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Question
The elements whose oxides can turn litmus solution red are ______.
Options
lithium and sodium
copper and potassium
carbon and hydrogen
phosphorus and sulphur
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Solution
The elements whose oxides can turn litmus solution red are phosphorus and sulphur.
Explanation:
Litmus solution turns red in the presence of an acid. Phosphorus and sulphur are non-metals that form non-metallic oxides (P4O10 and SO2), which dissolve in water to produce strong acidic solutions (phosphoric and sulphurous acids). Conversely, metals such as lithium, sodium, copper, and potassium form basic oxides, whereas hydrogen forms water (H2O), which is neutral.
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