Carbon dioxide is a/an_____oxide.

Options

A. neutral
B. basic
C. acidic
D. amphoteric

Answer

C

Explanation

Unlike `CO, CO_(2)` is an acidic oxide. It is the acid anhydride of carbonic acid. Because it is an acid oxide, `CO_(2)` reacts with bases to give carbonates:
`2KOH(aq.) + CO_(2)(g) rarr K_(2)CO_(3)(aq.) + H_(2)O(l)`
`Ca(OH)_(2)(aq.) + CO_(2)(g) rarr CaCO_(3)(s) + H_(2)O(l)`
The presence of excess `CO_(2)` results in the formation of hydrogen carbonates of the alkali and alkaline earth elements:
`K_(2)CO_(3)(aq.) + CO_(2)(g) rarr 2KHCO_(3)(aq.) + H_(2)O(l)`
`CaCO_(3)(s) + H_(2)O(l) + CO_(2)(g) rarr Ca(HCO_(3))_(2)(aq.)`
The second reaction just above accounts for the formation of temporarily hard water.