Chemistry I
Part B (Comprehensive Questions: 20 points) ;
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36.A 1.345 g sample of a compound of barium and oxygen was dissolved in hydrochloric acid to give a solution of barium ion, which was then precipitated with an excess of potassium chromate to give 2.012 g of barium chromate, BaCrO4. ; What is the formula of the compound?(4 points)
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37a. Phenol, commonly known as carbolic acid, was used by Joseph Lister as an antiseptic for surgery in 1865. ; Its principle use today is the manufacture of phenolic resins and plastics. ; Combustion of 5.23 mg of phenol yields 14.67 mg CO2 and 3.01 mg H2O. ; Phenol contains only C, H, and O. ; What is the percentage of each element in this substance?(2 points)
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37.b.How many milliliters of 0.250 M KMnO4 are needed to react with 4.40 g of iron(II) sulfate, FeSO4? (Hint: Volumetric analysis)
The reaction is as follows:
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10FeSO4(aq) + 2KMnO4(aq) + 8H2SO4(aq) ; ;
5Fe2(SO4)3(aq) + 2MnSO4(aq) + K2SO4(aq) + 8H2O(l)
(2 points)
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38.Two compounds have the same composition: 85.62% C and 14.38% H.
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. a. Obtain the empirical formula corresponding to this composition.
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b. One of the compounds has a molecular mass of 28.03 amu; the other, of 56.06 amu. ; Obtain the molecular formulas of both compounds.( 4 points)
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39.a.For the given aqueous reaction, write the molecular and net ionic equations, including phase labels..(2 points)
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The neutralization of acetic acid by calcium hydroxide, both in aqueous solution
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39.b.Balance the following oxidation-reduction reaction by the half-reaction method…(2 points)
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FeI3(aq) + Mg(s) ; ; ; Fe(s) + MgI2(aq)
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40.a.One step in the isolation of pure rhodium metal (Rh) is the precipitation of rhodium(III) hydroxide from a solution containing rhodium(III) sulfate according to the following balanced chemical equation:
Rh2(SO4)3(aq) ;+ ;6NaOH(aq) ; ; ; ;2Rh(OH)3(s) ;+ ;3Na2SO4(aq)
What is the theoretical yield of rhodium(III) hydroxide from the reaction of 0.590 ;g of rhodium(III) sulfate with 0.366 ;g of sodium hydroxide? ; Show detailed work.
(3 points)
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40.b. ; Using questions 40a, calculate the percentage yield ofrhodium(III) hydroxide, Rh(OH)3 ; given that the actual yield ofRh(OH)3 is 0.320 g. ; ; ;
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