Lab 1

Question 1

what factor are melting point, boiling point and solubility determined by

Answer 1

intermolecular forces

Question 2

how are hydrocarbons bonded

Answer 2

weakly, by London/Vander Waal forces

Question 3

what is the relationship between molecular size and molecular forces

Answer 3

as molecular size increases, molecular forces increase and you need more energy to pull the molecules apart

Question 4

what is hexane

Answer 4

a common liquid solvent because it is strong yet flexible to form a fluid

Question 5

dipole-dipole

Answer 5

• attraction increases when functional groups have atoms more electronegative then carbon
• pulls electrons and the bond becomes slightly negative, making the carbon slightly positive

Question 6

relationship between polar bonds and dipole moments

Answer 6

there is a slight charge separation, which gives a dipole

Question 7

ionic general melting point

Answer 7

usually solids with a high melting point (like table salt)

Question 8

what are the functional groups that form ionic structures

Answer 8

• hydrogen on the -OH of carboxyl group in carboxylic acids reacts with a base to form salt (reversed by adding acid to lower pH)
• hydrogen on an -OH group attached to an aromatic ring is weakly acidic and reacts with strong base to form salt (reversed by adding acid)
• amines react with acid to form ionic amine salts

Question 9

what type of thermometer is best for high temperatures

Answer 9

mercury-in-glass thermometers are highly accurate and ideal for high temps

Question 10

characteristics of a digital thermometer

Answer 10

• low heat capacity

- fast response time

Question 11

at what range of temps are non mercury thermometers best at

Answer 11

temps less then 150 degrees C

Question 12

what can melting point tell you

Answer 12

• characterization
• future characterization
• purity

Question 13

what is translational motion

Answer 13

when liquid turns to solid

Question 14

how do you find the total attractive forces when you have pure compounds with identical molecules

Answer 14

it is the sum of all of the forces

Question 15

definition of solubility

Answer 15

disrupting forces to get molecules to interact

Question 16

trends in solubility based on size of hydrocarbon

Answer 16

bigger hydro=less soluble and vice versa

Question 17

golden rule for predicting solubility

Answer 17

LIKE DISSOLVES LIKE

Question 18

what type of bond and melting temp range do most organic molecules have

Answer 18

most are covalent and melt at temps below 300 degrees C

Question 19

what type of bond and melting temp range do most inorganic molecules have

Answer 19

ionic bonds and a melting point at higher temps

Question 20

what happens to ionic organic molecules and things with strong hydrogen bonds before they melt

Answer 20

they decompose

Question 21

relationship between molecule size and melting point

Answer 21

large molecules melt at higher temperatures and vice versa

Question 22

what type of isomers will have a higher melting point

Answer 22

symmetrical isomers will have higher melting points

Question 23

what type of melting point do molecules have that can form hydrogen bonds

Answer 23

high

Question 24

relationship between vpor pressure and melting point of pure compounds

Answer 24

the melting point of a pure compound is at the temp at which the vapor pressure of the solid and liquid are equal

Question 25

what should the temp increase not be greater than per minute at the melting point

Answer 25

1 degree C per minute

be careful that the rate of heating is not too fast

Question 26

how does hydrogen bonding work

Answer 26

• between organic molecules with -OH or -NH groups
• hydrogen is attracted to unshared pair of electrons in the o or the n
• turns into molecular velcro (can be pulled apart with sufficient energy)

Question 27

when you are working with molecules of the same weight, how can you distinguish the boiling point

Answer 27

dipoles will have the second highest and hydrogen bonds will have the highest boiling point

Question 28

relationship between hydroxyl group and boiling point when you have 2 structures of the same weight

Answer 28

1 hydroxyl group will be lower bp than 2

Question 29

what is boiling point a function of

Answer 29

atmospheric pressure, because boiling point occurs when the vapor pressure is equalling the pressure exerted

Question 30

what is superheating

Answer 30

when the temp is above the boiling point but it is not boiling

Question 31

what does distillation allow us to find

Answer 31

the boiling point temperature range and also gives us an indication of purity

Question 32

how does increased surface area affect the boiling point

Answer 32

it raises it, ex) branching makes less surface area than zig zag so it has a lower boiling point because it decreased the surface area between the attractive forces