Answer to Question #271927 in General Chemistry for leo

Question

The reaction of liquid silicon tetrachloride and magnesium forming silicon and  magnesium chloride. This is one step in the preparation of ultrapure silicon used  in the semiconductor industry.

Answer 1

(a)

SiCl4 (s) + 2 Mg (s) -----------> Si (s) + 2 MgCl2 (s)

(b)

Mass of Si = 0.130 kg = 130 g.

Molar mass of Si = 28.1 g/mol

Moles of Si = mass / molar mass = 130 / 28.1 = 4.63 mol

From the balanced equation,

1 mol o fSi is obtained from 1 mol of SiCl4

Then, 4.63 mol of Si is obtained from 4.63 mol of SiCl4

Mass of SiCl4 = moles * molar mass = 4.63 * 170.1 = 788 g. = 0.788 kg. of SiCl4 is need.

From the balanced equation,

1 mol of Si is obtained from 2 mol of Mg

Then,

4.63 mol of Si is obtained from 4.63 * 2 = 9.26 mol of Mg

Mass of Mg = 9.26 * 24 = 222. g. = 0.222 kg. of Mg is neded.

(c)

Since actual yield is 93.0 %,

Mass of SiCl4 = 0.788 * 100 / 93 = 0.847 kg.

Mass of Mg = 0.222 * 100 / 93 = 0.239 kg.