Predicting changes in pH of water when chlorinating using two different methods
In aqueous solution, chlorine can undergo disproportionation: one atom in $\ce{Cl2}$ (oxidation state $0$) is reduced to $\ce{Cl-}$ (oxidation state $-1),$ the other is oxidized to a species in which the chlorine atom has the oxidation state $+1.$

$$\ce{Cl2 + 3H2O -&gt; 2H3O+ + Cl- + OCl-}$$

Ask yourself how that influences the pH of the solution.

What about adding calcium hypochlorite to water? If $\ce{CaCl2}$ is the calcium salt of hydrochloric acid, what about $\ce{Ca(OCl)2}?$

 You may have guessed it: $\ce{Ca(OCl)2}$ is the calcium salt of chloric(I) acid.

You may remember that adding the soluble salt $\ce{MA}$ of a strong acid $\ce{HA}$ to water will not influence the pH of the solution.

 If $\ce{HA}$ is a strong acid, it will fully dissociate in water:
 $$\ce{HA + H2O &lt;=&gt;&gt; A- + H3O+}$$
 This means in return that the corresponding base $\ce{A-}$ is very weak:
 $$\ce{A- + H2O &lt;&lt;=&gt; HA +OH-}$$

Now, is $\ce{OCl-}$ a strong or a weak base? In order to decide, you might want to have a look up the $\mathrm{p}K_\mathrm{a}$ of the corresponding acid and keep in mind that for a corresponding acid-base pair in water $\mathrm{p}K_\mathrm{a} + \mathrm{p}K_\mathrm{b} = 14.$