Question

✪ Chemistry ✪
1 litre of $\sf 10^{-4} m \ Ca(No_3)_2$ is mixed with $\sf 10^{-4} m$ Naf. Predict whether precipitation will occur or not. $\sf [K_{Sp}(CaF_2) \ = \ 1.1 \times 10^{-12}]$​

Answer 1

★Given:-

• 1 litre of 10⁻⁴m Ca(NO₃)₂ is mixed with 10^-4m NaF.
• Ksp(CaF₂) = 1.1×10⁻¹²

★To find:-

• Whether the precipitation occurs or not.

★Solution:-

We know,

For a reaction like:

➜MA(s) ⇌  M⁺(aq) + A⁻(aq)

◖Ksp = [M⁺(aq)][A⁻(aq)]  

Where,

✦ Ksp is the solubility product and an equilibrium constant for a solid substance dissolving in an aqueous solution.

The ion product will be:

➜[M⁺(aq)][A⁻(aq)]    

When two solutions are mixed,the precipitate is formed if the ion product is greater than the solubility product.That is,

✦Ionic product > Ksp

➜[M⁺(aq)][A⁻(aq)] > Ksp

According to the question,

For precipitation to occur, ionic product of CaF₂ should be greater than Ksp.

i.e., [Ca⁺²][F⁻]² > Ksp

Ionic product:-

➜ Ca × F²

➜ 10⁻⁴× (10⁻⁴)²

➜ 10⁻¹²  

We have,

• Ksp = 1.1×10⁻¹²
• Ionic product = 10⁻¹²  

And we can see,

➜1.1×10⁻¹² > 10⁻¹²

➜ Ksp > Ionic product

Hence,

The precipitation doesnt occur.

______________

Extra information:-

When two aqueous solutions are mixed,

If Ionic product < Ksp :

• The solution is unsaturated
• No precipitation

If Ionic product = Ksp:

• The solution is saturated
• Equilibrium.

If ionic product > Ksp

• The solution is supersaturated
• Ionic solid will precipitate.

______________

Answer 2

Given:-

1 litre of 10⁻⁴m Ca(NO₃)₂ is mixed with 10^-4m NaF.

Ksp(CaF₂) = 1.1×10⁻¹²

To find:-

Whether the precipitation occurs or not.

★Solution:-

We know,

For a reaction like:

MA(s) ⇌  M⁺(aq) + A⁻(aq)

◖Ksp = [M⁺(aq)][A⁻(aq)]  

Where,

Ksp is the solubility product and an equilibrium constant for a solid substance dissolving in an

aqueous solution.

The ion product will be:

[M⁺(aq)][A⁻(aq)]    

When two solutions are mixed,the precipitate is formed if the ion product is greater than the

solubility product.That is,

Ionic product > Ksp

[M⁺(aq)][A⁻(aq)] > Ksp

According to the question,

For precipitation to occur, ionic product of CaF₂

should be greater than Ksp.

i.e., [Ca⁺²][F⁻]² > Ksp

Ionic product:-

Ca × F²

10⁻⁴× (10⁻⁴)²

10⁻¹²  

We have,

Ksp = 1.1×10⁻¹²

Ionic product = 10⁻¹²  

And we can see,

1.1×10⁻¹² > 10⁻¹²

Ksp > Ionic product