Polarity Worksheet



Polarity Of Molecules

For each of the following pairs of molecules, determine which is most polar and explain your reason for making this choice:

1) carbon disulfide OR sulfur difluoride

2) nitrogen trichloride OR oxygen dichloride

3) boron trihydride OR ammonia

4) chlorine OR phosphorus trichloride

5) silicon dioxide OR carbon dioxide

6) methane OR CH2Cl2

7) silicon tetrabromide OR HCN

8) nitrogen trifluoride OR phosphorus trifluoride

Types of Intermolecular Forces

What is the strongest intermolecular force present for each of the following compounds?

1) water _____________________________________

2) carbon tetrachloride _____________________________________

3) ammonia (NH3)_____________________________________

4) carbon dioxide _____________________________________

5) phosphorus trichloride _____________________________________

6) nitrogen _____________________________________

7) dihydrogen Sulfide _____________________________________

8) methane (CH4) _____________________________________

9) pure copper _____________________________________

10) Sodium Chloride _____________________________________

11)

Substance Melting Point, °K Substance Melting Point, °K

N2 63.3 Kl 854.15

C2H6 89.85 NaF 1266.15

HCl 158.4 Cu metal 1357

In terms of the types of intermolecular forces in the above substances, explain the trend

in the melting points.

12) Which are stronger intermolecular forces or the bonds that hold atoms together in the molecules? Explain your reasoning using evidence from the behavior of a common substance like water.

13) Water will dissolve ionic and polar solutes but not non-polar solutes. Describe how the polar nature of water molecules causes this.

Polarity Worksheet Answers

For each of the following pairs of molecules, determine which is most polar and explain your reason for making this choice:

1) carbon disulfide OR sulfur difluoride

carbon disulfide is nonpolar

2) nitrogen trichloride OR oxygen dichloride

both are polar, but oxygen dichloride is less symmetric than nitrogen trichloride, making it more polar.

3) boron trihydride OR ammonia

boron trihydride is nonpolar.

4) chlorine OR phosphorus trichloride

chlorine is nonpolar

5) silicon dioxide OR carbon dioxide

It’s a tie, because both are nonpolar

6) methane OR CH2Cl2

methane is nonpolar

7) silicon tetrabromide OR HCN

silicon tetrabromide is nonpolar

8) nitrogen trifluoride OR phosphorus trifluoride

Both are polar and equally symmetric, but the difference in electronegativity between N-F is less than that between P-F

Types of Intermolecular Forces - Solutions

What is the strongest intermolecular force present for each of the following compounds?

1) water hydrogen bonding

2) carbon tetrachloride London dispersion forces

3) ammonia hydrogen bonding

4) carbon dioxide London dispersion forces

5) phosphorus trichloride dipole-dipole forces

6) nitrogen London dispersion forces

7) dihydrogen Sulfide dipole-dipole forces

8) methane (CH4) London dispersion forces

9) pure copper metallic

10) sodium chloride ionic

11) N2 and C2H6 are both non-polar and the molecules of each will be attracted by relatively weak London Dispersion forces. This causes the low melting points, since C2H6 is a larger molecule the London forces will be larger than for N2 making its melting point a bit higher. HCl and KI are both polar and attracted by dipole-dipole forces which are stronger than London forces making their melting points higher. KI is more polar than HCL. NaF is attracted by ionic forces that are stronger than dipole-dipole. Cu is a pure metal forming a lattice of Cu ions in a “sea of electrons”, this is a very strong attraction and results in very high melting points.

12) Bonds between atoms a much stronger than intermolecular forces. This is evidenced by the melting and evaporating of water. The attraction between the molecules changes or breaks much more easily causing phase changes by leaving the water molecule intact.

13) Water is polar and is capable of attracting other polar molecules. Therefore, when polar or ionic compound are put in water the water molecules can pull them apart (dissolve) them by dipole-dipole forces. If the substance in non-polar than there is no attraction to the polar water molecules and the substance stay intact and separate.

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