Chapter 4, Problem 4.1P

(Sample Problems 4.1 and 4.2)

4.1 What two factors cause water to be polar?

Interpretation Introduction

Interpretation: Two factors that cause polarity in ${\text{H}}_2\text{O}$ should be determined.

Concept introduction: Solution is made by two portions, solute, and solvent. Solute represents substance present in small quantity while solvent represents substance that dissolves solute.

Polarity in molecule is generated if it has unequal distributed electron density between bonds. Polar molecule has partial charges on atoms of the molecule. The general representation of polar molecule is as follows:

  

Here, B has high electronegative value than A.

Explanation of Solution

Water molecule has bend shape. In this shape, oxygen present as central atom and two hydrogen atoms are present as side atom. Structure of ${\text{H}}_2\text{O}$ molecule is as follows:

  

Bond $\text{O}-\text{H}$ present in water molecule has more electronegative oxygen atom and less electronegative hydrogen atom. Therefore, oxygen atom would attract bonding electrons towards it and acquires partially negative charge. Since electrons moved away from hydrogen thus it acquires partially positive charge. This unequal distribution of bonding electrons in $\text{O}-\text{H}$ bond makes ${\text{H}}_2\text{O}$ molecule polar in nature.