In the structure of SF₄, the lone pair of electrons on S is in.

A student needs to prepare a buffer solution of propanoic acid and its sodium salt with pH 4. The ratio of $${{[C{H_3}C{H_2}CO{O^ - }]} \over {[C{H_3}C{H_2}COOH]}}$$ required to make buffer is ___________.

Given : $${K_a}(C{H_3}C{H_2}COOH) = 1.3 \times {10^{ - 5}}$$

Match List - I with List - II :

Choose the correct answer from the options given below :

Among the following, basic oxide is :