What is the concentration of lithium ions in 0.400 M Li₂HPO₄?

0.800 M

Basically, the ratio is 2:1, so when you have 1 M of Li2HPO4 it means you have 2 M in the concentration of lithium ions. So knowing the ratio, we know we just need to multiply 0.400 x 2.

I'm bad at explaining it, but got it right on chem101 sooo

The best graph Rob can use to show his data is a scatter plot. A scatter plot shows a relationship between two sets of data in this case the solids and their respective solubility. A scatter plot is very specific in showing how one variable is affected by another variable.