College Prep Chemistry
50 points
Core
Lab #8
Determination of the Percent of Water in Hydrated Copper Sulfate
Objective:
To determine the percent water in copper (II) sulfate pentahydrate
.
Reaction:
Hypothesis:
Procedure:
a. ***Safety reminder – you will utilize a Bunsen burner, glass labware, and handle hot objects – ensure that long
hair is tied back along with loose clothes and jewelry. You must also have closed toed shoes and safety glasses
on throughout the entirety of this laboratory procedure. ***
b. Complete the observations for Table 2 as the lab progresses.
c. Light the Bunsen burner and begin slowly heating a cleaned crucible for about 4 minutes. While one lab
partner remains with the lit Bunsen burner another should obtain about a 3 g sample of crushed copper (II)
tahydrate.
sulfate pen
d. Carefully obtain and record the mass of the sample.
e. After 3 minutes of moderate heating turn the Bunsen burner off and allow the crucible to cool. When cooled
enough (ask instructor if unsure) obtain the mass of the crucible.
f.
Slowly and carefully place the sample into the crucible and begin slowly heating the crucible. A glass stir
rod may be used to gently spread the sample as it’s heated. Ensure that any sample that sticks to the stir
rod is not lost.
g. If the sample spatters or starts to turn brown – lower the heat being applied. Continue to heat the sample
until the color change is complete. Allow the crucible to cool then obtain the mass of the crucible.
h. Heat the sample again for another 3 minutes, allow to cool, and then obtain it’s mass. If the second mass
matches the first mass to within 0.04g then you are finished heating. If the two masses differ, heat and cool
the sample a third time
i.
j.
– DO NOT stir the sample during this third heating.
Once all data is recorded, slowly place a few drops of water onto the cooled sample. Record any
observations.
Lastly, clean all labware, wipe down the entire lab bench, and double check that all gas valves are closed.
Data:
Table 1:
________________________________
Mass of Empty Crucible
Mass of CuSO4
• 5H2
O Sample
Mass of Crucible and CuSO4 after 1st Heating
Mass of Crucible and CuSO4 after 2nd Heating
**Mass of Crucible and CuSO4 after 3rd Heating***
Mass of Crucible and CuSO4 after Final Heating
(May be the 2nd or 3rd heating)
Mass of CuSO4
Mass of H2O Lost
Table 2:
___________________________________
Hydrate
(Before heating)
Anhydrate
(After heating)
Hydrate
(After adding drops of water)
Analysis:
1.
Show all calculations:
•
•
•
•
2.
3.
Calculate the mass of CuSO4 after the final heating
Calculate the mass of water lost
Calculate the percent of water in your sample from experimental data
Calculate percent of water in sample based on the chemical formula (actual value)
Stem and Leaf Plot and determine median class value (experimental value)
Calculate Percentage Error
Results:
•
•
•
Identify and report the class value and the actual value for the percent water in hydrated copper(II) sulfate
Report the percent error
Sentence format
Conclusion:
•
See rubric for guidelines
RST:
Two apprentice jewelers are given the task of shipping opals to client who lives across the country.
An argument ensues over how to ship the opals. One apprentice says to wrap them in bubble wrap and seal them
in a manila envelope. The other apprentice wants to wrap the opals in damp cotton and ship them in a Styrofoam
box.
In this lab, you determined the percentage of water in a hydrated compound. You will analyze your data and
results (Source A), Section 10.5 in the text (Source B), and the paragraph below (Source C) to gather information
and formulate a written argument solving the problems of how to ship the opals so they arrive at the destination in
the best possible condition
.
Source C: (Excerpt from Chemistry Matters 2012)
Some opals with orange-red coloring are referred to as fire opals. The greater the water concentration in the opal,
the greater the fire coloring appears. Some fire opals have up to 10% water by mass. Opals often crack when
stored at high temperatures.
College Prep Chemistry
Core Lab #8
50 points
Determination of the Percent of Water in
Hydrated Copper (II) Sulfate Rubric
Format
• Written in pencil (1)
• Listed in table of contents (1)
• Underline appropriate titles (1)
• No personal pronouns (1)
• Lines skipped in written sections (1)
• Use appropriate units throughout and significant digits (2)
• Title all tables, graph, and figures (1)
• Tables and graphs are drawn with straight edge (1)
9 points
Introductory Paragraph/ Pre-lab Questions
• Pre-lab questions answered correctly (2)
• Hypothesis written appropriately (2)
• Restate the objective and incorporate how the objective was met by performing this lab (2)
o Use definitions appropriately.
• Address the objectives. Support your answer with lab data and results (3)
• Defend the hypothesis (1)
10 points
Data /Analysis
• Table 1 & 2 completed appropriately (2)
• Calculations (3)
o Work shown
o Correct answer
o Significant figures used
• Stem and Leaf (2)
o Scale
o Key
• Summary data table (2)
o n, R, median
• Percent Error (2)
o Formula, substitution, and answer
8 points
Conclusion
13 points
• Restate the objective and incorporate how the objective was met by performing this lab (4)
o Definition(s)
• Address the objective. Support your answer with lab data and results (3)
• Identify 2 sources of error and the effect they would have on the experiment (3)
o Source of error
o Effect on data
o Effect on result
• Conclusion quality: well organized and cohesive and contains no mechanical/grammatical errors. (3)
o Well organized and cohesive but contains grammatical or mechanic (2)
o Somewhat organized but does not contain any errors (2)
o Somewhat organized with some errors (1)
o Disorganized with errors (0)
RST
10 points
•
•
•
•
Thesis statement (2)
Comprehension of key ideas and details (3)
o Cites convincing evidence to support analysis, showing full comprehension of complex ideas
expressed in the texts provided.
Development of ideas and organization (2)
o Student response addresses the prompt and provides effective development of the claim by using
clear and convincing reasoning, details, and evidence.
Appropriate integration of source material/information (3)
o Student response utilizes information in a way where the sources “speak with one another” are
used adequately to support the student’s claims and lab conclusions.