Quiz 5 Name: _______________________________________ Chemistry 102, Lecture 402 – Fall 2016 DS Section: (1 point) ____________________________ 1. What is the empirical and molecular formula of a hydrocarbon that contains 84.4% carbon by mass (the remaining mass is hydrogen) and has a molar mass of about 142.3 g∙mol–1? (3 points)  84.4 g C   mol C 
142.3 g total  

  10 mol C
 100 g total   12.01 g C 
 15.6 g H   mol H 

  22 mol H
 100 g total   1.01 g H 
142.3 g total  
molecular formula = C10 H 22
empirical formula  C5 H11
2. In lab this week, you precipitated a number of salts. Using the balanced equation and given information, complete the table. (6 points) Work: 3AgNO3(aq) + Na3PO4(aq)  Ag3PO4(s) + 3NaNO3(aq) molar mass (AgNO3) 169.88 g∙mol–1 molar mass (Na3PO4) 163.94 g∙mol–1 molar mass (Ag3PO4) 418.58 g∙mol–1 mass of AgNO3 15.0 g mass of Na3PO4 6.50 g limiting reactant AgNO3 theoretical yield (of solid) 12.3 g actual yield 10.9 g percent yield 88.97% 
mol AgNO3  1 mol Na 3 PO 4   163.94 g Na 3 PO 4 


  4.83 g Na 3 PO 4
 169.88 g AgNO3  3 mol AgNO3   mol Na 3 PO 4 
Because 4.83 g Na 3 PO 4  need  < 6.50 g Na 3 PO 4  have  , AgNO3 is the limiting reactant.
15.0 g AgNO3  

mol AgNO3  1 mol Ag 3 PO 4  418.58 g Ag 3 PO 4 


  12.3 g Ag 3 PO 4
 169.88 g AgNO3  3 mol AgNO3  mol Ag 3 PO 4 
15.0 g AgNO3  
12.3 g Ag3 PO4
 88.97 g exp 
theo  
  10.9 g experimentally/actual yield
 100 g theo 
3. Give a cation and the correct formula for a carbonate salt that would result in the mixtures shown below. (2 points) Anion: Group 2, 3 or transition metals Formula of salt (as an example): Al2(CO3)3 Anion: Alkali metals, NH4+ Formula of salt (as an example): Na2CO3