Consider the following statements: 1. Packaged foods are purged with nitrogen gas in order to prevent their oxidation. 2. Tooth decay starts when pH of the mouth is lower than 5.5. 3. The reactivity of metals decreases in the order: Mg > Fe > Zn. Which of the statements given above is/are not correct?

Statement 1 is correct: nitrogen is an inert gas used to flush packaged foods (especially chips) to prevent oxidation and rancidity. Statement 2 is correct: enamel demineralisation and tooth decay begin when oral pH drops below 5.5. Statement 3 is incorrect: according to the reactivity series, the correct order is Mg > Zn > Fe, not Mg > Fe > Zn. Hence only statement 3 is not correct.