Question

Which of the following is acidic when dissolved in water? a. SO b. NO2 c. Na, d. Cao e. Two of these modern periodic table are arranged according to increase -- and group 7A elements of periodical

Answer 1

Answer: e. Two of these

Explanation:

(a) $SO_2$

When $SO_2$ is dissolved in water. It reacts to form sulfurous acid.  The chemical reaction is shown below:

$SO_2+H_2O\rightarrow H2SO_3$

Therefore,  $SO_2$ is acidic when dissolved in water.

(b) $NO_2$

When $NO_2$ is dissolved in water. It reacts to form nitric acid.  The chemical reaction is shown below:

$3NO_2+H_2O\rightarrow 2HNO_3+NO$

Therefore, $NO_2$  is acidic when dissolved in water.

(c) $Na$

Sodium is a metal. It gives sodium hydroxide on reaction with water. The chemical reaction is as follows:

$Na+H_2O\rightarrow NaOH +H_2$

Therefore, Na is basic when dissolved in water.

(d) $CaO$

Calcium oxide is a metallic salt. It gives calcium hydroxide on reaction with water. The chemical reaction is as follows:

$CaO+H_2O\rightarrow Ca(OH)_2$,

Therefore,  $CaO$ is basic when dissolved in water.

(e)  Two of these.

Since both $SO_2$ and  $NO_2$  give acids when dissolved in water, both are acidic.