Which of the following elements would form oxides which would indicate pH values less than seven, using moist pH paper? Magnesium, Carbon, Sulphur, Hydrogen, copper

Both sulphur and carbon burn in the air to form sulphur dioxide and carbon dioxide. Both are having pH less than 7 which indicates acidic oxides.

Hydrogen will form water by reacting with oxygen and the pH will be 7 as it is neutral. Magnesium and copper does not form oxides which having less than pH 7

• The pH values of five solutions A, B, C, D and E are given below:

A B C D E

1 5 7 11 13