melting point/boiling point pre/post lab

Question 1

Which technique will you use to determine the purity of a solid sample?
mixed melting point
melting point
boiling point
mixed boiling point

Answer 1

melting point

Question 2

Which technique will you use to determine the identity of a solid sample?
mixed melting point
melting point
boiling point
mixed boiling point

Answer 2

Mixed melting point

Question 3

Will an impurity increase or decrease the melting point temperature of a pure sample?
increase
decrease

Answer 3

decrease

Question 4

Will an impurity increase or decrease the melting point range of a pure sample?
increase
decrease

Answer 4

increase

Question 5

Which technique will you use to determine the identity of a liquid sample?
mixed melting point
melting point
boiling point
mixed boiling point

Answer 5

boiling point

Question 6

What should the melting point range be for a pure substance?
3-5 degrees C
2-4 degrees C
5-10 degrees C
1-2 degrees C

Answer 6

1-2 degrees C

Question 7

In this experiment, the thermometer bulb should be positioned in the vapor and not in the liquid to determine the boiling point of your liquid.
True
false

Answer 7

true

Question 8

What is the purpose of wrapping the boiling point apparatus with aluminum foil?
to maximize heat loss
to maximize cooling
to minimize heat loss
to protect from light

Answer 8

to minimize heat loss

Question 9

Will strong IMFs result in a higher boiling point for a liquid or lower boiling point for a liquid?
higher boiling point
lower boiling point

Answer 9

higher boiling point

Question 10

Will strong IMFs result in a higher melting point for a solid or a lower melting point for a solid?
higher melting point
lower melting point

Answer 10

higher melting point

Question 11

The impure sample should at least start to melt at a much ……………………… temperature than the pure.

Which of the following fits the blank?

Answer 11

lower

Question 12

What are the two most important intermolecular forces present in your unknown solid that need to be broken in order to
melt a solid sample of it?
Ion-Dipole forces
Hydrogen bonding
London dispersion forces
Covalent bonding

benzoic acid

Answer 12

Hydrogen bonding
London dispersion forces

Question 13

What are the two most important intermolecular forces present in your unknown liquid that need to be broken in order to
boil a liquid sample of it?
Ion-Dipole forces
hydrogen bondign
London dispersion forces
Covalent bonding

ethanol

Answer 13

hydrogen bondign
London dispersion forces

Question 14

Which intermolecular force do you think is primarily responsible for the difference in boiling point between acetone and isobutane ?

Answer 14

Dipole-Dipole forces

Question 15

Which intermolecular force do you think is primarily responsible for the difference in boiling point between 1-hexanol and nonanal
a.Induced Dipole
b. Hydrogen bonding
c.London dispersion forces
d. A or C?

Answer 15

d. A or C?

Question 16

At room temperature, benzene is a liquid and naphthalene is a solid. Which intermolecular force is responsible for the higher melting point of naphthalene?
London dispersion forces
Hydrogen bonding
Dipole-Dipole forces
Ion-Dipole forces

Answer 16

London dispersion forces

Question 17

The melting point of an unknown sample (not yours) was taken and found to have a melting point range of 114 - 121°C.

What can you conclude about the purity of this sample?
a. pure
b.impure

Answer 17

impure

Question 18

The sample mentioned in the previous question is known to be one of four known chemicals.

These four known chemicals have melting points of A = 112-113°C, B = 115-116°C, C = 118-119°C and D = 121-122°C.

Which of these known chemicals, A, B, C or D is most likely to be the unknown sample from the previous question?

Hint: Pure samples have higher and narrower melting range

Answer 18

B

Question 19

Breaking the IMFs ……………….. the energies of the electrons.

Which of the following fits the blank?
a. raises
b.lowers

Answer 19

raises