanced equation determine how many moles of O 2 are required to react with 23.5 moles of CH 3 OH? 2 CH 3 OH( l ) + 3 O 2 (g) 2 CO 2 (g) + 4 H 2 O(g) a. 47.0 b. 35.3 answer c. 11.8 d. 40.0 e. 23.5 Solution: 2 O mol 3 . 35 OH 3 CH mol 2 2 O mol 3 OH 3 CH mol 5 . 23 # 07. (5 pts) Based on the following balanced equation determine how many moles of H 2 can be produced from 72.9 g Mg and an excess of HCl. 2 HCl(g) + Mg(s) MgCl 2 (s) + H 2 (g) a. 4.50 mol b. 3.00 mol answer c. 1.50 mol d. 9.00 mol e. 6.00 mol Solution: 2 H mol 00 . 3 Mg mol 1 2 H mol 1 Mg g 31 . 24 Mg mol 1 Mg g 9 . 72 # 08. (5 pts) What is the identity of the oxidizing agent in the following oxidation-reduction reaction? 2 Mg(s) + S 2 (g) 2 MgS(s) a. Mg is reducing agent b/c Mg Mg 2+ ) CHEM 1311/TAMUCC/J. M. Southard, PhD 2 b. S 2 answer (is oxidizing agent b/c S S 2- ) c. MgS d. This reaction does not involve electron-transfer e. None of the above # 09. (5 pts) Based on the following balanced equation, what mass of SiF... View Full Document

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