Exp 6

Gravimetric analysis is a quantitative method that involves measurement of volume of a solution of known concentration which is used to determine the concentration of the analyte.  True  False   A good example of complete analysis is the determination of %C, %H and %O in an unknown organic sample.  True  False

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

1a. Throughout the experiment, what are some possible sources of error that could have led to someone recovering a significantly smaller amount of table salt (NaCI) than was originally present in the sample mixture. 16. What are some possible sources of error that could have led to someone to appear to have recovered a significantly larger amount of sand (SiO2) than was originally present in the sample mixture.

please highlight the correct answer

1. Explain both precision and accuracy as they pertain to chemical measurements.  2. Why would you use the method of standard addition to calibrate a measurement instead of a calibration curve?

What are advantages and limitations of different types of modelling? (modelling with experiments, computer simulations, modelling kits and quantitative modelling)

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.

need help with doing the calculations for numbers 2,5, and 6. please check if I did calculations correctly for 7,8, and 9.

7. You have a 100 µM stock solution of dNTPs in the freezer and are setting up a PCR reaction in which you need to have a final concentration of 20 µM dNTPs. In a reaction volume of 25 μl, how much of your stock dNTPs do you add to each PCR reaction?

1. You are working with a colleague to measure the carbonate chemistry of a set of water samples. Unfortunately your colleague is a bit sloppy, and when you look at the data, you realize there must have been some errors in the measurements. Blank cells in the table below mean your colleague didn't collect data for that species in that sample. For each sample (#1-6), EITHER explain why at least some measurements for that sample must be in error OR fill in the missing data with reasonable values. (Note: you can assume the precision of the measurements is ±1mM, so inconsistencies below that level do not necessarily indicate errors.) Sample pH [H2CO3*] (MM) [HCO3] (mM) [CO3²-] (MM) Total C (mM) 1 12.0 195 199 2 3.1 155 520 3 1000 100 1101 4 7.4 317 317 50 CO 248 248 1675 6 8.3 97 402

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3. While determining the volume during this experiment (Part II), if the total volume of the flask were incorrectly reported as 125 mL, how would this error affect the calculated molar mass of the unknown volatile liquid? Explain. MacBook Air 80 DII F3 F4 F5 F6 F7 F8 F9 F10 & * 4 5 6 7 8 R Y * 00

You were tasked to separate the components of a mixture containing silica, sodium chloride and charcoal. TNāCI dissolves in water while silica and charcoal are not water-soluble. Only charcoal dissolves in carbon disulfide. a. Write a short experimental procedure to carry out the separation of the mixture. b. Given the following data, determine the percentage of charcoal, sodium chloride and silica. Mass (g) Mass of beaker 100.000 Mass of beaker + mixture 110.000 mass of evaporating dish 62.000 mass of evaporating dish + solid after evaporation of water 65.000 Mass of beaker + charcoal + silica after evaporation of excess water 117.000 mass of beaker + silica after decanting dissolved charcoal and drying 113.545

Most analytical machines used in science can either measure absorbance of light, like the spectrophotometers used BioZ 151 and 152 labs, or can measure change in electrical conductance. In order to convert things like absorbance values into concentration data, a linear regression is used. In order to determine nitrite concentration in water samples, nitrite is reacted with several chemicals to produce a purple color. The absorbance of the solution is measured from known amounts of nitrite to produce a standard curve to analyze samples. Use the data in the provided table, or from the linked spreadsheet to make a graph and perform a linear regression using treadline. mg/L NO3 Absorbance 0 0.1 0.3 0.5 0.7 o 0.183 0.542 0.914 1.298) 1.61) In order for this to work, samples must be diluted prior measurement so that the concentration falls within the range of the standard curve. If a sample underwent a 30 dilution, and produce an absorbance value of 0.953, what is the resultant concentration…

What volume of 0.220 M NaOH, in milliliters, contains 45.0 g of NaOH? Volume mL %3D

Please help with the % Error relative to label.

pour it 2. Still sleepy from a late night studying, you take the milk out of the refrigerator and pour it on your lemon juice to milk to make paneer (fresh cheese). As a group, craft a chemical explanation for the fact of coagulated milk onto your cereal. The last time you saw milk coagulate like that was when you added breakfast cereal. Unfortunately, by the time you notice the funny smell you have already poured clumps lemon juice to milk to make paneer (fresh cheese). As a group, craft a chemical explanation foea added that spoiled milk coagulates.

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