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CEM 141 Study Guide - Midterm Guide: Cathode Ray, Subatomic Particle, Boiling Point

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lemondog658
24 Feb 2020
School
MSU
Department
Chemistry
Course
CEM 141
Professor
proffessor

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Document Summary

Short answer questions: design an experiment that involves what happens when cold milk is added to hot coffee. Include: the question you would answer, an experimental design that would allow you to answer the question, the data you would collect, how you would analyze the data. *** note: there are many different possible experimental designs. Monitor the temperature as the milk is added. Collect the temperature of the hot coffee, cold milk, and the coffee/milk mixture. Plot the temperature vs. the volume of milk added. The electron was the first sub-atomic particle that was discovered (by thomson. ) Electrons are located on the outside of the atom (the nucleus is in the middle). Therefore, it is easier to remove the electrons. Electrons also have a charge so they are easier to detect than an uncharged particle (like a neutron): describe the evidence that was used to support the discovery of the electron.

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Related Questions

This Thermodynamics Lab is somewhat different from the norm. I have attached the Thermo lab that normally would be performed by the student for this Thermo class. Each student would be one of several in a small group of students taking their turn at performing an experiment on a single, small steam boiler. As may be read in the Lab Protocol, the experiment consists of measuring the temperature and pressure of the water as it is electrically heated from liquid water to vapor steam as a function of time. It is an interesting experiment BUT I think a more interesting experiment (even if it is only a Gedanken Experiment[1]) would be to transform this lab theme into a practical example. I’ve chosen a simple experiment that involves a 2 or 4-cup espresso coffee pot as a practical example of the heating and thus the pressurization of water in a closed vessel. The espresso coffee pot is used in homes and not in cafes where a more sophisticated steam generator is used to produce the rich espresso coffee (see Attachment No. 1 for “human interest” story related to this coffee pot

[1] A Gedanken Experiment was often used in the early years of the 1900’s in physics by the Leaders of theoretical physics such as Bohr, Einstein, Madame Curie, Schrodinger, Heisenberg, et al. It consists of a simple sketch and a very basic thought experiment of “…what would happen if”. It was often used when experimental apparatus was not yet available to actually do the experiment to test a hypothesis.

The coffee pot will be available for your inspection in class and the attached photo of an “exploded view” of the pot is offered for your review. If you have access of one of these pots, then your reward for actually doing the experiment will be to enjoy the coffee that is produced. However, this lab

can be completed as a simple “thought experiment” with some calculations required.

By inspecting the attached sketch you will note that the pot is actually a closed vessel once the pot is filled with water, the coffee basket/strainer is filled with coffee, and the top is tightly screwed together with the bottom that is filled water. There is a pressure relief valve shown and a gasket on the top chamber that keeps a tight seal between the top and bottom halves. The heated fluid will be forced through the coffee strainer via the inverted spout that is submerged in the water. If the experiment is successful, the espresso coffee is found in the top chamber.

The “experiment” is essentially to answer the following questions. BUT, the Lab Report should present a professional summary of the experiment using a sketch and/or photo (from any source with appropriate credit given) and any necessary calculations that was performed in order to answer the question.

Question 1. Clearly and carefully describe the heating process with a concise written description of the process. It is suggested that the description will be easier to explain if it is accompanied by a sketch of the process on a P (or T) vs. v (specific volume). Try to sketch what you believe to be the shape of the temperature change of the pot and water vs. time for the entire process. Also indicate what could happen if the source of heat is not turned-off after the coffee is produced. What is the motive force that moves the cold water to the top chamber?

Please help me with the following problem. It has many parts to it, but it is one question. Thank you in advance

Synthesis of 1-Bromobutane

Reaction Scheme

NaBr, H2SO4

CH3CH2CH2CH2OH---------------------> CH3CH2CH2CH2Br + NaHSO4 + H2O

H2O

Possible by-products:

1-butene (bp –6.3 oC), di-n-butyl ether, C4H9OC4H9, (bp 141 oC)

Properties of reagents and product:

Substance

Mol Wt. (g/mol)

Density

(g/ml)

bp, oC

Solubility

Hazards

1-butanol

74.12

.81

117-118

Sol water, Miscible alc, ether, and more

Flammable, irritant

H2SO4 (con)

98.07

1.84

280

X

corrosive material

sodium bromide

102.89

X

X

X

X

1-bromobutane

137.03

1.27

101.6

Insol in water; sol in alcohol, ether

Flammable, irritant

Quantities used in the reaction and yield data:

Substance

g or mL

Calculated moles

Theoretical Yield

moles grams

Actual Yield, grams

1-butanol

mLs

x

x

x

H2SO4 (con)

11.5 mL

x

x

x

sodium bromide

13.3 g

x

x

x

Water

15.0 mL

x

x

x

x

1-bromobutane

x

x

Want 7.5 g

A. Assume the above synthesis of 1-bromobutane is known to proceed in 75% yield and you would like to prepare 7.5 g of material. Back calculate how many mLs of 1-butanol you will need for the reaction to synthesize the 7.5 g of product, assuming that the 1-butanol is the limiting reagent. Place this number in the table. Also, calculate all the remaining missing data to fill the table.

Experimental Procedure: The NaBr, 1-butanol, and water are combined in a round-bottomed flask containing a stir bar and cooled to 0 oC. Concentrated sulfuric acid is slowly added with stirring. The reaction flask is then prepared for a 50-minute “brisk” reflux using a heating mantle. After reflux, two layers will be present. The condenser is removed and replaced with a distillation apparatus. Distill the mixture, recording the temperature range, until no more water- insoluble droplets are collected and the temperatures reaches around 115 oC. (The boiling point is elevated due to azeotropic distillation of the water with the 1-bromobutane and increasing amounts of sulfuric acid).

B. Propose a way that you could test if the droplets coming over are “water-insoluble”.

Be specific with the manipulations, glassware, and what observation you would see.

The collected liquid is transferred to a separatory funnel and 10 mL of water is added. Two layers form, the bottom being the 1-bromobutane layer. The layers are separated, one through the bottom and one through the top, and the separatory funnel is cleaned and dried. The bromobutane layer is returned to the separatory funnel and washed with ice-cold sulfuric acid to remove traces of the starting material, butene and ethereal by-products.

C. Will the top or bottom layer be the bromobutane layer when washing with concentrated sulfuric acid? Why?

The sulfuric acid layer is removed and the 1-bromobutane is washed with 10 mL 3 M NaOH followed by 10 mL aqueous sodium chloride (brine).

D. What is the purpose of each of these washes?

NaOH –

Brine -

Care should be taken to save the correct layer. The 1-bromobutane is then dried over anhydrous CaCl2.

E. How will you decide how much drying agent to use? How will you know that the 1-bromobutane is dry.

The product is distilled to obtain a clear, colorless liquid.

F. TLC – Suppose you wanted to follow the above reaction by TLC.

a. Describe how you would go about finding a good solvent or solvent pair to use.

b. Suggest a specific solvent system you would try.

c. Draw below what you would want the TLC plate to look like and show the expected relative Rf values for the 1-butanol and 1-bromobutane. Label the spots, baseline, and solvent front.