산-염기 적정으로 silicon tetrachloride의 순도 결정

산-염기 적정으로 silicon tetrachloride의 순도 결정

 

 

When silicon tetrachloride is added to water, the following reaction occurs:

SiCl4(l) + 2H2O(l) → SiO2(s) + 4HCl(aq)

1.2 g of impure silicon tetrachloride was dissolved in excess water, and the resulting solution was made up to 250 cm3. A 25 cm3 portion of the solution was then titrated against 0.10 moldm-3 sodium hydroxide, and 18.7 cm3 of the alkali were required. What was the percentage purity of the silicon tetrachloride?

 

-----------------------------------------

 

반응 결과 생성된 HCl의 몰농도를 계산하면,

MV = M’V’ ( 적정 시 설명 http://ywpop.tistory.com/4689 )

? M * 25 mL = 0.10 M * 18.7 mL

? = 0.10 * 18.7 / 25 = 0.0748 M HCl

 

HCl의 몰수를 계산하면,

(0.0748 mol/L) * 0.250 L = 0.0187 mol HCl

( 계산 설명 http://ywpop.tistory.com/7787 )

 

SiCl4 + 2H2O → SiO2 + 4HCl

SiCl4 : HCl = 1 : 4 계수비(몰수비) 이므로,

0.0187 mol HCl 생성될 때 반응한 SiCl4의 몰수를 계산하면,

SiCl4 : HCl = 1 : 4 = ? mol : 0.0187 mol

( 즉, 1 mol SiCl4가 반응하면, 4 mol HCl이 생성된다.
? mol SiCl4가 반응하면, 0.0187 mol HCl이 생성될까? )

? = 0.0187 / 4 = 0.004675 mol SiCl4

 

SiCl4의 몰질량 = 169.90 g/mol 이므로,

0.004675 mol SiCl4의 질량을 계산하면,

0.004675 mol * (169.90 g/mol) = 0.7943 g

 

silicon tetrachloride의 순도를 계산하면,

(0.7943 g / 1.2 g) * 100 = 66.19%

 

 

답: 66.2%