Solids: Recrystallization and Melting Points
Solids: Recrystallization and Melting Points
Reference: Chapter 3. Solids: Recrystallization and Melting Points. Read pages 93-94 and 113-117. Experimental procedure, pages 118-119. Parts 1-3. Part 1: Melting points of Urea and Cinnamic Acid. Part 2: Melting point of unknown. Part 3: Melting point of Mixture- Urea and Cinnamic Acid (take melting points of mixtures in 1:4, 1:1 and 4:1 ratios).
Reactions
Main Reaction: Not a chemical reaction but a physical reaction. Urea in solid mixed with water melts when heated. Then through filtration and drying, the liquid mixture yields the pure Urea. This is the same main reaction for Cinnamic Acid, mixtures, and the unknown compound.
Mechanism: Recrystallization
Side Reactions: The impurities are being dissolved wither at room temperature with the addition of water and/or with heating. They remain in liquid form during the recrystallization process.
Chart
Compound
Known Melting Point Range of Pure Compounds
Experimental Melting Point Range (Slow)
Experimental Melting Point Range (Fast)
Urea
132.5-133 C
131.5-134.8 C
133.6-134 C
Cinnamic Acid
133-134.5 C
133.1-135.2 C
134-135 C
Unknown #40
209-214.8 C
210-215 C
4:1 ratio Urea to C.Acid
96.1-131.1 C
96-130.1 C
1:1 ratio Urea to C.Acid
97.7-114.8 C
98.9-111.2 C
1:4 ratio Urea to C.Acid
97.7-125.5 C
98.9-118.8
Calculations Molar mass of urea (CO(NH2)2) = 60.05526 g/mol and 1g of urea was used so converting it to moles take 1g / 60.05526g/mol = 0.0166513 moles of urea.
Molar mass of cinnimic acid (C9H8O2) is 148.16g/mol and 1g was used so converting it to moles take 1g/ 148.16g/mol = 0.00674946 moles of cinnimic acid.
Procedure
A. Calibrate Thermometer
a. Use Table 3.2 of known melting point temperatures for a series of standard substances.
b. Note the deviations from the given temperature given in Table 3.2 to that given by the thermometer. This deviation value will be applied to all temperature measurements taken.
Reference: Chapter 3. Solids: Recrystallization and Melting Points. Read pages 93-94 and 113-117. Experimental procedure, pages 118-119. Parts 1-3. Part 1: Melting points of Urea and Cinnamic Acid. Part 2: Melting point of unknown. Part 3: Melting point of Mixture- Urea and Cinnamic Acid (take melting points of mixtures in 1:4, 1:1 and 4:1 ratios).
Reactions
Main Reaction: Not a chemical reaction but a physical reaction. Urea in solid mixed with water melts when heated. Then through filtration and drying, the liquid mixture yields the pure Urea. This is the same main reaction for Cinnamic Acid, mixtures, and the unknown compound.
Mechanism: Recrystallization
Side Reactions: The impurities are being dissolved wither at room temperature with the addition of water and/or with heating. They remain in liquid form during the recrystallization process.
Chart
Compound
Known Melting Point Range of Pure Compounds
Experimental Melting Point Range (Slow)
Experimental Melting Point Range (Fast)
Urea
132.5-133 C
131.5-134.8 C
133.6-134 C
Cinnamic Acid
133-134.5 C
133.1-135.2 C
134-135 C
Unknown #40
209-214.8 C
210-215 C
4:1 ratio Urea to C.Acid
96.1-131.1 C
96-130.1 C
1:1 ratio Urea to C.Acid
97.7-114.8 C
98.9-111.2 C
1:4 ratio Urea to C.Acid
97.7-125.5 C
98.9-118.8
Calculations Molar mass of urea (CO(NH2)2) = 60.05526 g/mol and 1g of urea was used so converting it to moles take 1g / 60.05526g/mol = 0.0166513 moles of urea.
Molar mass of cinnimic acid (C9H8O2) is 148.16g/mol and 1g was used so converting it to moles take 1g/ 148.16g/mol = 0.00674946 moles of cinnimic acid.
Procedure
A. Calibrate Thermometer
a. Use Table 3.2 of known melting point temperatures for a series of standard substances.
b. Note the deviations from the given temperature given in Table 3.2 to that given by the thermometer. This deviation value will be applied to all temperature measurements taken.