Evidence table approach

List whether the oxide reacts with acid and whether it reacts with alkali. Reaction with acid only suggests basic; with alkali only suggests acidic; with both suggests amphoteric. No observed reaction may require stronger conditions or may indicate an oxide outside the listed classes.

Using periodic position

Metal oxides are generally basic and non-metal oxides generally acidic. Elements near the metallic/non-metallic boundary may form amphoteric oxides. This is a prediction, not a replacement for experimental evidence.

Equation reasoning

Products should normally be salt and water. Balance equations and check the salt name from the acid. If sodium hydroxide is used with an amphoteric oxide, product naming or formula may be provided.

Data questions

A question may give pH of oxide-water mixtures, reaction observations and element position. Combine all evidence. Some oxides do not dissolve in water but still react with acid or base, so water pH alone is incomplete.

Review questions and suggested answers