Na2CO3. AgNO3 0.839 g Pb(NO3)2 1.024 g 492 mL

Na2CO3. AgNO3 0.839 g Pb(NO3)2 1.024 g 492 mL

 

 

A solution is made by adding

0.839 g of silver(I) nitrate (AgNO3: 169.87 g/mol) and

1.024 g of lead(II) nitrate (Pb(NO3)2: 331.21 g/mol)

to enough water to make 492 mL of solution.

Solid sodium carbonate (Na2CO3) is added

without changing the volume of the solution.

 

a) What minimum concentration of CO3^2- is required

for Ag2CO3 to start precipitating?

b) What minimum concentration of CO3^2- is required

for PbCO3 to start precipitating?

c) Which will precipitate first, Ag2CO3 or PbCO3?

 

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

 

> 몰농도 = 용질 mol수 / 용액 L수

> mol수 = 질량(g) / 몰질량(g/mol)

( 참고 https://ywpop.tistory.com/7738 )

 

 

 

> AgNO3의 몰질량 = 169.87 g/mol

 

[AgNO3] = [0.839 g / (169.87 g/mol)] / 0.492 L

= 0.01004 mol/L

= 0.01004 M = [Ag^+]

 

 

 

> Pb(NO3)2의 몰질량 = 331.21 g/mol

 

[Pb(NO3)2] = (1.024 / 331.21) / 0.492

= 0.006284 M = [Pb^2+]

 

 

 

> Ag2CO3의 Ksp = 8.46×10^(-12)

> PbCO3의 Ksp = 7.40×10^(-14)

( 참고 https://ywpop.tistory.com/9909 )

 

 

 

 

a) What minimum concentration of CO3^2- is required

for Ag2CO3 to start precipitating?

 

Ag2CO3(s) ⇌ 2Ag^+(aq) + CO3^2-(aq)

Ksp = [Ag^+]^2 [CO3^2-]

 

[CO3^2-] = Ksp / [Ag^+]^2

= (8.46×10^(-12)) / (0.01004)^2

= 8.39×10^(-8) M

 

 

 

 

b) What minimum concentration of CO3^2- is required

for PbCO3 to start precipitating?

 

PbCO3(s) ⇌ Pb^2+(aq) + CO3^2-(aq)

Ksp = [Pb^2+] [CO3^2-]

 

[CO3^2-] = Ksp / [Pb^2+]

= (7.40×10^(-14)) / (0.006284)

= 1.18×10^(-11) M

 

 

 

 

c) Which will precipitate first, Ag2CO3 or PbCO3?

 

침전에 필요한 [CO3^2-] 값이 더 작은 것은?

---> PbCO3.

 

 

 

 

[키워드] 난용성염의 선택적 침전 기준문서