JEE Main2012ChemistryIonic EquilibriumActual
If K_ s p of CaF ₂ at 25^ C is 1.7 10⁻¹⁰ , the combination amongst the following which gives a precipitate of CaF ₂ is
Options
- A1 10⁻² M Ca ²⁺ and 1 10⁻³ M F ⁻
- B1 10⁻⁴ M Ca ²⁺ and 1 10⁻⁴ M F ⁻
- C1 10⁻² M Ca ²⁺ and 1 10⁻⁵ M F ⁻
- D1 10⁻³ M Ca ²⁺ and 1 10⁻⁵ M F ⁻
Correct answer
A. 1 10⁻² M Ca ²⁺ and 1 10⁻³ M F ⁻
Step-by-step solution
When ionic product i.e. the product of the concentration of ions in the solution exceeds the value of solubility product, formation of precitpiate occurs. aligned & CaF ₂ Ca ²⁺+2 ~F ⁻ & Ionic product = [ Ca ²⁺ ] [ F ⁻ ]^2 & when, [ Ca ²⁺ ]=1 10⁻² M & [ F ⁻ ]^2= (1 10⁻³ )^2 M & =1 10⁻⁶ M & [ Ca ²⁺ ] [ F ⁻ ]^2= (1 10⁻² ) (1 10⁻⁶ )=1 10⁻⁸ & In this case, & Ionic product (1 10⁻⁸ )> & solubility product (1.7 10⁻¹⁰ ) aligned Hence (a) is correct option.