Analysis of several plant-food preparations for potassium ion yielded the following data: Sample Percent K* 1 6.02, 6.04, 5.88, 6.06, 5.82 2 7.48, 7.47, 7.29 3.90, 3.96, 4.16, 3.96 4.48, 4.65, 4.68, 4.42 5.29, 5.13, 5.14, 5.28, 5.20 3 4 The preparations were randomly drawn from the same population. a. Find the mean and standard deviation s for each sample.

1. A sample of pure sodium oxalate, Na2C2O4 , weighing 0.2856 g is dissolved in water, sulfuric acid is added, and the solution titrated at 70°C , requiring 45.12 mL of a KMNO4 solution. The end point is overrun and back-titration is carried out with 1.74 mL of a 0.1032 N solution of oxalic acid. Calculate the normality of the KMNO4 solution. Hint: A redox reaction is involed between oxalate and permanganate. Look at the changes in oxidation state by determining the balanced redox reaction: 5C20,2 + + 2MN2+ 2 Mn04 + 10H* → 10CO2 + 8H20

An aqueous solution is made of the diprotic acid H2A to a concentration of 0.15 M H2A. Ka1 = 3.0 x 10-4 and Ka2 = 2.5 x 10-9 What is the [A2-] in this solution? Your answer should have 2 significant figures and be expressed in scientific notation (i.e. 3.0 x 10-2 as 3.0e-2)

Caculate the volume (mL) of 1.0 M potassium carbonate (K₂CO₃) needed to prepare 5.0g of the COPPER pigment. This is where the balanced chemical equation come in. You should be able to relate the moles of pigment to the moles of K₂CO₃, and from that calculate the volume of 1.0 M K₂CO₃ solution needed.  Please report your value as XX.X mL (one deicmal point and no units).

The Kjeldahl method was used to determine the nitrogen content of a protein. A 275 µL aliquot of a 47.0 mg/mL protein solution was digested in boiling sulfuric acid. The solution was made basic and the liberated NH, was collected in 5.00 mL of 0.0512 M HCl. A volume of 7.00 mL of 0.0174 M NaOH was required to react with the excess HCl. Calculate the weight percent of nitrogen in the protein. weight percent: wt% N

Consider a saturated solution of benzoic acid in water. Dichloromethane (a non-polar solvent) was added to the aqueous mixture, and the resulting mixture was mixed. After a while, a formation of two layers was observed. Given the structure of benzoic acid. Which of the following statements is TRUE? H ... H. HO H. benzoic acid A Benzoic acid will remain in the aqueous layer. B Benzoic acid will react to form sodium benzoate. Benzoic acid will be more soluble in the dichloromethane layer. D Benzoic acid will crystallize in the aqueous layer.

Exactly 10.00-mL aliquots of a solution containing phenobarbital were measured into 50.00-mL volumetric flasks and made basic with KOH. The following volumes of a standard solution of phenobarbital containing 2.000μg/mL of phenobarbital were then introduced into each flask and the mixture was diluted to volume: 0.000, 0.500, 1.00, 1.50, 2.00 mL. The fluorescence of each of these solutions was measured with a fluorimeter, which gave values of 3.26, 4.80, 6.41, 8.02, 9.56, respectively. a. plot the data.  b. derive a least squares equation for the data plotted in (a). c. find the concentration of phenobarbital from the equation in (b). d. calculate a standard deviation for the concentration obtained in (c).

Part Il: Determination of Standard Solutions mL of 0.200 mL H20 added M Cuso, diluted Tube # M Cuso4-5 H20 added Absorbance about 3 0.200 1.346 3. 4.00 1.00 0.945 4 3.00 2.00 0.715 2.00 3.00 0.469 6. 1.00 4.00 0.281 show calculation for Tube #3 diluted concentration:

Bay Water Titration The concentration of Cl- in ocean water is about 500-600 mM. The baywater is diluted by a factor of 12.5 using a 20.00 mL volumetric pipet and a 250 mL volumetric flask. Using a 15.00 mL volumetric pipet, 15.00 mL is transferred into three clean Erlenmeyer flasks. 10 mL of 1% dextrin solution, 20 mL of de-ionized water, and 3-4 drops of indicator are added and titrated each with the AgNO3 solution.  From the procedure, find:  Dilution factor Volume of diluted bay water Then calculate: The [Cl-] of diluted bay water The [Cl-] of bay water Consider this information: [AgNO3] = 0.04043177 trial # Veq 1 13.91 2 13.73 3 13.9 4 13.86 5 13.87 6 13.84     average 13.85167 [Cl-]Bay = ([AgNO3](Veq(ave))/Vdil bay water pipeted) (Vflask/Vbay water)

1. Calcium in a sample solution is determined by atomic absorption spectroscopy (AAS). A stock solution of calcium is prepared by dissolving 1.834 g CaCl, 2H,0 in water and diluting to 1 litre. From this stock solution, the second stock solution is prepared by the dilution factor of 10. Three standard solutions of calcium are prepared from the second stock solution with the following dilution factor: 20 (first standard solution), 10 (second standard solution) and 5 (third standard solution). A blank solution is prepared as well. Absorbance signals of AAS are as follows: 1.5 (blank solution), 10.6 (first standard solution), 20.1 (second standard solution), 38.5 (third standard solution), 29.6 (sample solution). (Molar mass; Ca = 40.00 g mol-, CI = 35.45 g mol-, 0 = 16.00 g mol-', H = 1.00 g mol-1) a. Construct ONE (1) plot that could be used to represent the calibration curve. b. From the plot of Q1a, determine the amount of calcium in parts per million.