Question

1. Without looking up the actual value, rank the following metals in order of increasing melting point.

indium, cesium

2. Calcium crystallizes in a face-centered cubic unit cell with an edge length of 558.84 pm. Calculate the density of the metal. answer in g/mL

3.What is the density of KCl at 25.00 °C if the edge length of its fcc unit cell is 628 pm? answer in g/cm3

Answer 1

1. The melting and boiling points of typical metals, as a rule, increase with a transition from bottom to top along a group of a periodic system of chemical elements. Therefore, first comes cesium, then indium.

2. We calculate the density by the formula: p = m / V

Since Calcium crystallizes in a face-centered cubic, we find the volume by the formula:

V = a3 = 558.84³ * pm = 17.4 * 10^-23cm3

4 atoms in a crystalline bond

Find the mass: 4 Ca atoms * 40.078 g / 6.022 * 10²³ atoms = 160.312g/6.022 * 10^-23 = 26.62 * 10^-23 g

p = m / V = ​​26.62 * 10^-23g /17.4 * 10^-23cm3= 1.529g/cm³ = 1.529g/ml

3.Similarly, according to formulas 2 points:

V = a3 = 628³*pm = 24.7 * 10^-23cm³

M=4*39.0983+4*35.453/6.022*10²³=49.519*10^-23

p = m / V = ​​49.519* 10^-23 g /24.7 * 10^-23cm³= 2.00g/cm3