# How could spectrophotometry be used to determine an unknown salt?

By comparing the absorbance of an unknown sample of a salt (such as $F e C {l}_{3}$) with absorbance values for known concentrations of the same salt.

#### Explanation:

The independent variable will be plotted on the x-axis (horizontal). This is the variable that you set up (or manipulate) for the experiment.

The dependent variable goes on the y-axis (vertical) and is what you measure as you are doing the experiment.

You should list the dependent variable before the independent when using vs. to describe a graph. This is just the standard way of describing a graph...

Here is a sample of what a graph analyzing data from this type of experiment should look like.

Here is a video of a spectrophotometry experiment which shows a student setting up different concentrations of iron (III) chloride solutions and then measuring the absorbance of the samples.

Video from: Noel Pauller