experiment 1: identify a compound by its melting point and ... a acetic acid - water solution with a...
TRANSCRIPT
Melting Points and Mixed Melting PointsExperiment 1: Identify a compound by its meltingpoint and mixed melting points.
Acetamide
p-Aminobenzoic acid
Camphoric Acid
trans-Cinnamic Acid
Malonic Acid
p-Nitrophenol
Resorcinol
Succinic Acid
Urea
113 - 115 oC
188 - 189 oC
183 - 186 oC
133 - 134 oC
135 - 137 oC
113 - 115 oC
110 - 113 oC
187 - 189 oC
133 - 135 oC
Put a small amount of the compound in theopen end of the melting point tube.
Turn over and tape the closed end on the desktop until the compound falls to the bottom.
Heat about 5o per minuteuntil within about 10o ofthe melting point
Near the melting pointheat at 1 - 2o perminute
Impurities such as salt lowers the meltingpoint of water.
Putting salt on icy roads causes the ice tomelt because it lowers the melting point ofwater.
Impure compounds usually melt lower thanpure compounds so the melting point maybe used as a measure of the purity of acompound
Acetic Acid, CH3COOH,is a colorless liquid thatmelts at 16.6oC.
Let’s look at the melting point ofmixtures of water and acetic acid.
Pure compounds usually melt overa narrow temperature range, often1o or less.
Impure compounds melt lowerthan pure compounds and over awider temperature range.
m.p. = 120o - 122o m.p. = 120o - 122o m.p. = 120o - 122o
Two of these bottles contain benzoicacid and one m-nitrophenylacetic acid.
How do you tell what is in each bottle?
Mixed Melting Points
Grind samples together to be sure they aremixed and then measure the melting point.
m.p. = 114o - 117o
m.p. = 120o - 122o
m.p. = 115o - 118o
Mixed 1 and 2
Mixed 1 and 3
Mixed 2 and 3
1 2 3
Results