combinepdf-2.pdf - CHEM 230 W16 PREP Final Exam KEY p1 14a Carbonated water is prepared by cooling water to 8.0oC and pressurizing water with a PCO2 of

combinepdf-2.pdf - CHEM 230 W16 PREP Final Exam KEY p1 14a...

This preview shows page 1 - 4 out of 100 pages.

CHEM 230 W16 PREP Final Exam KEY p1 14a) Carbonated water is prepared by cooling water to 8.0 o C and pressurizing water with a P CO2 of 8.3 bar. I wanted to find the solubility of CO 2 at this temperature, but I could not find a value for k H (the Henry's law constant) at 8.0 o C. However, I found the mole fraction of CO 2 in water water to be 0.002771 at 8.0 o C when the partial pressure of CO 2 was 8.3 bar. What is the solubility (molarity) of carbon dioxide under these conditions given a solution density of 0.997g/mL? pick 100 moles total: 0.002771 = molCO 2 mol total = mol CO 2 100 0.2771 molCO 2 44 gCO 2 1 molCO 2 " # $ % & ' = 12.19 gCO 2 100 0.2771 = 99.723 molH 2 O 18 gH 2 O 1 molH 2 O " # $ % & ' = 1795 gH 2 O Total g = 12.19 + 1795 = 1807.1 g total 1 mL solution 0.997g total " # $ % & ' 1 L 1000 mL " # $ % & ' = 1.812 L M = molCO 2 Lsolution " # $ % & ' = 0.2771 mol 1.812 L " # $ % & ' = 0.153 M CO 2 b) Based on the solubility that you found in part a, what is k H for CO 2 in water at 8 o C? [CO 2(aq) ] M 0.153 s = k H P CO 2 0.153 mol L = k H (8.3 bar ) 0.0184 mol Lbar = k H k H mol/(L bar) 0.0184 If the CO 2(g) above the water is removed and replaced by air (N 2(g) and O 2(g) ) at a pressure of 8.3bar, how will each of the following quantities change as the system goes to equilibrium? Circle one answer in each box. c) The [O 2 ] aq will: increase decrease stay the same d) The partial pressure of CO 2(g) will: increase decrease stay the same 15 5 5 5 -3 mistake plugging in or math -3 per math/transcription 0.355 = 4 pts total -5 per conceptual mistke
Image of page 1
CHEM 230 W16 PREP Final Exam KEY p2 15) Three different bases are titrated with 0.1M HCl as described below. Compare the titrations and select the one that best matches the description in parts a-d. Check one column for each row. 10 mL, 0.2 M NH 2 OH pK b = 7.97 10 mL, 0.2 M NH 2 NH 2 pK b = 5.77 10 mL, 0.2 M CH 3 NH 3 pK b = 3.44 b) highest volume of 0.1 M HCl to reach the stoichiometric point All are the same c) lowest pH @ 1/2 stoichiometric point d) highest pH at the stoichiometric point X X X 20 16) a) What is the minimum number of grams of Pb(NO 3 ) 2 (MW= 331.21) that must be added to 100 mL of 5.4x10 -4 M Na 2 SO 4 in order to observe a precipitate? (K sp PbSO 4 = 2.53x10 -8 ) PbSO 4(s) --> Pb +2 (aq) + SO 4 2- (aq) K sp = 2.53x10 -8 K sp = [ Pb 2 + ][ SO 4 2 ] 2.53 x 10 8 = [ Pb 2 + ](5.4 x 10 4 ) 4.68 x 10 5 = [ Pb 2 + ] 4.68 x 10 5 molPb + 2 L 0.1 L # $ % & ' ( 1 molPb ( NO 3 ) 2 1 molPb + 2 # $ % & ' ( 331.21 gPb ( NO 3 ) 2 1 moPb ( NO 3 ) 2 # $ % & ' ( = 1.552 x 10 3 g Pb(NO 3 ) 2 g 1.552x10 -3 10 20 For a saturated aqueous solution of PbSO 4 , describe the response to each of the following stresses. b) adding PbSO 4(s) : PbSO 4(s) will: dissolve precipitate neither cannot determine c) adding NaNO 3(s) : PbSO 4(s) will: dissolve precipitate neither cannot determine d) adding NaNO 3(aq) : PbSO 4(s) will: dissolve precipitate neither cannot determine e) adding Pb(NO 3 ) 2(aq) : PbSO 4(s) will: dissolve precipitate neither cannot determine (Circle one answer in each box.) a) highest initial pH X 3 pts Ksp 4 pts [Pb+2] 3 pts conversion to g
Image of page 2
CHEM 230 W16 PREP Final Exam KEY p3 Ti (s) Cl 2(g) TiCl 4(l) Δ H o f (kJ/mol) S o m (J/K mol) 30.7 223.07 -804.16 221.93 0 a) Write out the balanced chemical equation for the formation of TiCl 4(l) .
Image of page 3
Image of page 4

You've reached the end of your free preview.

Want to read all 100 pages?

  • Spring '14
  • JamesR.Zubricky
  • pH, Chemical reaction, ΔH, kmol

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture