Lab 3_ Separations of Components of a Solid Misture (3)

II. b) What is the difference between liquid-liquid, solid-liquid and solid-phase extraction? Complete the table below and sort the following examples in the correct column: Steeping tea, washing an organic phase (workup), brewing beer, chemical desalting of crude oil, activated carbon sugar decolorization. liquid-liquid solid-liquid solid-phase Phase that contains analyte before extraction? Phase that contains analyte after extraction? Example(s)

Analytical chemistry is a particular field within the broader spectrum of the chemical sciences, in which many times the focus of analytical experiments is to develop new methods to analyze compounds, either structurally or by determining concentrations of compounds. One of the processes analytical chemists use to determine the exact concentration of a working solution is called standardization. In your own words, describe the differences between a primary, secondary, and tertiary standard, and describe the underlying concept behind the standardization process. Why is it done?

Explain your rationale for using the summative assessment (below) from the lesson plan on mixing substances in a 5th-grade classroom based on the below standard and learning objective, including how it aligns with the learning objective.  Summative Assessment  Summative: Components of the Lab Report Purpose: The student should clearly state the purpose of the experiment, which is to determine whether the mixing of two or more substances results in new substances. Procedure: The student should describe the steps they took to conduct the experiment. This includes the substances they chose to mix and the safety equipment they used. Observations: The student should record any observable changes that occurred when the substances were mixed. This could include a color change, the formation of a precipitate, or a change in temperature. Conclusion: The student should state whether a new substance was formed based on their observations. They should also reflect on their accuracy in…

You work in a research organization that is looking for markers of various diseases that can be used as a diagnostic for the disease. It has been reported in the past that high levels of Cu are found in the sweat of people with cystic fibrosis. One of the research projects is focused on looking for high levels of Cu in samples that can be obtained non-invasively such as saliva, sweat, hair, nails, etc. The lab will analyze large samples for Cu. What instrument would you recommend purchasing to support this work, Atomic absorption spectrophotometer or an inductively coupled plasma atomic spectrophotometer? Explain the basis for your decision.

A pheromone is a type of volatile compound produced by a variety of insect species for chemical communication. These molecules can be used to signal alarm, to attract a mate, or to indicate the presence of food. The presence of 1.00 x 10-8 g of a pheromone can be sensed by another insect within a radius of 0.500 miles. Calculate the density of this pheromone. (1609 m = 1 mile) %3D Calculate the density (g/L) of the pheromone in this cylindrical air space.

2 K₂Cr₂O7 (aq) + 8 H₂SO4 (aq) + 3 C₂H5OH(aq) --> 2 Cr₂(SO4)3 (aq) + 2 K₂SO4 (aq) + 3 CH3COOH (aq) + 11 H₂O (1) The above reaction is what occurs in a breathalyzer test. The ethanol (MM = 46.08 g/mol) reacts with the dichromate ion in potassium dichromate (MM = 294.20 g/mol) to produce the green chromate ion in chromium sulfate (MM = 392.21 g/mol). The sample is analyzed in a hand-held spectrophotometer, and the amount of light transmitted is converted into an electrical signal. The signal is then converted to an absorbance value which is proportional to the amount of ethanol in a sample. Calculate the grams of chromium sulfate formed from 0.0250 g ethanol. Enter the value with no units.

You obtain an Unknown Sample from the Stockroom.  You begin testing the solution through the steps outlined in the flowchart of the experiment’s PDF file.  You first add HCl and centrifuge your mixture.  You observe the formation of a white precipitate in the bottom of the test tube.   After pouring off the supernatant liquid, you add hot water to the white precipitate.  Addition of the hot water dissolves some of the precipitate, but some white precipitate still remains on the bottom of the test tube.  You pour off the supernatant liquid, and add ammonia (NH3) to the remaining precipitate.  You now observe the formation of a gray-black precipitate. Which of the following is a valid conclusion to draw at this point? Select one:     Hg22+ is definitely present.   Pb2+ is definitely present.   Ag+ could be present, or Hg22+ could be present, or BOTH could be present.   Ag+ is definitely present

In Lab 2, if the mass of Fe, NaCl and SiO2 recovered are 1.5g. 2.3g and 2.5g. The initial mass of the mixture before separation is 6.5g. Calculate the percent recovered of the mixture. O 23.8% O 23.1% 96.9% 103.2%

You obtain an Unknown Sample from the Stockroom.  You begin testing the solution through the steps outlined in the flowchart of the experiment’s PDF file.  You first add HCl and centrifuge your mixture.  You observe the formation of a white precipitate in the bottom of the test tube.   After pouring off the supernatant liquid, you add hot water to the white precipitate.  Addition of the hot water dissolves some of the precipitate, but some white precipitate still remains on the bottom of the test tube.   Which of the following is a valid conclusion to draw at this point?     Pb2+ is definitely present.   Hg22+ is definitely present.   Ag+ could be present, or Hg22+ could be present, or BOTH could be present.   Ag+ is definitely present

Need to find percent recovery of crude caffine and purified caffine

An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams from a heavily-contaminated river superfund site and analyze them for their Ca+ content using graphite furnace atomic absorption spectrometry (GFAAS). The chemist dried the clams at 95 °C overnight and ground them in a scientific blender, resulting in approximately 50 g of homogenized dry weight. A representative 91.79 mg sample was taken from the approximately 50 g of dry material and dissolved in 100.0 ml. of 0.1 M HCI to create a sample solution. Using the method of standard additions, the chemist prepared five standard solutions in 100.0 ml volumetric flasks, cach containing 5.00 ml. aliquots of the sample solution. Varying amounts of a 85.0 ppb (ug/L) Cd+ standard were added to each of the flasks, which were then brought to volume with 0.1 M HCI. The Cd content of the solutions was then analyzed using GFAAS, resulting in the absorbance data given in the table. TTI…

Need help to calculate for percentage % recovery

Based on this. What was the percentage error in the percentage of water in the sample, compared to pure MgSO4•7H2O?

please highlight the correct answer

A student performs a crystallization on an impure sample of biphenyl. The sample weighs 0.5 g and contains about 5% impurity. Based on his knowledge of solubility, the student decides to use benzene as the solvent. After crystallization, the crystals are dried and the nal weight is found to be 0.02 g. Assume that all steps in the crystallization are performed correctly, there are no spills, and the student lost very little solid on any glassware or in any of the transfers. Why is the recovery so low?

What is calibration and why is it essential in relation to food analysis? Provide examples.

1. Develop a detailed separation scheme for the separation and determination of the percent composition of your sample which will be a mixture of NaCl, NH.CL, and sand. You are expected to use the properties of the components listed below and some of the techniques listed in the table in the pre-lab queries (and used in Separations I). Keep in mind that any chemistry student should be able to pick up your scheme, understand it, and use it to complete the separation and calculation of % composition. Place the scheme on a separate sheet of paper. Component Solubility (@25°C) Melting Point Hardness sodium chloride, NaCl 35 g/100 mL water 801°C soft ammonium chloride, NH&Cl 37 g/100 mL water sublimes 350°C soft sand, SIQ2 insoluble 1600°C hard Example of compounds in a container. Naci NH.CI sio2 Exploring the Chemical World, PGCC, 2003 4 RESULTS Show all calculations with units in this space.

A group of third-year students, who had been growing chilli peppers at home, decided to bring samples to their Pharmacology practical where they would be measuring capsaicin, to determine which of them had grown the hottest peppers. The three students ground a sample of their peppers in 100 µl of distilled water, centrifuged the solution and then transferred the supernatant into a collection tube. One student used 70 % ethanol from a wash bottle on their bench instead of using distilled water as the extraction fluid. Samples of the collected supernatants were added to a 96 well test plate along with a range of serially diluted capsaicin standards. The students used a FlexStation which automatically added 20 µl aliquots of each supernatant onto separate wells containing 80 µl of cultured cells, which had been transfected with the capsaicin sensitive TRPV1 ion channel and preloaded with the ratiometric calcium indicator dye FURA-2 prior to the class. The FlexStation was programmed to…

11c

You obtain an Unknown Sample from the Stockroom.  You begin testing the solution through the steps outlined in the flowchart of the experiment’s PDF file.  You first add HCl and centrifuge your mixture.  You observe the formation of a white precipitate in the bottom of the test tube.   After pouring off the supernatant liquid, you add hot water to the white precipitate.  Upon addition of the hot water, you have some white precipitate still at the bottom of the test tube, and the supernatant liquid is poured off.  To this liquid, potassium chromate (K2CrO4) is added.  Upon this addition of potassium chromate, you observe no formation of precipitate. Which of the following is a valid conclusion to draw at this point? (Choose one.)   Select one:   1. Hg22+ is definitely present.   2. Pb2+ is NOT present. 3. Ag+ is definitely present. 4. Pb2+ is definitely present.

An environmental chemist working for the Environmental Protection Agency (EPA) was directed to collect razor clams from a heavily-contaminated river superfund site and analyze them for their Cd?+ content using graphite furnace atomic absorption spectrometry (GFAAS). The chemist dried the clams at 95 °C overnight and ground them in a scientific blender, resulting in approximately 50 g of homogenized dry weight. A representative 98.75 mg sample was taken from the approximately 50 g of dry material and dissolved in 100.0 mL of 0.1 M HCI to create a sample solution. Using the method of standard additions, the chemist prepared five standard solutions in 100.0 mL volumetric flasks, each containing 5.00 mL aliquots of the sample solution. Varying amounts of a 75.0 ppb (ug/L) Cd? + standard were added to each of the flasks, which were then brought to volume with 0.1 M HCI. The Cd? + content of the solutions was then analyzed using GFAAS, resulting in the. absorbance data given in the table.…

professor Scimemi has accepted you as a Master’s student and you are involved in a project that studies the cellular basis of neuropsychiatric diseases. For your electrophysiology recordings you have to make a recording solution containing (in mM): 119 NaCl, 2.5 KCl, 2.5 CaCl2, 1 MgCl2, 26.2 NaHCO3, 1 NaH2PO4, 22 glucose. You need 800 ml of it. How much KCl do you need to weigh out? Hint: we only care about KCl here. (MW KCl is 74.55 g/mol

how to separate a solid mixture of lithium bromide and barium carbonate