Which of the following best specifies the purpose of error bars on a graph? to show the mean of a data set to identify the independent variable to give a visual display of measurement precision to indicate the total number of measurements that are made

to give a visual display of measurement precision

Explanation:

Error bars on graphs indicate how far the measured value is from the true value. In other words it is a measure of how precise the reported value is and gives the uncertainty of measurement.

It is depicted as a vertical line which extends above (positive direction) and below(negative) the measured value. For example in the measurement of length, if one of the reported value is 23 ± 0.1 mm then, the ± 0.1 would be the deviation (uncertainty) in the measurement.

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%