Question

Which of the following species act as bronsted base but not as acid?
1)cH3cooH 2)Hco3- 3)H2po2- 4)H2po3-

Answer 1

The species that act as bronsted base but not as acid is $H_2PO_2^-$

Explanation:

• According to the Bronsted-Lowry conjugate acid-base theory, an acid is defined as a substance which looses donates protons and thus forming conjugate base and a base is defined as a substance which accepts protons and thus forming conjugate acid.
• For the given chemical equation:

$CH_3COOH\rightarrow CH_3COO^-+H^+$

Here, $CH_3COOH$ is loosing a proton, thus it is considered as a bronsted acid.

• $HCO_3^-\rightarrow CO_3^{2-}+H^+$

Here, $HCO_3^-$ is loosing a proton, thus it is considered as a bronsted acid.

$HCO_3^-+H^+\rightarrow H_2CO_3$

Here, $HCO_3^-$ is gaining a proton, thus it is considered as a bronsted base.

• $H_2PO_2^-+H^+\rightarrow H_3PO_2$

Here, $H_2PO_2^-$ is gaining a proton, thus it is considered as a bronsted base. It cannot donate $H^+$ as only one hydrogen is ionizable. Thus $H_2PO_2^-$ act as bronsted base.

• $H_2PO_3^-\rightarrow HPO_3^{2-}+H^+$

Here, $H_2PO_3^-$ is loosing a proton, thus it is considered as a bronsted acid.

$H_2PO_3^-+H^+\rightarrow H_3PO_3$

Here, $H_2PO_3^-$ is gaining a proton, thus it is considered as a bronsted base.

Learn More

Bronsted acid and base:

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