CIA Demonstration: Weighing on an Analytical Balance After you watch the above video, answer the questions below in sufficient detail: (a) (2 pts) What are the features of an electronic balance? Include all of those discussed in the video. Answer: Electronic balance features including electronic read-out and the tare. Electonic balance can measure mass to the precision of 0.0001. Electonic balance has the tare feature which resets a balance to zero in order to get the weight of the sample, and not the container of the sample. It has enclosed glass to contain the substance being measure (Thinkwell, 2012). (b) (1 pts) What does “tare” mean? What is the importance of the ability to ‘tare’ when taking the mass of your sample? Be specific. Answer: The tare is used when restarting the weight to 0 hence, which lets you weigh by differences.
The tare is significant since it helps to get the weight of the sample only not the weight of the sample and the container (Thinkwell, 2012). (c) (2 pts) What is the difference between weigh boats and weigh paper, and in what circumstances should you use each? Be specific and detailed in your answer. Answer: The weigh boats are containers used to stop reagents from contacting the balance area. Weigh boats which are called filter paper can be utilized as transporting vessel of the chemical to be measured. Filter papers are classified as low-cost version of the weigh boats. The material makeup of weigh boats or filter papers is polypropylene, a plastic that does not adsorb water (Thinkwell, 2012).
(d) (2 pts) According to the lab video, what is the difference in how you weigh smaller amounts vs. larger amounts, and what is the role of the scoopula in this? Explain in detail. Answer: When weighing small amounts a clean scoopula is used to add reagent to weighing paper. Tapping the scoopula delivers small amounts of the sample to the weighing paper. When weighing large amounts reagent can be poured slowly from the reagent bottle directly into the weigh boat by rolling the reagent container from side to side. The function of the scoopula is to help move solid materials. In the video, the professor used the scoopula to move potassium permanganate from a container to a weighing scale to measure it (Thinkwell, 2012). (e) (1 pts) Discuss the difference between “accuracy” and “precision”?
Answer: Accuracy is a degree of agreement between a measurement or a group of measurement and the actual value of a given quantity whereas precision is the reproducibility of a measurement of a given quantity (Thinkwell, 2012). (f) (2 pts) Suppose that your instructor gives you two samples and claims that they are both aluminum phosphide (AlP). Through a series of tricky chemical reactions, your instructor has you decompose both samples into the constituent aluminum and phosphorous, and you weigh each of your sample components on the analytical balance. You find that one sample produced 3.85 g Al and 4.42 g P, while the other produced 3.05 g Al and 3.94 g P. Are these results consistent with the law of constant composition (see Chapter 5)? Answer:
Mass Ca / Mass s 3.85g/4.42g=0.87
Mass Ca / Mass s 3.05g/3.94g=0.78
They are not consistent.
Please watch the following Thinkwell video:
15.1.4 CIA Demonstration: Distillation
After you watch the above video, answer the questions below in sufficient detail: (a) (1 pts) What is the basic concept behind the technique of distillation? How and why does it work? Be clear and specific. Answer: The basic concept behind the technique of distillation happens by sorting out a mixture of liquids or vapor combination of two or more substances into fractions of desired purity by the removal of heat. In the video the professor said that distillation begins because the vapor of a boiling mixture can contain more components that have lower boiling points. For example, in the experiment when the vapor is condensed, it contained more of volatile components, which would make the original mixture contain lower volatile material (Thinkwell, 2012). (b) (2 pts) Describe the apparatus and setup for a distillation. Include all components. Answer: The distillation apparatus consists of a round bottom flask connected through an adapter to a condenser, which is connected through another adapter to a second round-bottom flask or the collection flask.
A thermometer is used to monitor the temperature of the distillation. (Thinkwell, 2012). The components of the apparatus include adapters, columns, a reflux, condenser, reflux drum, reboiler, ring clamps, the feed and heat source. (c) (2 pts) Imagine that you wanted to perform a distillation at your own home (remember, distillation as a technique is not illegal—it is only illegal if you use it to produce alcohol), but you did not have the fancy lab equipment that you saw in the video. How could you do it? How could you improvise in terms of equipment? Explain the entire setup in detail and how the parts would work together. Answer: I want to distill apple juice at my house. I would need two containers. I would have to make sure one of the containers is transparent. I would fill the transparent container with apple juice then connect it with the other container at the neck. I would position the container so that the one with apple juice has to be in the sun so it can heat up. The other container must be kept cool in the shade and position it at an angle so that distilled apple juice will collect at the bottom. The heat would cause evaporation of the apple juice in the filled container.
Then condenses in the cooler container and then gathers as distilled water in the bottom of the container. (d) (1 pts) What is the difference between fractional and simple distillation? What is meant by “theoretical plates”? Answer: The fractional distillation consists of heating up mixture that holds different substances with different boiling points, and drawing the different fractions off as they each boil and liquefy at its own level. Simple distillation is distillation that can be utilized in breaking up liquids that have different boiling points such as liquids that vary between 10-20 degrees. Liquids that have smaller boiling points distill first and the other liquid component is left behind. In this process, vaporization and condensation occur side by side (Thinkwell, 2012). A theoretical plate when two phases of liquid and vapor phase of a given substance can reach a balance or equilibrium point with each other. In an experiment or any type of research the more theoretical plates you can show the more the efficacy of the separation process (Thinkwell, 2012). (e) (1 pts)
What is meant by “bumping”? What is meant by “reflux”? Answer: Bumping is when a solvent becomes overheated consequently discharging large vapor bubble and explosively forcing liquid outside of a flask. The reflux is constant boiling of a solution in a flask where the evaporating solvent is cooled and goes back to the original reaction flask (Thinkwell, 2012). (f) (3 pts) Suppose you performed a distillation of a solution containing 1-pentanol (C5H12O), 2-pentanol (C5H12O), 3-pentanol (C5H12O), and methyl alcohol (CH4O). All three pentanols here have the same chemical formula, but they do have a different arrangement of their atoms (i.e. they are shaped differently), so this makes them have slightly different properties from one another.
During the distillation, you collect the FIRST product that comes out, and set it aside. Then, you collect the SECOND product that comes out, and set it aside Then, you collect the THIRD product, analyze it, and determine that it has a formula mass of approximately 88 amu. What is the identity of this second product that you collected? How do you know (discuss ALL relevant data)? (HINT: You will find the table at http://www2.stetson.edu/~wgrubbs/datadriven/petermurphy/flame/table1.html very helpful when answering this question!) Answer: All of the pentanols have molecular mass that is 88. One thing that can help you to determine order of evaporation of pentanols is boiling temperature. Here is the list of pentanols and their boiling temperatures: 1-pentanol / 137-139 °C
2-pentanol / 119.3 °C,
3-pentanol / 115.3 °C
As can you see second product collected is 2-pentanol.
SCIN131 Introduction to Chemistry Lab, November 2014, Section K001. (n.d.). Retrieved November 19, 2014, from http://my.thinkwell.com/students/index.cfm