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Topic 13: Lab and measurements

Set B: Lab data, lab calculation, Percent error

1. A student determined the percentage of water of hydration in BaCl2. 2H2O by using the data in the

table below.

Quantity Measured Value Obtained
Mass of BaCl2. 2H2O 3.80 grams
Mass of BaCl2 3.20 grams
% of water calculated 15.79 %

The accepted percent of water of hydration is 14.75 %. What is the student’s percent error?

1) 1.04 % 2) 6.00 % 3) 6.59 % 4) 7.05 %
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2. A student determined in the laboratory that the percent by mass of water in CuSO4. 5H2O is 40.0%. If

the accepted value is 36%, what is the percent error?

1) 0.11 % 2) 1.1 % 3) 11 % 4) 4.0 %

3. A student calculated the percent by mass of water in a hydrate as 14.2 %. A hydrate is a compound

that contains water as part of its crystal structure. If the accepted value is 14.7 %, the student’s percent

error was

1) 0.5 ____ x 100 3) 0.5 ___ x 100

4) 14.2
2) 14.7
___ x 100
___ x 100
14.2 14.2 14.7 14.7

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4. A student found the boiling point of a liquid to be 80.4 C . If the liquid’s actual boiling point is 80.6 C ,

the experimental percent error is equal to

3) 80.5 - 80.4
_____________ x 100 ___________ x 100
1) 80.6 - 80.4
80.6 80.5

2) 80.6 - 80.4

______________ x 100 ____________ x 100
4) 80.5 - 80.4
80.4 80.4

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5. A sample of water is being heated from 20 C to 30 C, and the temperature is recorded every 2

minutes. Which table would be most appropriate recording the data?

1) 2) 3) 4)

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