CBSE Class 10 Science 2021 Term 1 Solved Paper

Question : 2

Total: 60

Which of the following oxide(s) is/are soluble in water to form alkalies?
(i) Na2O
(ii) SO2
(iii) K2O
(iv) NO2

(i) and (iii)
(i) only
(ii) and (iv)
(iii) only

Solution:

Explanation: Most metal oxides are insoluble in water but some of these dissolve in water to form alkalis. For example, sodium oxide (Na2O) and potassium oxide (K2O) dissolve in water to produce alkalis sodium hydroxide and potassium hydroxide respectively. The reactions can be represented as follows:
Na2O( s)+H2O(l)‌→2‌NaOH(aq)
K2O( s)+H2O(l)‌→2‌KOH(aq)

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