stwo Sheet, Data Pase an Aovance stwow for: CHM 2045-L Experiment #5 loentificat
ID: 486233 • Letter: S
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stwo Sheet, Data Pase an Aovance stwow for: CHM 2045-L Experiment #5 loentification of a compown by Mass Relationships NOTE: This document is intended to be a supplement to the experiment in your lab textbook read the discussion in the lab textbook first for a general explanation of the lab! Also, there is an advance s assignment and data page at the end ofthis document which you can useierteadofthe advance study assignment and data pagein your lab textbook. You will receive an unknown which is one of four possible compounds: NaHco, KHCO3, Na2CO3 or K2CO3. The purpose of the experiment is to determine which of these four you have as an unknown The final identification of the compound is based on the value of "Q" as defined on the first page of the experiment in your lab textbook: mass of final chloride mass of original unknown) mass of original unknown There is a theoretical value ofQ and an experimental value of Q. The theoretical value of Q is based on a stoichiometry calculation similar to those done in class in Chapter 3 of the lecture textbook. All of the unknowns end up as a chloride salt at the end of the experiment. Depending on which of the four possible unknowns you have, there are four possible chemical reactions that you will perform the lab: If unknown is NaHCO3, then the overall reaction in the experiment is shown below. This is the NET or the SUM reaction for both parts of the experiment NaHCO HCI NaCl CO2 H2O If unknown is KHCO, then the overall reaction in the experiment is KHCO, HCI KCI co H20 If unknown is Na CO, then the overall reaction in the experiment is: Na2CO 2 HCI 2 NaCl CO2 H20 If unknown is Kacoa, then the overall reaction in the experiment is K2CO3 2 HCI 2 KCI CO2 H20 Note that these are the ovERALL chemical reactions for the entire lab; including the heating process AND the reaction with HCI. For the carbonate salts, the above equationsExplanation / Answer
1. Chloride analysis
a. The unknown is an hydrogen carbonate salt as the chnage in mass is equivalent to addition of one chloride to the salt.
b. The unknown salt could be, NaHCO3 or KHCO3
c. theoretical yield of NaCl from NaHCO3
= 0.5113 x 58.44/84 = 0.36 g
d. theoretical yield of KCl from KHCO3
= 0.5113 x 74.55/100 = 0.38 g
e. theoretical Q value for sodium salt
= (0.36 - 0.5113)/0.5113 = 0.30
f. theoretical Q value for potassium salt
= (0.38 - 0.5113)/0.5113 = 0.25
g. Experimental value of Q
= (0.5640-0.5113)/0.5113 = 0.10
h. The student had KHCO3
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