HKDSE Chemistry Question Review (20240607))

Question:

Explain why we should not microwave fruits and vegetables, especially when they are cooked and stored in refrigerator overnight.

Solution:

They are rich in nitrate(V) ions. Carcinogenic nitrate(III) ions will increase gradually in concentration when they are placed at room temperature prolongedly. Even putting them in refrigerator can only retard but not reduce bacterial activity cumulatively.

In addition, heating or oxidation can also promote the conversion of nitrate(V) ions to nitrate(III) ions:

2KNO3 (aq) --> 2KNO2 (aq)+ O2 (g)

I.e. As food rots,more nitrate(IIi) will result in.