Add universal indicator to the beakers of water. Add a small amount of each salt to a different beaker and stir to dissolve. Compare the colors to the reference set. Note: the NaCl will not be pH 7, ...

excess base is added to the acid. The mixture can then be filtered to remove unreacted metal carbonate or metal oxide. The filtrate can then be evaporated to leave the salt produced. Watch this ...

Zinc oxide is a base, because it reacts with an acid to form a salt and water. It is not an alkali because it does not dissolve in water.