How to determine melting point depression (when measuring from the midpoint of melting point ranges). For...
How to determine melting point depression (when measuring from the midpoint of melting point ranges). For example what would be the melting point depression of a component such as benzoic acid with a crude melting point range of (108-124) and a final melting point range of (96-108).
Homework Answers
Melting point depression
When a sloid has impurities generally it melt at lower temprature compare to pure solid meling point.
Sometime a impure solid has range of melting temprature.
There are many techniques by which you can determine the depression in melting point like chalorometry experment, transmission microscope etc.
we have constrcut the phase diagrame of solind melting. In the phase diagram at the triple point ( where slolid, liquid and gas exist together, also ca;;ed eutetctic point) the solid start converting to liquid. A impure solid will have lower eutectic point compare to pure one.
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How to determine melting point depression (when measuring from
the midpoint of melting point ranges). For...
Hexachlorobenzene has a literature melting point of 231 ºC. What would be a reasonable result when...
Hexachlorobenzene has a literature melting point of 231 ºC. What would be a reasonable result when melting an impure sample of hexachlorobenzene? It would start melting around 229 ºC and finish melting around 233 ºC. It would start melting around 225 ºC, and finish melting around 230º C. The impurity would melt at whatever temperature is normal for that impurity, but the hexachlorobenzene would melt right at 231 ºC . It would melt right at a temperature lower than the...
You may have noticed that % composition vs Melting Point graphs are given in % Mole...
You may have noticed that % composition vs Melting Point graphs are given in % Mole not 96 Weight. This is because melting point depression is a colligative property (review in your general chemistry text) that depends on the moles of impurity, the same number of moles of impurity of two different compounds will cause the same melting point depression! Before the advent of mass spectrometry this was one of the techniques used to determine the molecular weight of compounds....
CHM 112 Determination of Molar Mass by Freezing Point Depression Report Sheet and Data Analysis DATA...
CHM 112 Determination of Molar Mass by Freezing Point Depression Report Sheet and Data Analysis DATA TABLE Mass of lauric acid (g) 8.003 Mass of benzoic acid (g) 1.005 Freezing temperature of pure lauric acid (°C) 42.4 Freezing point of the benzoic acid-lauric acid mixture (°C) 38.7 Discuss possible sources of error in this experiment and how those errors would affect the final calculated molar mass. This is an open ended question and a thorough answer is expected. You should...
Station 5 Compounds A, B, and C all have a melting point range of 94-96 °C. When mixed together, A and B melt at 82-95 °C. When mixed together, A and C melt at 95-97 °C a. Are compounds A and B i...
Station 5 Compounds A, B, and C all have a melting point range of 94-96 °C. When mixed together, A and B melt at 82-95 °C. When mixed together, A and C melt at 95-97 °C a. Are compounds A and B identical (yes or no) b. Are compounds A and C identical (yes or no)? c. What would you expect the melting point range for a mixture of B and C to be?
Station 5 Compounds A, B, and...
When performing a melting point on a solid compound, 2 melting point determinations were made. One...
When performing a melting point on a solid compound, 2 melting point determinations were made. One sample, which was 1 mm in height in the capillary, possessed a melting point of 150-151°C. The other sample was 25 mm in height. What would you expect the approximate melting point to be for this 25 mm sample, if the heating rate for both samples was 2 degrees per minute? (Hint: use algebra to solve the mp range) 4.
3. The melting point of unknown A was measured to be 110-120°C and unknown B was...
3. The melting point of unknown A was measured to be 110-120°C and unknown B was measured to be 105-109°C. What statement would make the best conclusion about the identity and purity of the product? (4 pts) A. Unknown A range of 110-120°C is the pure substance. Unknown B range of 105-109°C contains impurities. B. Unknown B range of 105-109°C is the pure substance. Unknown A range of 110-120°C contains impurities. C. Both Unknown A and B are pure substances....
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Recrystallization: Percent error of melting point and how impurities affect melting point: Please explain both questions...
Recrystallization: Percent error of melting point and
how impurities affect melting point:
Please explain both questions below:
(Part A) During a recrystallization experiment, the literature melting point of a compound is 105-107 °C. The melting point temperature you obtain from your recrystallized compound is 103-105 °C. Which of the following would be the proper way to set up the percent error of your mp? (a) (104/106)*100 (b) [(106-104)/106] *100 (c) (107/105)*100 (d) [(107-105)/107] *100 (Part B) For a recrystallization experiment...
Question 14 The melting point of a pure compound is known to be 110-111º. Describe the...
Question 14 The melting point of a pure compound is known to be 110-111º. Describe the melting behavior expected if this compound is contaminated with 5% of an impurity. 90-96 111-113 90-91 110-111 5 pts Question 15 You and your lab partner take melting points of the same sample. You observe a melting point of 101-107°C, while your partner observes a value of 110-112°C. Explain how you can get two different values with exactly the same sample. One of the...
separation of a three-component mixture by extraction, lab report help, the compounds are benzoic acid ,9-fluorene , and ethyl-4- aminobenzoate. I need help to write Discussion about this lab report a...
separation of a three-component mixture by extraction, lab report help, the compounds are benzoic acid ,9-fluorene , and ethyl-4- aminobenzoate. I need help to write Discussion about this lab report and I dont know what should I write.I got 25% recovary for benzoic acid ,32% for ethyl-4- aminobenzoate and 50 % recovary for 9-fluorene.( by the way I lost some product of benzoic acid). please help me full paper as you could for discussion and what is the source of...
You may have noticed that % composition vs Melting Point graphs are given in % Mole not 96 Weight. This is because melting point depression is a colligative property (review in your general chemistry text) that depends on the moles of impurity, the same number of moles of impurity of two different compounds will cause the same melting point depression! Before the advent of mass spectrometry this was one of the techniques used to determine the molecular weight of compounds....
Station 5 Compounds A, B, and C all have a melting point range of 94-96 °C. When mixed together, A and B melt at 82-95 °C. When mixed together, A and C melt at 95-97 °C a. Are compounds A and B identical (yes or no) b. Are compounds A and C identical (yes or no)? c. What would you expect the melting point range for a mixture of B and C to be?
Station 5 Compounds A, B, and...
When performing a melting point on a solid compound, 2 melting point determinations were made. One sample, which was 1 mm in height in the capillary, possessed a melting point of 150-151°C. The other sample was 25 mm in height. What would you expect the approximate melting point to be for this 25 mm sample, if the heating rate for both samples was 2 degrees per minute? (Hint: use algebra to solve the mp range) 4.
3. The melting point of unknown A was measured to be 110-120°C and unknown B was measured to be 105-109°C. What statement would make the best conclusion about the identity and purity of the product? (4 pts) A. Unknown A range of 110-120°C is the pure substance. Unknown B range of 105-109°C contains impurities. B. Unknown B range of 105-109°C is the pure substance. Unknown A range of 110-120°C contains impurities. C. Both Unknown A and B are pure substances....
Recrystallization: Percent error of melting point and
how impurities affect melting point:
Please explain both questions below:
(Part A) During a recrystallization experiment, the literature melting point of a compound is 105-107 °C. The melting point temperature you obtain from your recrystallized compound is 103-105 °C. Which of the following would be the proper way to set up the percent error of your mp? (a) (104/106)*100 (b) [(106-104)/106] *100 (c) (107/105)*100 (d) [(107-105)/107] *100 (Part B) For a recrystallization experiment...
Question 14 The melting point of a pure compound is known to be 110-111º. Describe the melting behavior expected if this compound is contaminated with 5% of an impurity. 90-96 111-113 90-91 110-111 5 pts Question 15 You and your lab partner take melting points of the same sample. You observe a melting point of 101-107°C, while your partner observes a value of 110-112°C. Explain how you can get two different values with exactly the same sample. One of the...
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