What is the pH scale? The pH value of fresh milk is $6$. What would be the change in pH after its conversion into curd?

Which acid is present in each of the following? 

(a) Sour milk (b) Tamarind (c) Orange.

What is gypsum? What happens when gypsum is heated to $373\mathrm{K}$?

What are the common names of the following?

(a)$\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$    (b)${\mathrm{Na}}_2{\mathrm{CO}}_3.10{\mathrm{H}}_2\mathrm{O}$   (c)${\mathrm{NaHCO}}_3$.

In the given figure the experiment of conductivity solution is shown. Label against $\left[1\right],\left[2\right],\left[3\right],\left[4\right]$ and $\left[5\right]$.

What is an alkali? Do basic solutions also have ${\mathrm{H}}^{+}$(aq) ions? If yes, then why are these basic? 

Write the chemical formulae of the following:

(a) Common salt  (b) Slaked lime (c) Bleaching powder.