(a) Confirm that lattice energies are inversely proportional to the distance between the centers of the ions in MX (M = alkali metal, X = halide ion) by plotting the lattice energies of KF, KCl, and KI against the internuclear distances d_{M - X}. The lattice energies of KF, KCl, and KI are 826, 717, and 645 kJ ? mol ^-1, respectively.

How good is the correlation? You should use a standard graphing program (for instance, with a spreadsheet program) to make the plot that will generate an equation for the line and calculate a correlation coefficient for the fit.

(b) Estimate the lattice energy of KBr from your graph.

(c) Find an experimental value for the lattice energy of KBr in the chemical literature and compare that value with the value that you calculated in part (b). How well do they agree?