Why are there trees on the roof of the white house?

There may be several reasons why there are trees on the roof of the White House. First that comes to mind is for aesthetic reasons - they make the roof seem more beautiful and appealing. Other than that, the reason may be practical - to hide the windows of the White House, so that no one can see what's happening there.

The unit cell edge length for the alloy is 0.405 nm

Explanation:

Given;

concentration of Ag, = 78 wt%

concentration of Pd, = 22 wt%

density of Ag = 10.49 g/cm³

density of Pd = 12.02 g/cm³

atomic weight of Ag, = 107.87 g/mol

atomic weight of iron, = 106.4 g/mol

Step 1: determine the average density of the alloy

Step 2: determine the average atomic weight of the alloy

Step 3: determine unit cell volume

for a FCC crystal structure, there are 4 atoms per unit cell; n = 4

Step 4: determine the unit cell edge length

Vc = a³

= 0.405 nm

Therefore, the unit cell edge length for the alloy is 0.405 nm