Exam W 1028

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Exam W 10/28

• Review T 10/27 1 pm SL 150

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• Dilution
• When a higher concentration solution is used to
  make a less-concentration solution, the moles of
  solute are determined by the amount of the
  higher-concentration solution. The number of
  moles of solute remains constant.
• MiVi MfVf
• Note
• The units on Vi and Vf must match.

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• A saturated stock solution of NaCl is 6.00 M. How
  much of this stock solution is needed to prepare
  1.00-L of physiological saline soluiton (0.154 M)?

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• Titration
• A procedure for determining the amount of
  substance A by adding a carefully measured volume
  with a known concentration of B until the
  reaction of A and B is just complete

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Figure 4.22C Titration of an unknown amount of
HCl with NaOH (3). Photo courtesy of American
Color.
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• Titration of an unknown amount of HCl with NaOH.
• In the titration above, the indicator changes
  color to indicate when the reaction is just
  complete.

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• Zinc sulfide reacts with hydrochloric acid to
  produce hydrogen sulfide gas
• ZnS(s) 2HCl(aq) ?ZnCl2(aq) H2S(g)
• How many milliliters of 0.0512 M HCl are required
  to react with 0.392 g ZnS?

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• Molar mass of ZnS 97.47 g
• 0.157 L 157 mL HCl solution

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• Quantitative Analysis
• The determination of the amount of a substance or
  species present in a material

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• Gravimetric Analysis
• A type of quantitative analysis in which the
  amount of a species in a material is determined
  by converting the species to a product that can
  be isolated completely and weighed

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• The figure on the right shows the reaction of
  Ba(NO3)2 with K2CrO4 forming the yellow BaCrO4
  precipitate.

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• The BaCrO4 precipitate is being filtered in the
  figure on the right. It can then be dried and
  weighed.

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• A soluble silver compound was analyzed for the
  percentage of silver by adding sodium chloride
  solution to precipitate the silver ion as silver
  chloride. If 1.583 g of silver compound gave
  1.788 g of silver chloride, what is the mass
  percent of silver in the compound?

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Molar mass of silver chloride (AgCl) 143.32 g
1.346 g Ag in the compound
85.03 Ag