Analytical Chemistry

Learn the toughest concepts covered in your Analytical Chemistry class with step-by-step video tutorials and practice problems.

Experimental Error

Uncertainty

Uncertainty can be thought of as the range (+/-) that is associated with any given value.

Types of Uncertainty

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concept

Types of Uncertainty

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Types of Uncertainty

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Problem

Calculate the absolute uncertainty from the given problem.

6.77 (± 5.6%) 

Propagation of Uncertainty from Random Error

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Propagation of Uncertainty

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Propagation of Uncertainty

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Propagation of Uncertainty

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Propagation of Uncertainty Calculations

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Problem

Determine the absolute and relative uncertainty to the following addition and subtraction problem.

8.88 (± 0.03) - 3.29 (± 0.10) + 6.43 (± 0.001) 

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example

Propagation of Uncertainty Calculations

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Problem

Determine the absolute and relative uncertainty to the following multiplication and division problem. 

1.12(±0.01) x 0.546 (±0.01) / 3.12(±0.02) x 1.12 (0.03)

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example

Propagation of Uncertainty Calculations

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Problem

Based on the previous example calculate the molarity value for each student if they dissolve 0.300 (± 0.03) moles of analyte. 

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example

Propagation of Uncertainty Calculations 4

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Propagation of Uncertainty Calculations 4

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Problem

I am making a 0.1 M KCl (molar mass 74.551) solution for an experiment. To measure the mass of the KCl, I will use an analytical balance that is only accurate to ± 0.01 g. I place a piece of paper on the balance and set the tare to read 0.00. I then put the KCl on the balance until it reads 6.79 g. What is the uncertainty in this mass? 

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Problem

The volume of the solution I am making is 2.5 L. To measure this volume I will use a large graduated cylinder that can measure volume to ± 10 mL. What is the absolute uncertainty in my concentration?