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

e. Two of these

Explanation:

(a)

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

Therefore,   is acidic when dissolved in water.

(b)

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

Therefore,  is acidic when dissolved in water.

(c)

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

Therefore, Na is basic when dissolved in water.

(d)

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

,

Therefore,   is basic when dissolved in water.

(e)  Two of these.

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