McMurry (Kap 2,2)

Question 1

Just as individual bonds can be polar, molecules as a whole can be polar also. How? and what is it called?

Answer 1

The vector summation of all the individual covalent bond polarities and lone pair contributions in a molecule result in molecular polarity.

The net molecular polarity is measured by a quantity called dipole moment (D)

Question 2

Is polar or non-polar substances soluble in water?

Answer 2

Polar substances are soluble in water.

Less polar substances are insoluble in water.

“like attract like”

Question 3

What to know about the dipole moment?

Answer 3

The dipole moment can be found if you know the charge at either ends of the molecular dipole, and the distance between the charge (formel s.31)

• The longer the distance between the positive and negative charge (the greater the dipole moment)
• The bigger the charge difference between the atoms (the greater the dipole moment).

Question 4

Does ionic molecules have bigger dipole moment then polar covalent molecule?

Answer 4

Yes, because the charge is much greater (the EN difference it very high).

Question 5

Do lone pairs contribute to the dipole moment?

Answer 5

Yes, they contribute to the charge distribution.

The more the lone pairs, the greater the dipole moment

(taken into consideration that the molecule is not symmetrical, because then the bond polarities and lone pair contributions will exactly cancel out each other).