Cloth can be waterproffed by coating it with silicone layer. This is done by exp

Question

Cloth can be waterproffed by coating it with silicone layer. This is done by exposing the cloth to (CH_3)_2 SiCl_2 vapor. The silicon compund reacts with OH groups on the cloth to form a waterproofing film (density = 1.0 g/cm^3) of [(CH_3)_2 SiO]_n, where n is a larger integer number. n(CH_3)_2 SiCl_2 + 2n OH^- rightarrow 2n Cl^- + n H_2O + [(CH_3))2 SiO]_n The coating is added layer by layer, with each layer of [(CH_3)_2SiO]_n being 0.60 nm thick. Suppose you want to waterproof a piece of cloth that is 3.00 square meters, and you want 250 layers of waterproofing compound on the cloth. What mass of (CH_3)_2SiCl_2 do you need?

Explanation / Answer

ANSWER

CONCEPT: Calculate the total volume of coat. From the total volume we can calculate the total mass from the given density value.

Each coat is 0.6 nm thick

250 coats will be 0.6 X 250 = 150 nm Thick

150 nm = 150 X 10-7 cm

Volume = Surface area of the coat X thickness of the coat

Surface area of the coat = 3.0 m2 = 300 cm2.

Volume = 300 cm2 X 150 X 10-7 cm = 4.5 X 10-3 cm3

Density = 1g/cm-3

It means mass of one cm-3 = 1g

So mass of 4.5 X 10-3 = 4.5 X 10-3 g = 4.5mg

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