问答题
Plot the melting points of NaCl, KCl, RbCl, and CsCl versus their formula weights. By extrapolation of the plot, estimate the melting point of lithium chloride. Explain why LiCl actually melts at a much lower temperature.
【正确答案】When the melting points are plotted against the formula weights, the curve extrapolates to about 840℃, 230℃ above its actual melting point. The lattice is comparatively unstable because of the very small size of the Li+ ion. The radius ratio is 0.33, below the minimum(0. 414) for the rock salt structure.