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Question
Which of the following elements would from oxides which would indicate pH values less than seven, using moist pH paper?
Magnesium, Carbon, Sulphur, Hydrogen, Copper
Solution
Sulphur and Carbon burn in the air to form sulphur dioxide and carbon dioxide. Both are acidic oxides that indicate pH values less than 7 when moist pH paper is used.
S + O2 → SO2
C + O2 → CO2
Hydrogen is also a non-metal, but forms water, which has a neutral pH of 7, after reacting with oxygen. The oxides of magnesium and copper do not have pH values less than 7.
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