Chemistry 1031 lab final

(a) To a flask, 15.0 mL of 1.25 M hydrofluoric acid is added. Then, 3.05 M NaOH is used to titrate the acid sample. Write the balanced net ionic equation for the acid-base reaction.

(#3)

For the absorbance spectrum shown, determine the analytical wavelength.

(just look at pic)

When 4.36 g of sodium hydroxide are added to 125 mL of 3.80 × 10−1 M HCl, what is the concentration, in M, of OH− in the resulting solution? You may assume the total volume of the final solution is 130 mL.

0.48MOH−

Lactic acid is a monoprotic acid with the formula C3O3H6. You have a 25.00 mL sample of lactic acid with a concentration between 1.00 M and 3.00 M. To determine the exact concentration of this sample of lactic acid, you decide to perform a titration. What titrant should you use?

1.25 M KOH

Which of the following solutions would require the most 1.5 M NaOH to neutralize it?

15.0 mL of 1.5 M sulfuric acid

A 3.458 g sample of KHP, a monoprotic acid, requires 45.71 mL of a KOH solution to reach the endpoint. What is the concentration of the KOH solution? The molar mass of KHP is 204.22 g/mol.

3.704 × 10−1MKOH

How much 2.50 M H3PO4, in mL, would you need to add to 50.00 mL of 3.50 M Ca(OH)2 in order to neutralize the solution?

46.7 mL H3PO4

During the course of a titration experiment, you notice that no matter how much base you add to the sample of acid, the color of the solution does not change. In fact, you have added three times the amount of base you expected to add! What is the next thing you should do to troubleshoot this problem?

Add a few drops of indicator to your flask. Perhaps you forgot to add them.

Wavelength, λ (nm)ε (Red, μM−1cm−1)ε (Yellow, μM−1cm−1)Absorbance5000.03690.0005490.4054300.005060.01670.474 An orange colored solution is prepared by mixing a red dye solution with a yellow dye solution and the absorbance was measured at the analytical wavelengths of 430 nm and 500 nm. The table provides the molar absorptivity for the red and yellow dye at each analytical wavelength.Calculate the concentration (in μ M) of the red and yellow dye in the mixture.[red] = μ M[yellow] = μ M

Begin by defining the two variables.x = the concentration of the red dyey = the concentration of the yellow dyeAnd then formulate the two equations using the molar absorptivity and absorbance.0.0369x + 0.000549y = 0.4050.00506x + 0.0167y = 0.474Rearrange one of the equations to isolate one variable. In this example, we will rearrange the second equation to isolate, x, the concentration of the red dye.x = 0.474 − 0.0167y0.00506Then substitute the value for x into the first equation and solve for y.0.0369x + 0.000549y = 0.4050.0369(0.474 − 0.0167y)0.00506 + 0.000549y = 0.405−0.121236y + 3.45664 = 0.405y = 25.17The concentration of the yellow dye is 25.17 μM. Plug this value back into the second equation to solve for x and the concentration of the red dye.x = 0.474 − 0.0167(25.17)0.00506 = 10.60Report the concentrations to 3 significant figures. [red] = 10.6 μM [yellow] = 25.2 μM

A student is provided with an unknown solution, which will contain one of the follow cations: Ba2+ (aq), Ca2+ (aq), Pb2+ (aq), or K+ (aq). The unknown solution is mixed with aqueous sodium chloride, sodium hydroxide, and sodium sulfate. The student's observations are shown below. NaCl (aq)NaOH (aq)Na2SO4 (aq)Unknown solutionno changeprecipitateprecipitate Which anion does the unknown solution contain?

Calcium ion, Ca2+ (aq)

A student is provided with an unknown solution, which will contain one of the follow anions: chloride (Cl−), phosphate (PO43−), or sulfate (SO42−). The unknown solution is mixed with barium nitrate, iron(III) nitrate, and silver nitrate. The student's observations are shown below. Ba(NO3)2 (aq)Fe(NO3)3 (aq)AgNO3 (aq)Unknown solutionno changeno changeprecipitate Which anion does the unknown solution contain?

Chloride, Cl−

Dye stock solutionConcentration, MBlue0.3523Yellow0.1542Red0.1017 A mixture is prepared by mixing 33.27 mL of the blue dye solution with 35.00 mL of the red dye solution and 14.73 mL of the yellow dye solution. What is the molar concentration of the blue dye in the mixture?[Blue]mixture=M

Mblue stock solution × Vblue stock solution = (0.3523 M)(0.03327 L) = 0.01172 molDetermine the total volume for the mixture in liters.Vtotal = (33.27 mL + 35.00 mL + 14.73 mL) × 1 L1000 mL = 0.08300 LCalculate the concentration of blue dye in the mixture solution.[Blue]mixture = 0.01172 mol0.08300 L = 0.1412 M

A student is provided with an unknown solution, which will contain one of the follow anions: chloride (Cl−), phosphate (PO43−), or sulfate (SO42−). The unknown solution is mixed with barium nitrate, iron(III) nitrate, and silver nitrate. The student's observations are shown below. Ba(NO3)2 (aq)Fe(NO3)3 (aq)AgNO3 (aq)Unknown solutionprecipitateprecipitateprecipitate Which anion does the unknown solution contain?

Phosphate, PO43−

A student is provided with an unknown solution, which will contain one of the follow anions: chloride (Cl−), phosphate (PO43−), or sulfate (SO42−). The unknown solution is mixed with barium nitrate, iron(III) nitrate, and silver nitrate. The student's observations are shown below. Ba(NO3)2 (aq)Fe(NO3)3 (aq)AgNO3 (aq)Unknown solutionprecipitateno changeprecipitate Which anion does the unknown solution contain?

Sulfate, SO42−

Use the calibration curve to answer the following questions. (a) The (select) is graphed on the x-axis, whereas the (select) is graphed on the y-axis. (b) The slope of the calibration curve equals . (c) The y-intercept for the calibration curve equals .

Therefore, the molar concentration is graphed on the x-axis, whereas the absorbance is graphed on the y-axis. The generic equation for a line is y = mx + b, where m is the slope and b is the y-intercept. This makes the slope of the line equal 0.337 and the y-intercept equal to 0.

Classify each ionic compound as insoluble or soluble in water. (a)Bi2(SO4) (b) PbBr2 (c) Zn(OH)2 (d) AgNO3

a. s b.i c.i d.i

Blue Blue dye stock solution0.293 MAbsorbance at 630 nm0.00265Calibration curvey = 0.0833x A solution is prepared by diluting 2.81 mL of the blue dye stock solution to 25.00 mL. The measured absorbance for the prepared solution is listed in the data table.(a) What is the theoretical molar concentration?[Blue]theoretical= × 10M(b) What is the experimental molar concentration?[Blue]experimental= × 10M(c) What is the percent error?Percent error (blue) =%

a.(0.293 M)(2.81 mL) 25.00 mL= 0.0329 M b. concentration = Abs0.0833 = 0.002650.0833 = 0.0318 M c.Percent error = |0.0318 M − 0.0329 M| 0.0329 M×100 = 3.34%

While you were cleaning the lab, you found a bottle with 150.0 mL of liquid labeled "1.50 M Sulfuric Acid." Since sulfuric acid is no longer used in your lab, your advisor asks you to prepare it for waste disposal by neutralizing it. (a) How many milliliters of a previously standardized 2.45 M NaOH would be required to neutralize this acid solution, assuming the bottle is correctly labeled? (b) After neutralizing the sample of acid, you note that it actually took 250.0 mL of base to complete the neutralization. What does this mean about the sample of the acid? (c) What is the actual concentration of the sulfuric acid if it took 250.0 mL of 2.45 M NaOH to neutralize it?

a.184 mL NaOH b.It was mislabeled. The acid solution is actually more concentrated than it says. c. 2.04 MH2SO4

(a) A dropper bottle labeled as 'solution 2' contains a pale blue liquid. Based on the color of liquid, identify the cation present in the solution. Write the net ionic equation for the reaction of aqueous copper(II) chloride with aqueous sodium phosphate. Remember to include the states of matter.

a.copper(II) ion b. (look at phone im hold one finger)

a) A dropper bottle labeled as 'solution 1' contains a pale yellow liquid. Based on the color of liquid, identify the ionic compound present in the solution. (b) Complete the total ionic equation for the reaction of aqueous iron(III) chloride with aqueous sodium hydroxide. Remember to include the states of matter for the products. Fe3+ (aq) + 3Cl− (aq) + 3Na+ (aq) + 3OH− (aq) →

a.iron(III) chloride b.( holding #2)

You perform two titrations using the same standardized solution of base. You find that 0.500 g of Acid B requires twice as much base to titrate than 0.500 g of Acid A. If the molar mass of acid A and B are the same, what can you conclude about the acids?

acid A= mono acid b= dip

y=0.337xUsing the calibration curve, calculate the molar concentration for a solution with a measured absorbance of 0.383.

concentration = 0.383/0.337 = 1.14 M

y=2755x Using the calibration curve, calculate the molar concentration for a solution with a measured absorbance of 0.455. Concentration = × 10 M

concentration = 0.455/2755 = 1.65 × 10−4 M

A student is provided with an unknown solution, which will contain one of the follow cations: Ba2+ (aq), Ca2+ (aq), Pb2+ (aq), or K+ (aq). The unknown solution is mixed with aqueous sodium chloride, sodium hydroxide, and sodium sulfate. The student's observations are shown below. NaCl (aq)NaOH (aq)Na2SO4 (aq)Unknown solutionprecipitateprecipitateprecipitate Which anion does the unknown solution contain?

lead(II)

Identify the solutions that will form a precipitate when mixed with aqueous barium chloride, BaCl2 (aq).

potassium carbonate, K2CO3 (aq) silver nitrate, AgNO3 (aq) sulfuric acid, H2SO4 (aq)

A student is provided with four dropper bottles, where each bottle is labeled as solution 1, solution 2, solution 3, or solution 4. The solution in each dropper bottle is colorless and transparent. Each of the dropper bottles will contain an aqueous solution of one of the following compounds: ammonium sulfide, calcium chloride, potassium hydroxide, or silver nitrate. After systematically mixing the four solutions, this student creates the reaction matrix shown below.

sol 1: potas sol 2: amm sol 3: calcium sol 4:silver