Exam III A Solutions

CHM 130 Exam III A Fall 2016 Ch. 10-15 Name: ______KEY_______ Directions. There is only one best answer for multiple-choice questions. All calculations must show work with units for full credit. Good Luck.  1. Answer a-c using this balanced reaction: 2 Al(s) + 6 HCl(aq)  2 AlCl3 (aq) + 3 H2 (g) a. How many moles of hydrogen are produced when 4.25 moles of hydrochloric acid react? 4.25 mol HCl ( 3 mol H2 / 6 mol HCl ) = 2.13 mol H2 b. How many grams of hydrochloric acid are needed to react with 9.35 grams of aluminum? 9.35 g Al ( 1 mol Al / 26.98 g Al)( 6 mol HCl / 2 mol Al)( 36.46 g HCl / 1 mol HCl) = 37.9 g HCl c. How many liters of hydrogen gas at STP are produced from reacting 12.5 grams of aluminum? 12.5 g Al ( 1 mol Al / 26.98 g Al)( 3 mol H2 / 2 mol Al)( 22.4 L H2 / 1 mol H2) = 15.6 L H2 2. Balance and classify these reactions as (C) combination, (D) decomposition, (CB) combustion, (SR) single replacement, (DR) double replacement, and (N) acid base neutralization. type:__ DR _ type:__ D_ type:__ SR_ ____ Na2 CO3 (aq) + ____MgCl2 (aq)  ____ MgCO 3 (s) + _2_ NaCl(aq) ____ P4 O10 (l)  __4 P (s) + _5_ O2 (g) __3__ Ca(s) + __2_ AlCl3 (aq)  __3__ CaCl2 (aq) + __2_ Al(s) 3. Write the products, states, and then balance these reactions. Write NR if no reaction. a. ___C5 H8 (l) + __7_O2 (g)  _________5 CO2(g) + 4 H 2O(g) ____________ b. ___Cu(s) + ___MnBr2 (aq)  _________NR_________________________________ c. __2_HI(aq) + ___Sr(OH)2 (aq)  ______2 H 2O(l) + SrI2 (aq) _____________ d. _2__Al(s) + __3_Ni(NO 3 )2 (aq)  ________3 Ni(s) + 2 Al(NO3)3 (aq) ____________ 4. Consider this reaction: 2 AgCl(aq) + Cd(s)  CdCl2 (aq) + 2 Ag(s) a. What is reduced? ___ Ag in AgCl(aq) ___ b. What is oxidized? _____ Cd(s) ______ 5. What holds the sulfur atom to the hydrogen atom in one molecule of hydrogen sulfide gas, H2 S , the gas partly responsible for the rotten egg smell and flatulence? a. Ionic bonds b. polar covalent bonds c. H bridge force d. dipole-dipole forces e. nonpolar covalent bonds 6. What holds HF molecules with other HF molecules? a. London forces b. polar covalent bonds e. nonpolar covalent bonds c. H bridge force d. dipole-dipole forces 7. What holds Br2 molecules with other Br2 molecules in liquid bromine? a. London forces b. polar covalent bonds e. nonpolar covalent bonds c. H bridge force d. dipole-dipole forces 8. Answer the following based on the comparison of liquid butane, C4 H10 , and liquid butanol, C4 H9 OH? a. Which has the higher IMF? ___butanol_____ b. Which has the higher Vapor Pressure? __butane____ c. Which has the lower boiling point? ___butane____ d. Which has the higher surface tension? __butanol____ e. Which has the lower viscosity? ___butane_____ 9. What is the highest IMF you expect to see in samples of millions of molecules of: a. HBr _dipole-dipole____ b. H2 O___H-bridging_____ c. Cl2 _____London___ 10. Answer the following according to this heating curve graph below. a. At which point is melting or freezing occurring? ____B____ b. At which point is there liquid only? _______C______ c. At which point is there solid only? _____A________ d. At which point is boiling or condensation occurring? ______D______ 11. A solution is defined as a _________solute________ dissolved in a ___solvent___. 12. Which of the following is most likely to dissolve in benzene, C 6 H6 (l)? a. NaCl b. N 2 c. NH3 d. HF e. Na2 SO4 13. Popular as a salad dressing, vinegar and oil don’t mix so we call them: a. soluble b. insoluble c. miscible d. immiscible e. undissolved 14. What is the mass % if 87.45 grams of KOH is dissolved in 238 grams of water? % = 87.45 / (87.45 + 238) x 100 = 26.9 % 15. Calculate the molarity if 1.525 grams of NaC2 H3 O 2 , is dissolved in 755 mL of water. mol = 1.525 g ( 1 mol / 82.04 g ) = 0.018588493 mol L solution = 755 mL ( 1 L / 1000 mL) = 0.755 L M = 0.018588493 mol / 0.755 L = 0.0246 mol/L 16. How many moles are in 6.15 x 1024 atoms of calcium? 6.15 x 1024 atoms Ca ( 1 mol / 6.02 x 1023 atoms) = 10.2 mol Ca 17. How many grams are in 0.8735 moles of AgNO 3 ? 0.8735 mol AgNO3 ( 169.88 g / mol) = 148.4 g AgNO3 18. How many liters are in 55.3 grams of CO 2 gas at STP? 55.3 g CO2 ( 1 mol / 44.01 g) ( 22.4 L / 1 mol) = 28.1 L CO2 Bonus: How many atoms of sodium are in 22.99 grams? (No calculations needed) 6.02 x 1023 atoms _