(Prelim) Exp 2&3 Post-LAB Flashcards
It is the range of temperature at which the solid phase changes to liquid.
Melting Point
It is the temperature at which the thermal motion of the molecules is just enough to break down the lattice structure of the crystal
Melting Point
have sharp melting point because of the symmetry in structure and
in strength of bonds.
Crystal solids
have sharp melting point and this physical property can be used to determine purity or presence of impurities.
Pure compounds
It provides a means of testing for the identity of two solids by examination of the melting
point behavior of a mechanical mixture of the two
Mixed melting points method
It is valuable at certain points for the identification of unknowns.
Mixed melting points method
the larger the molecule, the higher the melting point.
For alkanes
the more ordered the molecule, the more energy is required to break the intermolecular
forces holding the molecules together.
For solids
have a lower trend in melting points than even-numbered alkanes because even-
numbered pack well in the solid phase, forming a well-organized structure.
Odd number alkanes
have higher melting points compared to non-planar hydrocarbons with similar molecular weights
Flat shape aromatic compounds
In the periodic table, melting point decreases
from center going to the sides (left and right); decrease from top to bottom.
have very high melting points
Ionic compounds
Presence of polar and hydrogen-bonding groups on organic compounds generally leads to _____________
higher melting points
Oxalic acid
MW: 90
MP: 102
Naphthalene
MW:128
MP: 80.26
Benzoic acid
MW: 122
MP: 122
Malic acid
MW: 134
MP: 130
Urea
MW: 60
MP: 133
Salicylic acid
MW: 138
MP: 158.6
Succinic acid
MW: 118
MP: 184
Apparatus used to measure melting point:
- Thomas-Hoover Uni-melt melting point apparatus
- Thiele tube melting point apparatus
- Fisher-johns melting point apparatus
- Nalge-axelrod melting point apparatus
- Stuart melting point apparatus SMP10
p-amino benzoic acid
MW: 137
MP: 187
It is the temperature in which the vapor pressure is equal to the atmospheric pressure.
Boiling Point
Sodium benzoate
MW: 144
MP: 410
It can give information about their physical properties and structural characteristics of
compounds.
Boiling Point
It can also be used identify and characterize compounds.
Boiling Point
Just like melting point, the relative strength of intermolecular forces can affect ________
boiling point of compounds
It is dependent on the kinetic energy of particles and varies with the surrounding
atmospheric pressure
Boiling Point
Presence of polar and hydroxyl groups can increase ______________
boiling point of compounds.
As the length of ________ increases, the boiling point also increases
carbon chain
Increase in the length of the carbon chain increases surface area of the compound while branching of molecules __________ the surface area.
decreases
_________________ boil higher than secondary and tertiary alcohols.
Primary alcohols
Acetic acid
MW: 60
BP: 118
N-hexane
MW: 86
BP: 68.6
N-pentane
MW: 72
BP: 36.1
N-butyl alcohol
MW: 74
BP: 117.7
Sec-butyl alcohol
MW: 144
BP: 112
Tert-butyl alcohol
MW: 74
BP: 82.2
