Experiment 3 Mass % Water

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Experiment 3 Mass Water
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Reminders

• Always calculate standard deviation when
  calculating average values
• Always calculate absolute error when you are
  able to compare to an actual standard (or
  theoretical) value

3
Goals

• To determine the H2O lost from a substance
  (salt hydrate) upon heating
• To draw conclusions based on these results
• Determining which unknown you have based on the
  experimental and theoretical H2O
• Logical error analysis
• Telling why you suspect that your values arent
  the same as the theoretical values is talking
  about errors in the experiment

4
The Experiment

• Each group will perform twice!!

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NOTES

• Be sure to record unknown letter in your notebook
  in a noticeable manner
• Each bench has an unknown
• After experiment, record your value for your
  unknown(A, B, C, or D) in the appropriate column
  of the spreadsheet. You only need to consider
  the class data for your unknown. Give avgS.D.
  for your values and the class values
• DISPOSAL excess unknowns and residue
• LABELED HAZ WASTE CONTAINER IN HOOD

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NOTES contd.

• Handle with tongs, never hands. Why?
• Should we use lids when weighing? Why?
• Should we use lids when heating? Why?

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NOTES contd.

• Clean then heat red hot for 5 min. Why?
• What is a desicooler? Why do we use it?
• Desicooler-
• Desicant-
• Why do you heat sample twice?

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Calculations

• Theoretical H2O the amount of water that
  should be in that substance
• Theor. H2O total mass-mass salt 100
• total mass
• Experimental H2O
• initial sample mass mass of residue 100
• initial sample mass

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Data Table
Determination of Unknown Mass
Items Weighed Mass (g) Mass (g)
Items Weighed Sample 1 Sample 2
Beaker(B) Crucible(C)
B C Sample(S)
Calc. Initial Mass of Sample
B C Residue(R) heated once
B C R heated twice
B C R heated 3 times
Calc. Mass of Residue
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Results Table
Calculated H2O Values

Item H2O
CuSO45H2O
MgSO47H2O
CoCl26H2O
Cu(NO3)24H2O
Unknown A Sample1
Unknown A Sample2
Avg Experimental Unknown A
Class Avg Unknown A
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Experimental Design