We learned salts come from acids and bases, but some salt solutions turn litmus red and some blue. How do I predict whether a given salt is acidic or basic?
Look at the strengths of the parent acid and base that formed the salt. A salt of a strong acid and a strong base, like sodium chloride (from HCl and NaOH), is neutral, so it does not change litmus and has a pH near 7. A salt of a strong acid and a weak base, like ammonium chloride (from HCl and NH4OH), is acidic and turns blue litmus red, because the weak base part undergoes hydrolysis releasing H+ ions. A salt of a weak acid and a strong base, like sodium carbonate (from H2CO3 and NaOH), is basic and turns red litmus blue. The rule of thumb: the stronger parent wins and decides the nature. Identify the acid and base that made the salt, compare their strengths, and you can predict the result.
Sign in as a tutor to answer this doubt.