04_Petrucci10e_SSM

04_Petrucci10e_SSM - CHAPTER 4 CHEMICAL REACTIONS PRACTICE...

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66 CHAPTER 4 CHEMICAL REACTIONS PRACTICE EXAMPLES 1A (a) Unbalanced reaction: H 3 PO 4 (aq) + CaO(s) Ca 3 (PO 4 ) 2 (aq) + H 2 O(l) Balance Ca & PO 4 3- : 2 H 3 PO 4 (aq) + 3 CaO(s) Ca 3 (PO 4 ) 2 (aq) + H 2 O(l) Balance H atoms: 2 H 3 PO 4 (aq) + 3 CaO(s) Ca 3 (PO 4 ) 2 (aq) + 3 H 2 O(l) Self Check: 6 H + 2 P + 11 O + 3 Ca 6 H + 2 P + 11 O + 3 Ca (b) Unbalanced reaction: C 3 H 8 (g) + O 2 (g) CO 2 (g) + H 2 O(g) Balance C& H: C 3 H 8 (g) + O 2 (g) 3 CO 2 (g) + 4 H 2 O(g) Balance O atoms: C 3 H 8 (g) + 5 O 2 (g) 3 CO 2 (g) + 4 H 2 O(g) Self Check: 3 C + 8 H + 10 O 3 C + 8 H + 10 O 1B (a) Unbalanced reaction: NH 3 (g) + O 2 (g) NO 2 (g) + H 2 O(g) Balance N and H: NH 3 (g) + O 2 (g) NO 2 (g) + 3/2 H 2 O(g) Balance O atoms: NH 3 (g) + 7/4 O 2 (g) NO 2 (g) + 3/2 H 2 O(g) Multiply by 4 (whole #): 4 NH 3 (g) + 7 O 2 (g) 4 NO 2 (g) + 6 H 2 O(g) Self Check: 4 N + 12 H + 14 O 4 N + 12 H + 14 O (b) Unbalanced reaction: NO 2 (g) + NH 3 (g) N 2 (g) + H 2 O(g) Balance H atoms: NO 2 (g) + 2 NH 3 (g) N 2 (g) + 3 H 2 O(g) Balance O atoms: 3/2 NO 2 (g) + 2 NH 3 (g) N 2 (g) + 3 H 2 O(g) Balance N atoms: 3/2 NO 2 (g) + 2 NH 3 (g) 7/4 N 2 (g) + 3 H 2 O(g) Multiply by 4 (whole #) 6 NO 2 (g) + 8 NH 3 (g) 7 N 2 (g) + 12 H 2 O(g) Self Check: 14 N + 24 H + 12 O 14 N + 24 H + 12 O 2A Unbalanced reaction: HgS(s) + CaO(s) CaS(s) + CaSO 4 (s) + Hg(l) Balance O atoms: HgS(s) + 4 CaO(s) CaS(s) + CaSO 4 (s) + Hg(l) Balance Ca atoms: HgS(s) + 4 CaO(s) 3 CaS(s) + CaSO 4 (s) + Hg(l) Balance S atoms: 4 HgS(s) + 4 CaO(s) 3 CaS(s) + CaSO 4 (s) + Hg(l) Balance Hg atoms: 4 HgS(s) + 4 CaO(s) 3 CaS(s) + CaSO 4 (s) + 4 Hg(l) Self Check: 4 Hg + 4 S + 4 O + 4 Ca 4 Hg + 4 S + 4 O + 4 Ca
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Chapter 4: Chemical Reactions 67 2B Unbalanced reaction: C 7 H 6 O 2 S(l) + O 2 (g) CO 2 (g) + H 2 O(l) + SO 2 (g) Balance C atoms: C 7 H 6 O 2 S(l) + O 2 (g) 7 CO 2 (g) + H 2 O(l) + SO 2 (g) Balance S atoms: C 7 H 6 O 2 S(l) + O 2 (g) 7 CO 2 (g) + H 2 O(l) + SO 2 (g) Balance H atoms: C 7 H 6 O 2 S(l) + O 2 (g) 7 CO 2 (g) + 3 H 2 O(l) + SO 2 (g) Balance O atoms: C 7 H 6 O 2 S(l) + 8.5 O 2 (g) 7 CO 2 (g) + 3 H 2 O(l) + SO 2 (g) Multiply by 2 (whole #): 2 C 7 H 6 O 2 S(l) + 17 O 2 (g) 14 CO 2 (g) + 6 H 2 O(l) + 2 SO 2 (g) Self Check: 14 C + 12 H + 2 S + 38 O 14 C + 12 H + 2 S + 38 O 3A The balanced chemical equation provides the factor needed to convert from moles KClO 3 to moles O 2 . Amount Om o l K C l O mol O mol KClO mol O 23 2 3 2 =1.76 3 2 =2.64 3B First, find the molar mass of Ag O 2 .  2mol Ag 107.87g Ag +16.00g O = 231.74 2 g Ag O / mol amount Ag kg Ag O g kg mol Ag O g Ag O mol Ag mol Ag O mol Ag =1.00 1000 1.00 1 231.74 2 1 =8.63 2 2 22  4A The balanced chemical equation provides the factor to convert from amount of Mg to amount of Mg N 32 . First we must determine the molar mass of Mg N .   molar mass = 3mol Mg 24.305g Mg + 2mol N 14.007g N = 100.93g Mg N 1mol Mg N 100.93g Mg N 1mol Mg mass Mg N = 3.82g Mg = 5.29g Mg N 24.31g Mg 3mol Mg 1mol Mg N 4B The pivotal conversion is from   2 Hg to CH OH 3 (l). For this we use the balanced equation, which requires that we use the amounts in moles of both substances. The solution involves converting to and from amounts, using molar masses.
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04_Petrucci10e_SSM - CHAPTER 4 CHEMICAL REACTIONS PRACTICE...

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