Lab 3_Caffeine_Report

19. A liquefied mixture of n-butane, n-pentane, and n-hexane has the following composition: n-C,H10 50%, n-C,H12 30%, and n-C,H14 20%. For this mixture, calculate: a) The weight fraction of each component. b) The mole fraction of each component. c) The mole percent of each component. d) The average molecular weight of the mixture.

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?

A sample of rainwater was collected from four separate locations across theMetroplex. Each sample was measured once by two separate methods for the presence ofsulfate. Determine whether the two methods are equivalent with respect to giving thesame answer for [SO42-].

1. Several procedures for the analysis of caffeine involve extracting the caffeine into an organic non-polar solvent (such as methylene chloride CH2Cl2). This about your experiment and what is discussed in the introduction. What might the advantage be for this approach? What is a disadvantage? 2. Think about what you said in the question above. If your sample was espresso, would your answer change? Why? 3. I was careless and ended up using a wavelength other than the peak (Say 250 nm). Would I still be able to carry out the experiment successfully? What might be the reason that I do not get optimum results? 4. I carried out the experiment using a scratched (or several scratches) cuvet for one standard, and clear cuvets for others. How might my calibration curve change (improve or get worse and why)? Pllllz answer these questions as soon as possible

Please do it fast

Complete the reagent table (check procedure for acid concentration) and calculate the theoretical yield. Calculate/discuss the percent yield. How efficient was the reaction? Are there any key areas in this experiment that caused a significant drop in yield? [Discussing how product was lost in the reaction rather lost in transfer steps will get the most points here] Information: 11 mmol of 2-methylcyclohexanol. 1.3 mL of 9 M sulfuric acid. Actual Yield: 0.626 grams.

2. You receive a request for 2% w/w calamine in emulsifying ointment, however you only have the 5% w/w ointment in stock. How many grams of emulsifying ointment would you need to add to 200g of 5% w/w calamine in emulsifying ointment to produce the concentration required?

Tom, an analytical chemist, bought a bag of decaffeinated coffee from a grocery store. However,Tom suspected that he might have received regular coffee and therefore decided to analyze hiscoffee for caffeine. In the lab, he took 0.5 mL of the brewed coffee and diluted it in water tomake a 100.0 mL solution. He performed four analyses and found the concentrations to be 4.69,3.99, 4.12, and 4.50 mg/L, respectively. (Assume the density of all solutions is 1.000 g/mL,1oz= 28.35 mL).(a) Report the concentration (in mg/L) of caffeine in the brewed coffee using the format asaverage ± standard deviation. (Note this is not the concentration in the diluted solution.)(b) Look up the caffeine content of regular vs. decaffeinated coffee. Do you think that Tom wasgiven the wrong type of coffee?(c) Caffeine intake of 300 mg per day reportedly has no adverse effects in the vast majority ofthe adult population. If Tom drinks 3 cups (8 oz/cup) of this coffee daily, is his intake withinthis known safe…

Table 1. Solubility Tests. Functional Group Observations (specify type if any) Sample in concentrated (+/-) H2SO4 Color orange Hydroxyl group Hydroxyl group Hydroxyl group 1-butanol Color orange 2-butanol Color orange diisopropyl ether Look at the structures of compounds tested for solubility in concentrated H2SO4. What generalization can be made for a substance to be soluble in concentrated H2SO4 ?

Stoichiometry: Prolonged exposure of some functionalities to the eluent (methanol) in this experiment may lead to undesirable reactions. In one case, Acetylsalicylic acid (Aspirin) can react with methanol to form salicylic acid and methyl acetate. If 800 mg of Acetylsalicylic acid and 1 mL of Methanol undergoes such a side reaction (known as "Methanolysis") to completion: (a) write a balanced equation (draw all molecules instead of writing chemical formulas), (b) what is the limiting reagent? (c) predict the grams of salicylic acid and methyl acetate to be produced in this process. Show calculations. Hint: you can determine the grams of 1 mL of Methanol through its density.

write an equation for this lab and explain the observations that would occur: measure out 10 mL portion of 10% sodium sulphate into a clean test tube. Add 8 drops of 50% sulphuric acid and swirl. Count the number of drops (swirl after each drop) of 30% calcium chloride needed to produce a precipitate of calcium suplhate.

1)The fat content of 10 g of commercial ice cream was determined by the Mojonnier method. The weights of the extracted fat after the second extraction and the third extraction were 1.30 and 1.36 g, respectively. How much of fat, as percentage of the total, was extracted during the third extraction?

Please help me with this, I am trying to prepare for my final exam next week and I am just completely lost

which of the following statements regarding purification by recrystallization is false? i. activated charcoal removes insoluble impurities. ii. water is the best recrystallization solvent for organic compounds. iii. slow cooling permits the exclusion of the solvent from the recrystallized solid.   a. i, ii, and iii b. i and ii c. i only d. ii and iii

10 mL of 10 % sodium sulphate solution into a clean test tube. Add 1 drop of 10 % barium chloride. What do you observe? Write an equation to explain your observations in your lab report. C2. Measure out a fresh 10 mL portion of 10 % sodium sulphate into another test tube. Making sure to count the drops, use a dropper to add 30 % calcium chloride solution. Swirl the solution after each drop. Continue until a white precipitate occurs. Write an equation to explain your observations. Which solubility product has the smaller numerical value, that for calcium sulphate or barium sulphate? Explain how you know this is true. C3. Measure out another 10 mL portion of 10 % sodium sulphate into a clean test tube. Add 8 drops of 50 % sulphuric acid and swirl. Count the number of drops (swirl after each drop) of 30 % calcium chloride needed to produce a precipitate of calcium sulphate. Explain why the number of drops of calcium chloride differs in the two experiments. I need equations, observations…

In an extraction procedure, it is advisable to: O put the aqueous layer down the drain put the organic layer in the aqueous waste throw away all layers as soon as you have extracted them save all layers until an experiment is complete

1. Calculate the exact concentration of the stock protein solution in (mg / mL) based on the exact mass of albumin and the volume of the vial used to prepare the broth.     0.4905 g of albumin in 500 mL volumetric flask (mass of protein used to prepare the stock

4. Suppose you have a mixture of saturated aqueous sodium chloride (brine) and your 2-bromo-2-methylbutane product in a separatory funnel. Use densities to predict which phase will be the top layer in the funnel. a. 2-bromo-2-methylbutane (organic phase) b. saturated sodium chloride (aqueous phase) c. hard to predict since densities are both very close to 1.18 g/mL d. there would only be one phase since the substances are miscible