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please answer all questions and show work. My assignment is due tomorrow at 8am
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Name:_____________________________
Chem 105L Midterm
You must show all your work in order to receive full credit for a question.
1.
Identify each of the following pieces of laboratory equipment. (11 pts)
2.
Name the three safety items you must wear in the laboratory at all times and two additional safety
items located in the laboratory. (5 pts)
PM 3/8/16
Name:_____________________________
3.
A) Using the data given in the table below, calculate the average (15 pts for entire question.
SHOW ALL WORK FOR EACH SECTION FOR FULL CREDIT)
Table1: Standardized mass of weights
Weight of
Experimental
Experimental
standardized
weight of metal
weight of metal
mass (g)
(g)
(g)
Trial 1
Trial 2
10g
9.9483
9.8231
20g
19.9023
19.9842
30g
29.9762
29.9852
Experimental Average
weight of
(g)
metal (g)
Trial 3
9.9725
19.9990
29.9998
B) Calculate the absolute and relative error.
C) Calculate the standard deviation and coefficient of variation.
4.
To identify a liquid substance, a student determined its density. Using a graduated cylinder, she
measured out a 45-mL sample of the substance. She then measured the mass of the sample,
finding that it weighed 38.5 g. What is the calculated density of the substance? (8 pts SHOW ALL
WORK FOR FULL CREDIT)
5.
An object floats in a 7% solution of NaCl but sinks in distilled water. How does the density of the
object compare with the water and with the brine (salt) solution? (8 pts SHOW ALL WORK FOR
FULL CREDIT)
PM 3/8/16
Name:_____________________________
6.
Based on what you’ve learned in Experiment 3 and lecture material, use the differences in the
physical properties of BaSO4 and K2SO4 to develop a procedure for separating a mixture
containing of these compounds. (15 pts SHOW ALL WORK FOR FULL CREDIT)
7.
Find the empirical formula of a compound containing 42.93% carbon and 57.14% oxygen by
weight. (15 pts SHOW ALL WORK FOR FULL CREDIT)
8.
Why was water added to the magnesium after its initial burning in experiment # 4? (8 pts)
9.
The chemical formula of blue copper sulfate is CuSO4•5H2O. Determine the mass percent of
water in blue copper sulfate. (15 pts SHOW ALL WORK FOR FULL CREDIT)
PM 3/8/16

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