Understanding Melting Points: Experiment Insights and Analysis
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Online High School**We aren't endorsed by this school
Course
CHEMISTRY 2400
Subject
Chemistry
Date
Dec 11, 2024
Pages
6
Uploaded by GeneralSwan1046
PHEMISTRY 2400 EXPERIMENT 2: MELTING poINTS STUDENT NAME: _ A\qiqa Dows EVALUATION In- Lab Techniqueg | Sample size in Capiiary | [Cleanup 55 TOTAL 10 REPORT e Maxoioints Points achieved Part 1 Results 17 Part 2 Results 2.5 Part 1 Discussion 0.6 Part 2 Discussion 1.0 Question 1 1.0 Question 2 1.8 TOTAL 9.0 TOTAL for this report = /10 Page 7of 11 FALL 2024 .
v CHEMISTRY 2409 EXPERIMENT 2: MELTING POINTS — STUDENT NAWE. e o Part1: LAB OBSERVATIONS AND TABLES PRE-LAR: Liter i ature Melting point values (TO BE COMPLETED PRIOR TO LAB): trans-cinnamic acid PRF=S °C urea_ \¥3.T ~ °C 133.0 ‘Reference: The Mesex Tadex: Mesck &0, Toe. (3013). The Mok Tader: An Eacyoispedia o Chesvicany, Drogy and Qielpgueadd | \Thy €4 . Experimental melting point ranges: trans-cinnamic acid _\33.%-133.3 = c urea 133.2-\33.0 °c your mixture of trans-cinnamic acid & urea 435,06 -\ .\ °c PROCEDURE/OBSERVATIONS: Somoples Y Fraad cindeme atd ((vowise powdery sond) | Wcea (usnite cogpawnae Jo\d) , 00d & Shktaie ¥ Yo 0 iece Hlaced QRS T0RMng RINMY capillasies. The Welvng DEAT tadgey Wece deretaraed URine e Mal-Tethg 00 with ae tlngosteT Sek o 3.3 ‘332 ms.g Page 80of 11
| g CHEMISTRY 74 - 00 STU EXPERIMENT 2: MELTING POINTS DENT NAME; FALL 2024 Part 2 T Sagis T T Unk MOWN sample couid be (A, B, C or D) _A__lit m.p. 4% -\ R litmp AT\ confirmation: sample composition experimental melting range S-3 A G8.0-\WA °¢ $-3% ¢ Q TA-%0.3 og Your unknown sample “S" is compound (A,B,C or D) A \1 PROCEDURE/OBSERVATIONS: ‘ Unkooun Samgle 3-38 (Linise | Sine Qowbes, SoWAY uagy [aced WO o ehen HEinY Copiany - The Melviag deaw TONR e Loy detecwmned Bang - Foe Mel-Tewd ODDOEAMLD 4hth Yae (heodtalr dob vo .3, Foses an Woe oodeswd MAUMng Tonge , Jowngle A ond B wete clesedy, Samgres A (wlaike, pawder e} ®od va\)\m‘a’x)m,mau«m\\“) WeTe TXRY Lokl (’mmg\e J-3F In W ti}&n;‘\’ MANNYG PAAYT CORPINAGLLT, Tae N\t\*v\hg QNN Tongey Wece detetoane WAy 3 Yae Sael-\esd QPP AALY WA Wee Thedtiar det &2 QA | | | L/ e Page 9of 11
CHEMISTRY 2400 EXPERIMENT 2: MELTING POINTS FALL 2024 DISCUSSION Part 1: Compare the experimental melting ranges to the literature melting points (where possible) and comment on the purity for each of the three samples. The literature melting point value of trans-cinnamic acid, 133°C, was very close to the experimental range of 133.8-135.2°C. Similarly, the literature melting point value of urea, 132.7°C, was near the experimental range of 133.2-135.0°C. The proximity of the literature versus experiment melting point values and the “sharp” melting point range (only varying 1-3°C) for both substances suggest that they are both pure compounds. In contrast, the sample of mixed urea and trans-cinnamic acid had a much lower and broader melting point range, from 95.6°C to 109.1°C, indicating that this was not a pure compound and, indeed a mixture. Mixtures typically have larger melting point ranges as the two components don't melt at the same rate, meaning the melting point slowly changes as the concentration changes. Part 2: Comment on the purity of the sample. Briefly explain how the identity of sample "S" was determined, including purity comments where applicable. Firstly, o determine the identity of sample S-28 it was placed into a melting point capillary to determine a rough estimate for the melting point range. The melting point range observed was 96.8-99.9°C, which was a minimal range, indicating S-28 was a pure compound. Based on this range, Samples A and B had the closest melting point ranges so the compound had to be one of those. The identity of S-28 was determined by filling two new melting point capillaries, one containing S-28 + A and one with 5-28 + B. The sample with the smallest melting point range (S-28 + A) revealed that A was the unknown compound as S-28 would have had to be mixed with itself to maintain the sharp melting point range, while S-28 + B had a much lower and broader melting point range (71.1- 80.3°C) which was nothing close to the original melting point of S-28, indicating it was a mixture. To conclude, I determined that sample S-28 was sample A, which is known as Phenanthrene. 31 Foeus
CHEMISTRY 2400 EXPERIMENT 2: MELTING POINTS FALL 2024 QUESTIONS 1. @) Why should the sample be crushed prior to packing it in to a melting point capillary? It's important to crush the sample before packing it into a melting point capillary because it increases the surface area of the sample and allows for it to heat and melt more evenly, ensuring an accurate melting point range. Additionally, if the sample is left in chunks, it may shrink while heating which can be confused for the collapse point or the initial melting point value. b) Why should the spatula be cleaned when switching to a different sample? The spatula should be cleaned when switching to a different sample to prevent cross-contamination. This is critical for testing pure compound melting points because even the smallest amount of another chemical will cause the melting point range to drop and broaden as it is now a mixture, resulting in a wider and inaccurate melting point range. c) Occasionally, you may need to repeat a melting point to verify the results. After a sample in a melting point capillary has already been heated and melted, why should the same (re-solidified) sample (in capillary) not be heated in Mel-Temp again to collect results? The same (re-solidified) sample in the melting point capillary should not be heated again in the Mel-Temp to collect results because repeated heating can alter the physical and chemical properties of the sample. The re-heated sample may have a different crystalline arrangement causing instability in the compound and altering its melting point. Additionally, some of the sample could evaporate during the initial melting which may impact its accuracy for the second run.
CHEMISTRY 2400 2 a) EXPERIMENT 2: MELTING POINTS FALL 2024 Draw th e skel N el Structures of trans-Cinnamic acid and Urea. b) If the mixture used in the mixed melting point in part 1 contains 25.32 mg of trans-cinnamic acid and 13.86 mg of urea, calculate the mole fraction (X) of each component in the mixed sample. Type response here <O - LIDND and - = " \q 0.033 3" . 3. 2330 * —2 .093399 i) ¢ R “Q ) N M \3.20mnq = 5.013%00q \} o) N 3006 9 A% Magives Mo Q: Q0N TAQ o’ ANY3IV NS X 8oy S 3.000330% w0 \ A0 \T \Q ™o Page 11 of 11