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Aqueous Reactions and Solution Stoichiometry (Chapter 4) Past Quizzes and Tests My answers are in bold-faced underlined italics. 1. 2. 3. 4. How many moles of Ca(NO3)2 are contained in 150.0-mL of a 0.245-M solution of Ca(NO3)2? 150.0mL 0.245molCa ( NO3 ) 2 ? molCa ( NO3 ) 2 = x = 0.03675molCa ( NO3 ) 2 1 1000mL How many grams of KCl are required to make 450.0-mL of a solution that is 0.100-M KCl? 450.0mL 0.100molKCl 74.5KCl ? gKCl = x x = 3.353gKCl 1 1000mL 1molKCl 34.5-g of BaBr2 are dissolved in water to make a solution that has a total volume of 750.0-mL. What is the molarity of BaBr2, Ba2+, and Br- in the solution? 34.5 gBaBr2 # molsolute 297 g / mol M = = = 0.155MBaBr2 # LSolution 0.750 L For the molarity of the other species, realize that each mol of BaBr2 provides one mol of Ba2+ and 2 mol of Br-. Their concentrations are 1x0.155M = 0.155 M Ba2+ and 2 x 0.155 M = 0.310 M Br-. 0.415-g of potassium hydrogen phthalate are dissolved in water and phenolphthalein indicator added. The equivalence point is reached with the addition of 31.95-mL of a NaOH solution. What is the molarity of the NaOH solution? (Molar mass of KHP = 204.1 g/mol) Potassium hydrogen phthalate, KHC8H4O4, reacts with NaOH according to the equation: KHC8H4O4 (aq) + NaOH (aq) 6 NaKC8H4O4 (aq) + HOH (R) From the equation, note that one mole of KHC8H4O4 reacts with 1 mol of NaOH. So, if we know how many mol of KHC8H4O4 were in the flask initially, we can determine the number of moles of NaOH in the volume of NaOH delivered. # molKHC8 H 4O4 = 0.415 gKHC8 H 4O4 = 2.03x10 −3 molKHC8 H 4O4 204.1g / mol so # molNaOH = 2.03x10 −3 molNaOH so M NaOH # molNaOH 2.03x10 −3 molNaOH = = = 6.36 x10 −2 MNaOH # LNaOH 0.03195Lsolution 5. 6. Find the oxidation number of the underlined element in each of the following species. AsO43- +5 Ba(NO2)2 +3 NH4+ HCO3 G -3 N2O5 +5 +4 Complete and balance the following equations. Also write the total ionic and net ionic equations for each. 3 SrCl2 (aq) + 2 Na3PO4 (aq) ------> Sr3(PO4)2 (s) + 6 NaCl (aq) Total Ionic: 3 Sr2+ (aq) + 6 Cl- (aq) + 6 Na+ (aq) + 2 PO43- (aq) Æ Sr3(PO4)2 (s) + 6Na+ (aq) + 6 Cl- (aq) Net Ionic: 3 Sr2+ (aq) + 2 PO43- (aq) Æ Sr3(PO4)2 (s) 3 Li (s) + FeCl3 (aq) ----> 3 LiCl (aq) + Fe (s) Total Ionic: 3 Li (s) + Fe3+ (aq) + 3 Cl- (aq) Æ 3 Li+ (aq) + 3 Cl- (aq) + Fe (s) Net Ionic: 7. 3 Li (s) + Fe3+ (aq) Æ 3 Li+ (aq) + Fe (s) Classify each of the following as to whether it is a salt, acid, or base (S/A/B); soluble or insoluble (S/I); and strong or weak/non electrolyte (S/W). Compound A/B/S S/I S/W Compound A/B/S S/I S/W HNO2 A S W PbBr2 S I S BaSO4 S I S Cu(NO3)2 S S S HC2H3O2 A S W Fe2O3 S I S H2C8H4O4 A S W (NH4)2S S S S Fe(OH)3 B I S H2S A S W 8. Complete the following metathesis reaction and write the total ionic equation and the net ionic equation. Molecular equation: CaCl2 (aq) + Pb(NO3)2 (aq) -----> Ca(NO3)2 (aq) + PbCl2 (s) Total Ionic: Ca2+ (aq) + 2 Cl- (aq) + Pb2+ (aq) + 2 NO3- (aq) Æ Ca2+ (aq) + 2 NO3- (aq) + PbCl2 (s) Net Ionic: 9. 2 Cl- (aq) + Pb2+ (aq) Æ PbCl2 (s) Complete and balance the following metathesis reactions. Further write the total ionic and net ionic equations for each: 3 BaCl2 (aq) + 2 Na3PO4 (aq) Æ Ba3(PO4)2 (s) + 6 NaCl (aq) Total Ionic: 3 Ba2+(aq) + 6 Cl-(aq) + 6 Na+ (aq) + 2 PO43- (aq) Æ Ba3(PO4)2 (s) + 6 Na+ (aq) + 6 Cl-(aq) Net Ionic: 3 Ba2+(aq) + 2 PO43- (aq) Æ Ba3(PO4)2 (s) HC2H3O2 (aq) + KOH (aq) Æ HOH (R) + K C2H3O2 (aq) Total Ionic: HC2H3O2 (aq) + K+ (aq) + OH- (aq) Æ HOH (R) + K+(aq) + C2H3O2- (aq) Net Ionic: 10. HC2H3O2 (aq) + OH- (aq) Æ HOH (R) + C2H3O2- (aq) Classify each of the following solutes as acids, bases, or salts. For each indicate whether it is a strong or weak/non electrolyte (SE or WE) and whether the substance is soluble (S) or insoluble (I) in aqueous solution. H2SO3 Acid, weak, soluble Ba3(PO4)2 Salt, Strong, Insoluble NaCl Salt, Strong, Soluble NH4Cl Salt, Strong, Soluble BaBr2 Salt, Strong, Soluble 11. For each of the following: a. State whether it is an acid(A), base(B), or salt(S). b. State whether it is a strong electrolyte (SE) or weak/nonelectrolyte(WE) c. State whether it is soluble (S) or insoluble (I). Substance Acid(A)/Base(S)/Salt(S) Strong Electrolyte (SE)/Weak Electrolyte (WE) Soluble (S)/Insoluble (I) KCl S SE S (NH4)2S S SE S HNO2 A WE S PbCl2 S SE I Fe(OH)3 B SE I Ba3(PO4)2 S SE I HClO4 A SE S HBrO A WE S Ba(C2H3O2)2 S SE S Mg(OH)2 B SE I 12. Classify each of the following reactions as to whether it is combustion, decomposition, combination, metathesis, or oxidation-reduction. Note some equations may fall into more than one category. State all categories that apply in each case. Equation 2 NaHCO3 (s) ----> Na2CO3 (s) + H2O (R) + CO2 (g) BaO (s) + H2O (R) ----> Ba(OH)2 (aq) Ba(NO3)2 (aq) + Na2SO4 (aq) ----> BaSO4 (s) + 2 NaNO3 (aq) Cu (s) + 2 AgNO3 (aq) ----> 2 Ag (s) + Cu(NO3)2 (aq) CH4 (g) + 2 O2 (g) —> CO2 (g) + 2 H2O (R) Classification decomposition combination metathesis oxidation-reduction combustion, oxidationreduction 13. Complete and balance each of the methathesis equations below and write the total ionic and net ionic equation for each. H2SO4 (aq) + Complete equation: H2SO4 (aq) + 2 NaOH (aq) 2 NaOH (aq) -----> -----> HOH (ℓ) + Na2SO4 (aq) Total ionic equation: 2 H+ (aq) + SO42- (aq) + 2 Na+ (aq) + 2 OH- (aq) Æ HOH (ℓ) + 2 Na+ (aq) + SO42- (aq) Net ionic equation: 2 H+ (aq) + 2 OH- (aq) Æ HOH (ℓ) BaCl2 (aq) + Pb(NO3)2 Æ Complete equation: Pb(NO3)2 Æ BaCl2 (aq) + Ba(NO3)2 (aq) + PbCl2 (s) Total ionic equation: Ba2+ (aq) + 2 Cl- (aq) + Pb2+ (aq) + 2 NO3- (aq) Æ Ba2+ (aq) + 2 NO3- (aq) + PbCl2 (s) Net ionic equation: 14. a. 2 Cl- (aq) + Pb2+ (aq) Æ PbCl2 (s) In the standardization reaction of a solution of NaOH, 0.4529-g of potassium hydrogen phthalate (molar mass = 204.2) is weighed into an Erlenmeyer flask. Water and phenolphthalein are added to the flask to dissolve the phthalate and provide an indicator for the titration. 34.75-mL of the NaOH solution were required to reach the endpoint in the titration between the potassium hydrogen phthalate and the NaOH. What is the molarity of the NaOH solution? # molKHP = 0.4529 gKHP = 0.002218molKHP 204.2 g # molKHP = # molNaOH = 0.002218molNaOH MNaOH = b. 0.002218molNaOH = 0.06383MNaOH 0.03475L The same NaOH solution from part a is used to titrate 25.00-mL of a H2SO4 solution. The titration requires 29.45-mL of the NaOH solution. What is the molarity of the H2SO4? # molNaOH = 0.02945 LNaOHSolution x 0.06383MNaOH = 0.001880molNaOH 1 x # molNaOH = 0.0009399 2 0.0009399molH 2 SO4 MH 2 SO4 = = 0.03760 M 0.025Lsolution #molH 2 SO4 = 15. Indicate for each of the following aqueous solutions whether there would be a precipitate formed upon mixing or not. If a precipitate is formed indicate the formula and name for the precipitate. (Hint: Think metathesis) a. b. c. d. e. 16. Pb(NO3)2 and KCl Yes; PbCl2; lead (II) chloride BaBr2 and NH4NO3 No; both Ba(NO3)2 and NH4Br are soluble AgNO3 and CaCl2 Yes; AgCl; silver chloride BaCl2 C2H2O and Na3PO4 C12 H2O Yes; Ba3(PO4)2; barium phosphate KBr and NaCl No; both KCl and NaBr are soluble For one of the reactions that forms a precipitate in question 15: a. Write the balanced chemical equation. b. Write the total ionic equation. c. Write the net ionic equation. For reaction a of problem 15: Total molecular equation: Pb(NO3)2 (aq) + 2 KCl (aq) Æ PbCl2 (s) + 2 KNO3 (aq) Total ionic equation: Pb2+ (aq) + 2 NO3- (aq) + 2 K+(aq) + 2 Cl- (aq) Æ PbCl2 (s) + 2 K+ (aq) + 2 NO3- (aq) Net ionic equation: 17. Pb2+ (aq) + 2 Cl- (aq) Æ PbCl2 (s) Balance each of the following equations and classify it as combustion, decomposition, combination, methathesis, and/or oxidation-reduction. Note that some equations may fall into more than one category. State all categories that apply in each case. Equation 2 C(gr) + ___ O2 (g) Æ 2 CO (g) Classification combustion and redox ___ NH3 (g) + ___ HCl (g) Æ ___ NH4Cl (s) combination ___ Cr(s) + ___ NiSO4 (aq) Æ ___ Ni (s) + ___ CrSO4 (aq) redox ___ HC2H3O2 (aq) + ___NaOH(aq) Æ ___ HOH (R) + ___ NaC2H3O2 (aq) metathesis 2 H2O (R) Æ 2 H2 (g) + ___ O2 (g) 18. _decomposition/redox Classify each of the following as an acid (A), base (B), or salt (S). Further classify each as to whether it is a strong electrolyte (SE) or weak/non electrolyte (WE). HBr Acid,SE Cu(OH)2 Base, SE BaSO4 Salt,SE Mn(NO3)2 Salt, SE NaOH Base, SE K2C2O4 NH4Cl Salt,SE NaF Salt, SE AgCl Salt,SE BaBr2 Salt, SE Salt, SE 19. Complete and balance each of the following metathesis reactions. Further write the total ionic and net ionic equation for each. a. Molecular: Ba(NO3)2 (aq) + Na2SO4 (aq) Æ BaSO4 (s) + 2 NaNO3 (aq) Total Ionic: Ba2+ (aq) + 2 NO3- (aq) + 2 Na+ (aq) + SO42- (aq) Æ BaSO4 (s) + 2 Na+ (aq) + 2 NO3- (aq) Net Ionic: b. Molecular: Ba2+ (aq) + SO42- (aq) Æ BaSO4 (s) 2 HCl (aq) + Ba(OH)2 (aq) Æ 2HOH (ℓ) + BaCl2 (aq) Total Ionic: 2H (aq) + 2Cl- (aq) + Ba2+ (aq) + 2 OH- (aq) Æ 2HOH (ℓ) + Ba2+ (aq) + 2 Cl- (aq) + Net Ionic: 20. 2H+ (aq) + 2 OH- (aq) Æ 2HOH (ℓ) Or + H (aq) + OH (aq) Æ HOH (ℓ) 30.00-mL of a 0.130-M solution of AgNO3 is mixed with 20.00-mL of a 0.120-M solution of BaCl2. How many grams of AgCl could be formed in this process? Since we are given amounts of two reactants, we need to figure out which one is the limiting reactant The problem involves determining which reactant will be used up. The determination of the limiting reactant requires determining how many moles of each reactant are present in the mixture. This is done by multiplying the number of liters by the molarity of the respective solution. # molAgNO3 = 0.0300 Lx0.130 MAgNO3 = 0.003900molAgNO3 # molBaCl2 = 0.0200 Lx0.120 M = 0.002400molBaCl2 0.003900 mol AgNO3 0.002400 mol BaCl2 2 AgNO3 (aq) + BaCl2 (aq) Æ 2 AgCl (s) 2 mol AgNO3 2 x 169 g AgNO3 1 mol BaCl2 1 x 208 g BaCl2 2 mol AgCl 2 x 142.5 g AgCl + Ba(NO3)2 (aq) 1 mol Ba(NO3)2 1 x 261 g Ba(NO3)2 To check for limiting reactant, compare the two ratios: 0.003900molAgNO3 0.002400molBaCl2 = 0.001950 = 0.002400 2molAgNO3 1molBaCl2 Since the AgNO3 ratio is lower, it is the limiting reactant. To find the grams of AgCl, use the AgNO3 since it is limiting. # gAgCl = 0.0039molAgNO3 2 x142.5 gAgCl x = 0.5558gAgCl 1 2molAgNO3 21. Identify each of the following as an acid, base, or salt. Further identify each as a strong electrolyte (SE) or weak/non electrolyte (WE). Ba(NO3)2 Salt,SE 22. LiOH Base,SE HNO2 Acid,WE HF Acid,WE Ca(C2H3O2)2 Salt,SE Label each of the following as an acid, base, or salt. Further identify each as a strong electrolyte (SE), or a weak/non electrolyte (WE). Ba(NO3)2 Salt;SE CaBr2 Salt;SE HC2H3O2 Acid;WE HF LiOH Base;SE HOH A/B;WE HNO2 Acid;WE Cu(OH)2 Base;SE RbC8H14O2 Salt;SE 23. Acid;WE Ba3(PO4)2 Salt;SE 25.00-mL of 0.10 M HCl are mixed with 35.00 mL of 0.15 M Pb(NO3)2. a. Write a balanced chemical equation for this metathesis reaction. 2 HCl (aq) + Pb(NO3)2 (aq) Æ 2 HNO3 (aq) + PbCl2 (s) b. Which is the limiting reactant? Check number of moles of each: # mol HCl = 0.025L x 0.20 M HCl = 0.0050 mol HCl # mol Pb(NO3)2 = 0.035 L x 0.15 M Pb(NO3)2 = 0.00525 mol Pb(NO3)2 Need twice as many mol of HCl as Pb(NO3)2, meaning we would need 2 x 0.00525 mol Pb(NO3)2 which is 0.01050 mol of the HCl. There is not enough. HCl is limiting. c. How many grams of PbCl2 could be formed in the reaction? Use the HCl since it is limiting. # molPbCl2 = 0.0050molHCl 1x 278 gPbCl2 x = 0.695 gPbCl2 1 2molHCl 24. Balance each of the following equations. Also classify each as to whether it is combination, decomposition, single displacement, metathesis, or redox. Some equations may fall into more than one category. Be sure to list all categories that apply for each equation. Classification(s) 2SO3 (g) 6 2SO2 (g) + ___ O2 (g) ___ BI3 + ___ GaF3 ___ P4 + 5 O2 2 C4H10 + 13 O2 25. 6 decomposition,redox ___ BF3 + ___ GaI3 6 ___ P4O10 6 8 CO2 + 10 H2O metathesis combination,redox combustion,redox ___ Zn + 2 HCl 6 ___ ZnCl2 + ___ H2 displacement,redox Complete and balance the following metathesis reactions. Further write the total ionic and net ionic equation for each. BaCO3 (s) + 6 Ba(NO3)2 (aq) 2 HNO3 (aq) + H2CO3 (aq) Total Ionic: BaCO3 (s) + 2 H+ (aq) + 2 NO3- (aq) Æ Ba2+ (aq) + 2 NO3- (aq) + H2CO3 (aq) Net Ionic: BaCO3 (s) + 2 H+ (aq) Æ Ba2+ (aq) + H2CO3 (aq) (Note: In water, the H2CO3 breaks into water and carbon dioxide – you would see bubbles coming off) H2SO4 (aq) + 2 NaOH (aq) 6 Na2SO4 (aq) + 2 HOH (ℓ) Total Ionic: 2 H+ (aq) + SO42- (aq) + 2 Na+ (aq) + 2 OH- (aq) Æ 2 Na2+ (aq) + SO42- (aq) + 2 HOH (ℓ) Net Ionic: 2 H+ (aq) + 2 OH- (aq) Æ 2 HOH (ℓ) Or H+ (aq) + OH- (aq) Æ HOH (ℓ) 26. 125.0-mL of 0.183 M HNO3 is diluted with water to 500.0-mL in a volumetric flask. What is the new concentration of the HNO3? M 1V1 = M 2V2 0.183Mx125.0mL = M 2 x500.0mL M2 = 0.183Mx125.0mL = 0.458M 500.0mL