Percent Error

Relative Error is expressed as a percentage and essentially tells us how far our

measured value is from a true value. It is calculated by taking the absolute value

of the difference between a measured value and a true value. If we measure the

density of an aluminum bar to be 2.63 g/mL, but the true density of aluminum is

2.70 g/mL then our Relative Error is 3%:

Pre-Lab Questions

1. What are the safety considerations for using a Bunsen burner?

2. In the SDS sheets for SiO₂, NaCl, and C₆H₅COOH, what are the main hazards

associated with these substances? What precautions do you think should be

taken when working with these substances?

3. Look at the different steps of the experiment. In what phase is each of the

three different components at each step of the procedure? In step 2 of the

experiment, what type of mixture will you have before decanting and after

decanting?

4. Think about the masses you will need to take during the experiment. Set-up a

table for recording data in your laboratory notebook where you will record all

those masses. Think about whether you will be measuring directly or

measuring by difference for each of the components. If measuring by

difference, between what masses will you be taking the difference?

5. What physical property of the mixture components are you using to separate

them? What are the laboratory techniques used to separate each of the

different components from the various mixtures?

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