3. Two laboratory staff titrated a 50.00 mL of hydrochloric acid with an unknown concentration with a standardized 0.1 N Sodium hydroxide. HCl + NaOH NaCl + H2O The students obtained the following results: Student A: 23.17 mL, 22.69 mL, 23.25 mL, 22.97 mL Student B: 25.25 mL, 25.19 mL, 25.23 mL, 25.23 mL a. (Determine the mean and standard deviation for each data set. b. Which staff was more precise? Explain. c. If the unknown HCl sample has a concentration of 0.040 M, which staff is more accurate?

3. Two laboratory staff titrated a 50.00 mL of hydrochloric acid with an unknown concentration with a standardized 0.1 N Sodium hydroxide. HCl + NaOH NaCl + H2O The students obtained the following results: Student A: 23.17 mL, 22.69 mL, 23.25 mL, 22.97 mL Student B: 25.25 mL, 25.19 mL, 25.23 mL, 25.23 mL a. (Determine the mean and standard deviation for each data set. b. Which staff was more precise? Explain. c. If the unknown HCl sample has a concentration of 0.040 M, which staff is more accurate?

Principles of Modern Chemistry

8th Edition

ISBN:9781305079113

Author:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Publisher:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Chapter11: Solutions

Section: Chapter Questions

Problem 26P

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Describe how the amount of sodium hydroxide in a mixture can be determined by titration with hydrochloric acid of known molarity.
A student is given 0.930 g of an unknown acid, which can be either oxalic acid, H2C2O4, or citric acid, H3C6H5O7. To determine which acid she has, she titrates the unknown acid with 0.615 M NaOH. The equivalence point is reached when 33.6 mL are added. What is the unknown acid?
An acid is titrated with NaOH. The following beakers are illustrations of the contents of the beaker at various times during the titration. These are presented out of order. Note: Counter-ions and water molecules have been omitted from the illustrations for clarity. (a) (b) (c) (d) (e) a. Is the acid a weak or strong acid? How can you tell? b. Arrange the beakers in order of what the contents would look like as the titration progresses. c. For which beaker would pH = pKa? Explain your answer. d. Which beaker represents the equivalence point of the titration? Explain your answer. e. For which beaker would the Ka value for the acid not be necessary to determine the pH? Explain your answer.
The calcium ions in human blood serum are necessary for coagulation (Figure 15.5). Potassium oxalate, K2C2O4, is used as an anticoagulant when a blood sample is drawn for laboratory tests because it removes the calcium as a precipitate of CaC2O4H2O. It is necessary to remove all but 1.0% of the Ca2+ in serum in order to prevent coagulation. If normal blood serum with a buffered pH of 7.40 contains 9.5 mg of Ca2+ per 100 mL of serum, what mass of K2C2O4 is required to prevent the coagulation of a 10 mL blood sample that is 55% serum by volume? (All volumes are accurate to two significant figures. Note that the volume of serum in a 10-mL blood sample is 5.5 mL. Assume that the KSp value for CaC2O4 in serum is the same as in water.) Figure 15.5 Anticoagulants can be added to blood that will combine with the Ca2+ ions in blood serum and prevent the blood from clotting. (credit: modification of work by Neeta Lind)
Three acid samples are prepared for titration by 0.01 M NaOH: 1 Sample 1 is prepared by dissolving 0.01 mol of HCl in 50 mL of water. 2 Sample 2 is prepared by dissolving 0.01 mol of HCl in 60 mL of water. 3 Sample 3 is prepared by dissolving 0.01 mol of HCl in 70 mL of water. a Without performing a formal calculation, compare the concentrations of the three acid samples (rank them from highest to lowest). b When the titration is performed, which sample, if any, will require the largest volume of the 0.01 M NaOH for neutralization?
Consider the following two acids: In two separate experiments the pH was measured during the titration of 5.00 mmol of each acid with 0.200 M NaOH. Each experiment showed only one stoichiometric point when the data were plotted. In one experiment the stoichiometric point was at 25.00 mL added NaOH, and in the other experiment the stoichiometric point was at 50.00 mL NaOH. Explain these results. (See Exercise 113.)
Use the solubility rules (Table 4.1) to decide which of the following compounds are expected to be soluble and which insoluble. a AgBr b Ca(NO3)2 c MgI2 d PbSO4
Which of the following is more likely to precipitate the hydroxide ion? Cu(OH)2(s) *=» Ctr+(aq) + 2 OH’(aq) K = 1.6 X IO-19 Ca(OH)2(s) *=» Ca2+(aq) + 2 OH’(aq) K = 7.9 X 10"6
An artificial fruit beverage contains 12.0 g of tartaric acid, H2C4H4O6, to achieve tartness. It is titrated with a basic solution that has a density of 1.045 g/cm3 and contains 5.00 mass percent KOH. What volume of the basic solution is required? (One mole of tartaric acid reacts with two moles of hydroxide ion.)
Nickel(II) formate [Ni(HCO2)2] is widely used as a catalyst precursor and to make metallic nickel. It can be prepared in the general chemistry laboratory by treating nickel(II) acetate with formic acid (HCO2H). Ni(CH3CO2)2(aq) + 2 HCO2H(aq) Ni(HCO2)2(aq) + 2 CH3CO2H(aq) Green crystalline Ni(HCO2)2 is precipitated after adding ethanol to the solution. (a) What is the theoretical yield of nickel(II) formate from 0.500 g of nickel(II) acetate and excess formic acid? (b) Is nickel(II) formate paramagnetic or diamagnetic? If it is paramagnetic, how many unpaired electrons would you expect? (c) If nickel(II) formate is heated to 300 C in the absence of air for 30 minutes, the salt decomposes to form pure nickel powder. What mass of nickel powder should be produced by heating 253 mg of nickel(II) formate? Are nickel atoms paramagnetic?
The solubility product constant for calcium oxalate is estimated to be 4 109. What is its solubility in grams per liter?
A sample of solid calcium hydroxide, Ca(OH)2, is allowed to stand in water until a saturated solution is formed. A titration of 75.00 mL of this solution with 5.00102M HCl requires 36.6 mL of the acid to reach the end point. Ca(OH)2(aq)+2HCl(aq)CaCl2(aq)+2H2O(l) What is the molarity?