Oldhatóság - 376

a, `L_(Ca(OH)_2)` = `5.47*10^(-6)` (18 °C)

L = `[Ca^(2+)]*[OH^-]^2` = `x*(2x)^2` = `4x^3`

x = `root(3)(L/4)` = `root(3)((5.47*10^(-6))/4)` = 0,0111

`[OH^-]` = 2x = `2*0.0111` = 0,0222 `(mol)/(dm^3)`

`[H^+]` = `K_v/[OH^-]` = `(0.58*10^(-14))/0.0222` = `2.61*10^(-13)`

pH = -lg`[H^+]` = -lg`2.61*10^(-12)` = 12,58

A telített `Ca(OH)_2`-oldat pH-ja 12.58.




b, `L(AgOH)` = `1.52*10^(-8)` (20 °C)

L = `[Ag^+]*[OH^-]` = `1.52*10^(-8)` = `x^2`

x = `1.233*10^(-4)` = `[OH^-]`

`[H^+]` = `(0.676*10^(-14))/[1.233*10^(-4)]` = `5.48*10^(-11)`

pH = `-lg(5.48*10^(-11)` = 10,26

A telített AgOH-oldat pH-ja 10,26.


c, `L_(Mn(OH)_2)` = `4*10^(-14)` (18 °C)

L = `[Mn^(2+)]*[OH^-]^2` = `x*(2x)^2` = `4x^3`

x = `root(3)(L/4)` = `root(3)((4*10^(-14))/4)` = `2.154*10^(-5)`

`[OH^-]` = 2x = `2*2.154*10^(-5)` = `4.308*10^(-5)` `(mol)/(dm^3)`

`[H^+]` = `K_v/[OH^-]` = `(0.58*10^(-14))/(4.308*10^(-5)` = `1.346*10^(-10)`

pH = -lg`[H^+]` = -lg`1.346*10^(-10)` = 9,87

A telített `Mn(OH)_2`-oldat pH-ja 9,87.



d, `L_(Cr(OH)_3)` = `6.7*10^(-31)` (25 °C)

L = `[Cr^(3+)]*[OH^-]^3` = `x*(3x)^3` = `27x^4`

x = `root(4)(L/27)` = `root(4)((6.7*10^(-31))/27)` = `1,255*10^(-8)`

`[OH^-]` = 3x = `3*1.255*10^(-8)` = `3.765*10^(-8)` `(mol)/(dm^3)`

`[H^+]` = `K_v/[OH^-]` = `(1.008*10^(-14))/(3.765*10^(-8)` = `2.677*10^(-7)`

pH = -lg`[H^+]` = -lg`2.677*10^(-7)` = 6,57

A telített `Cr(OH)_3`-oldat pH-ja 6,57.


e, `L_(Fe(OH)_3)` = `3.8*10^(-38)` (18 °C)

L = `[Fe^(3+)]*[OH^-]^3` = `x*(3x)^3` = `27x^4`

x = `root(4)(L/27)` = `root(4)((3.8*10^(-38))/27)` = `1,937*10^(-10)`

`[OH^-]` = 3x = `3*1.937*10^(-10)` = `5.81*10^(-10)` `(mol)/(dm^3)`

`[H^+]` = `K_v/[OH^-]` = `(0.588*10^(-14))/(5.81*10^(-10)` = `9.98*10^(-6)`

pH = -lg`[H^+]` = -lg`9.98*10^(-6)` = 5,00

A telített `Fe(OH)_3`-oldat pH-ja 5,00.