Common ion effect and Buffer sol

Which of the following will show common ion effect and form a buffer solution?

Assertion : I_2 is less soluble in Kl(aq) than in pure water Reason : Common ion effect reduces the solubility.

Weak and strong electrolytes || Ionisation constant OF weak and strong electrolyte || Common ion effect and its application

Solubility and solubility product | Common ion effect on solubility | Simultaneous solubility | Precipitation reactions

Statement: In acidic medium, Zn^(2+) is not precipitated by H_(2)S . Explanation: Common ion effect reduces the concentration of S^(2-) to a minimum level.

While calculate the pH of 10^(-7)M HCI , the common ion effect of HCI on water is considered. Why the common ion effect of water on HCI is not considered?

Assertion : On passing HCl(g) through a saturted solution of BaCl_(2) , a white turbidity appears. Reason : The common ion effect is responsible for white turbidity.