Melting and Boiling Points QuestionsChemistry2 points (1 for questions, 1 for graph)

Answer the questions on a sheet of lined paper. When you are done, staple your graph paper to your linedpaper and turn them both in.

1. Make a line graph of the following Group 16 data (Boiling Point vs. Period):- use graph paper to make a horizontal graph as big as the paper (no tiny graphs!)- connect the compounds from each group of data with a separate linex-axis: Period (from 1 to 6) y-axis: Boiling Point (from -100 °C to +120 °C)

Group Period Compound Molar Mass (g) Boiling Point (°C)

16

2 H2O 18 100

3 H2S 34 -60

4 H2Se 81 -41

5 H2Te 129 -2

2. Now add the Group 17 data below to the graph, connecting these new points with a different line:

Group Period Compound Molar Mass (g) Boiling Point (°C)

17

2 HF 20 19

3 HCl 36 -85

4 HBr 81 -67

5 HI 128 -35

3. Are these chemicals in the two charts polar or nonpolar? Explain your answer.4. What is the relationship between period and boiling point? (direct/indirect) Explain.5. Which molecules do not follow this relationship?6. What is different about these molecules that they don’t follow the same relationship?

(Hint: Think intermolecular forces!)7. Looking at the data, what is the relationship between boiling point and molar mass?

8. Read the following chart and answer the questions below:

Substance Molar Mass (g) Melting Point (°C) Boiling Point (°C)

F2 38 -220 -188

Cl2 71 -101 -35

Br2 160 -7 59

I2 254 114 184

(a) What periodic family do F2, Cl2, Br2, and I2 belong to?(b) What is the relationship between molar mass and boiling point within a family?(c) What type of intramolecular bonds are within an F2 molecule?(d) What type of intermolecular forces are between F2 molecules?(e) Melting is the change from _____ to _____. Boiling is the change from _____ to _____.(f) Room temperature is 25 °C. Which of the substances in the table above would be solids at

room temperature? How can you tell?

(g) Which of the substances in the table above would be liquids at room temperature?

9. Read the following chart and answer the questions below:

Chemical Formula Molar Mass (g) Boiling Point (°C)

methane CH4 16 -162

ethane C2H6 30 -89

propane C3H8 44 -42

butane C4H10 131 0

(a) What type of intramolecular bonds do these compounds have?(b) What intermolecular forces hold these chemicals together?(c) What is the relationship between number of carbons and molar mass?(d) What is the relationship between molar mass and boiling point?

10. Read the following chart and answer the questions below:

Chemical Formula Molar Mass (g) Boiling Point (°C)

acetone CH3COCH3 58 56

ethyl alcohol C2H5OH 46 78

hexane C6H14 86 68

methyl alcohol CH3OH 32 65

2-propyl alcohol C3H7OH 60 83

water H2O 18 100

(a) Which chemicals have the lowest and highest boiling points?(b) List if each chemical is polar or nonpolar. (See lab handout for structures.)(c) List the type of intermolecular forces holding each chemical together.(d) Which chemical should have evaporated the fastest during lab?(e) Which chemical should have evaporated the slowest during lab?(f) With the alcohols, what is the relationship between number of carbons and molar mass?(g) With the alcohols, what is the relationship between molar mass and boiling point?

11. Use the following chart to answer the questions below:

Substance IntermolecularForce

Melting Point(°C)

Substance IntermolecularForce

Melting Point(°C)

MgF2 ionic bond 1248 HBr dipole-dipole -89

KF ionic bond 860 HCl dipole-dipole -115

NaCl ionic bond 801 C5H12 dispersion -130

H2O hydrogen bond 0 CH4 dispersion -182

NH3 hydrogen bond - 78 H2 dispersion -259

HF hydrogen bond - 83 He dispersion -269

(a) Which intermolecular force appears to be the hardest to overcome with heat? Why?(b) Which intermolecular force appears to be the easiest to overcome with heat? Why?(c) Write a list of intermolecular forces from strongest to weakest.