Chem lab 3 - In this lab, we tested how fast the rate of evaporation occurs with alcohols PDF

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In this lab, we tested how fast the rate of evaporation occurs with alcohols and alkanes. The results consist of the alcohols had a lower temperature change and alkanes had higher temperature change. The results also consisted of with a higher molar mass, the lower change in temperature resulting in...

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Pre-Lab Questions 1.Complete the following table in your laboratory notebook. Substance Formula Structural formula

Methanol

CH3OH

Molecular Weight (g/mol) 32.04

Ethanol

C2H5OH

46.07

yes

1-propanol

C3H7OH

60.095

yes

1-butanol

C4H9OH

74.121

yes

Pentane

C5H12

72.15

no

Hexane

C6H14

86.18

no

Water

H2O

18.01

yes

Acetone

C3H6O

58.08

no

Hydrogen Bond (Yes or No) yes

2.Which will evaporate faster, 1-Butanol or Pentane? Explain your choice. Pentane will evaporate faster due its only intermolecular force being Landon forces whereas 1Butanol intermolecular forces are hydrogen bonding, meaning 1-butanol has a higher boiling point making it evaporate slower. 3.A thermometer is placed in a test tube of chipped ice at -5.0 ⁰ C. The temperature is recorded at the time intervals shown below until room temperature is reached. Plot the data given below on graph paper and explain all flat, horizontal portions of the curve. Plot time on the X-axis! The temperature stays constant from the time interval of five minutes to twenty-five minutes, The temperature stays constant from the time interval of sixty-five minutes to eighty minutes.

Graph 1: The graph above shows the temperature of ice water over time. Hypothesis A substance will have a greater evaporation rate compared to another substance due to its boiling point, liquid state and molecular weight. Data and results Table 1: Temperature change during evaporation TMin (° C ) Substance TMax (° C ) Ethanol 23.8 14.9 1-Propanol 23.4 17.5

T(C) 8.9 5.9

Table 2: Comparing and predicting temperature changes during evaporation Substance Predicted Explanation TMax (° C ) TMin (° C ) T(C) Methanol 9.1 +4 23.2 10.1 1-Butanol 7.4 -5 22.5 20.1 Pentane 9.8 +6 23.0 7.2 Hexane 8.2 +6 24.5 10.3 Acetone 6.2 -3 23.3 20.1 Water 3.8 -2 23.5 21.7

T(C) 13.1 2.4 15.8 14.2 3.2 1.8

Discussion a. Correlate how readily a sample evaporated to the strength of the intermolecular forces in the molecule.5.9 If the molecules of a compound are compactly held together by strong intermolecular forces, then very few molecules will have enough kinetic energy to part from one another. The molecules will remain in a liquid phase and the rate of evaporation will not be high. b. Compare the following pairs of substances, which have nearly the same molecular weights but significantly different ΔT values, and explain this difference in terms of their intermolecular forces:...