Kati
B2.Density and C.3 Melting Point Determinations

Experiment B2 Purpose: Finding the density of an unknown liquid to determine its identity.

Data and Observations: Organic Compound
Density (g/ml)
Hexane
0.6603
3-methylpentane
0.6645
Heptane
0.6837
Cyclohexane
0.7785
1-propanol
0.8035
3-pentanone
0.8138 p-xylene 0.8611
Toluene
0.8669
Tetrahydroforan
0.8892
Ethyl acetate
0.9003

Technique Trial with Acetone:

Trial 1
Trial 2
Mass of empty, capped vial
7.6705g
7.6859g
Volume of liquid used
0.5ml
0.5ml
Mass of capped vial with liquid
8.0558g
7.9808g Mass of Liquid 0.3853g 0.3029g
Calculated density of acetone: D=M/V 0.3441g = 0.6882g/ml
0.5ml

Unknown liquid vial # 1
Perform three density determinations of your unknown and average the result.

Trial 1
Trial 2 Trial 3
Mass of empty, capped vial
7.6672g
8.1333g
8.1235g
Volume of liquid used
0.5ml
0.5ml
0.5ml
Mass of capped vial with liquid
8.0933g
8.5746g
8.5640g
Mass of Liquid 0.4261g 0.4413g 0.4405g

Calculated density for each trial:
0.4261+0.4413+0.4405=1.3079/2=.4360

0.4360g = 0.872g/ml
0.5ml

Determined Identity of unknown liquid based on choices in Table 1B-1: Toluene

Discuss any sources of error:
Our pipet leaked on trial 2 of acetone and this may result in a lower number

Cite references used:
Chemistry Lab Book pg. 26 Table 1b-1
Answer Questions 1-5 on page 25.
1) Use a Calibrated glass pipet
2) A) Tare out the 3-ml vial on the scale and measure out the solid using a scoopula till you reach 50mg
B) 1.0 ml calibrated pipet with a bulb
C) 0.5ml glass pipet 3) Automatic delivery pipet is more accurate and safer; the syringe uses a needle making it less accurate and more dangerous
4) So you don’t spill any liquids and it’s more precise.
5) When a liquid must be injected with a needle

Experiment C3 Purpose: To determine whether the unknown is Cinnamic acid or urea by testing the melting points.

C.3: Data and Observations:
Urea melting point=133
Cinnamic Acid melting point=133

Qualitative Observations:

Quantitative Observations:
The unknown substance from vial # 1 was used.

Cinnamic acid melting range
136.8-137.3
Unknown melting range
135.6-136.9
Mixture melting range
135.7-137.0

From this data, it was determined that the unknown was Cinnamic Acid.

Discussion of results to justify your unknown