Statistics- CHEM:1110‐ Principles of Chemistry I, Spring 2016

| March 31, 2017

Question
CHEM:1110‐ Principles of Chemistry I, Spring 2016

IV Pre-Laboratory Activity (Topic 2)
.
Reminder: You will turn in a copy of your pre-lab as soon as you walk into the laboratory.
1. Look up the Material Safety Data Sheet (MSDS) for the chemicals that you will use
in experiment 2. (http://icon.uiowa.edu) Read the pertinent information about all
of the chemicals that are used in this experiment. List all chemicals (and only those
chemicals) that have a health hazard rating of three or greater.
For problems 2 & 3, the density of the sample is 0.9977 g/mL and the molar mass of
calcium carbonate is 100.0 g/mol.
2. Calculate the mass of calcium carbonate present in a 50.00 mL sample of an aqueous
calcium carbonate standard, assuming the standard is known to have a hardness of
75.0 ppm (hardness due to CaCO3).
3. If the 50.00 mL sample from problem 2 above was titrated with a 0.00501 M EDTA,
what volume of EDTA solution would be needed to reach the endpoint? (Your
answer should be given in milliliters. Reminder: this volume what you should expect
for your first sample that you will use to calibrate your expectations.)
4. A group of students titrate a calcium carbonate standard solution repeatedly in six
experimental trials. Based on the six trials, the group determines that the average
concentration of the standard is 75.3 ppm with a standard deviation of 0.6 ppm.
Using the equation for the Student’s t confidence interval found on page 43 of your
lab manual and a t-value of 2.57 for a 95% confidence interval, calculate the
confidence interval for which there is a 95% chance of finding the “true value” of
the standard solution’s concentration based on the data. Put your answer in the
format # lower limit < “true value” < # upper limit. (Page 43 has an example that
may be helpful.)
5. What harmful substance was recently found in the water supply (and in residents’
blood) in Flint, Michigan? Hint: search Flint Water Crisis or see articles such as:
http://www.huffingtonpost.com/entry/obama-flint-watercrisis_us_56a03c39e4b0d8cc1098bf55

Reminder: units and significant figures count on quantitative problems.

33B

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