Chapter 12, Problem 12.138MP

Assume that 1588 g of an alkali metal undergoes complete reaction with the amount of gaseous halogen in a 0.500 L flask at 298 and 755 mm Hg pressure. In the reaction, 22.83 kJ is released $(\Delta H=-22.83\text{ kJ)}\text{.}$ The product, a binary ionic compound, crystallizes in a unit cell with anions in a face-centered cubic arrangement and with cations centered along each edge between anions. In addition, there is a cation in the center of the cube.

1. What is the identity of the alkali metal?
2. The edge length of the unit cell is 535 pm. Find the radius of the alkali metal cation from the data Figure 6.1, and then calculate the radius of the halide anion.Identify the anion from the data in Figure 6.2.
3. Sketch a space-filling, head-on view of the unit cell, labeling the ions. Are the anions in contact with one another?
4. What is the density of the compound in g/cm³?
5. What is the standard heat of formation for the compound?