1040Online Dry Lab A - Online Dry Labs PDF

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Online Dry Labs...

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COMPUTER LAB: ATOMIC SPECTROSCOPY You need to go through the online experiments (three parts) step-by-step and obtain all the necessary data such as unknown number, flame colour, colour of lines and position of lines (in cm ) for the wavelength calculations. Read the position of lines up to two decimal places.

PART 1

EMISSION SPECTROSCOPY Data recorded C flame colour, colour of lines, and position of lines (cm) SINGLE Unknown number: X X X X MIXTURE Unknown number: X X X X

(4-digit #) (4-digit #)

SODIUM AS STANDARD Flame Colour:

yellow

Colour of Line:

yellow

Line Position:

24.45 cm

Wavelength:

589.3 nm

Based on Equation Î,

Calculate groove spacing “d”, if wavelength 8 = 589.3 nm (589.3 × 10 G7 cm), measured distance “a” = 24.45 cm, and length “l” = 40.0 cm.



d = 1.12994 × 103 nm = 1.13 × 103 nm

After the d value (1.13 × 10 3 nm) is obtained, the wavelength (nm) of the color band observed in each given line position (cm) can be calculated using Equation Î.

JCHU*1040

COMPUTER LAB: ATOMIC SPECTROSCOPY

PAGE - 2

R ESULTS OF F LAME T EST, C OLOUR OF L INES AND P OSITION OF L INES FROM S PECTRUM Metal Solution

Flame Colour

Line Colour

Line Position (cm)

Calculated Wavelength (nm)

Sodium

yellow

bright yellow

24.45

589.3

Lithium (Li)

red

orange red

25.65 29.50

610 671

purple

blue green yellowish orange

17.85 20.90 24.60

460 523 592

orange

green yellowish orange deep orange

22.80 24.95 26.55

560 598 625

Strontium (Sr)

red

blue bright yellow orange red

17.35 24.45 25.55 27.50

450 589 608 640

SINGLE Unknown 3333

red

orange red

25.65 29.50

610 671

yellow orange faint red red

24.45 25.60 27.50 29.50

589 609 640 671

Cesium (Cs) Calcium (Ca)

MIXTURE Unknown 7280

Î

red

SINGLE UNKNOWN

X X X X

(Record the 4-digit unknown number)

Based on the results from the flame test, colour of lines from spectrum, line positions, and calculated wavelengths, SINGLE Unknown 3333 contains: Li .

Ï

MIXTURE UNKNOWN

X X X X

(Record the 4-digit unknown number)

Based on the results from the flame test, colour of lines from spectrum, line positions, and calculated wavelengths. MIXTURE Unknown 7280 contains: Li and Sr .

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PART 2 (A)

COMPUTER LAB: ATOMIC SPECTROSCOPY

ABSORPTION SPECTROSCOPY

Spectrum of Fluorescent Lamp C Record the intensity, location and colour of the bands or lines produced by the fluorescent light. Six to eight bands should be sufficient. Line Position (cm)

Calculated Wavelength (nm)

broad bright purple

15.30

404

broad bright blue

16.65

434

faint blue

19.00

485

broad bright green

21.70

539

bright yellowish orange

24.45

589

broad faint orange

26.90

631

broad faint red

29.80

675

Colour of Lines

(B)

PAGE - 3

Effect of Concentration of Light Absorption C Record changes in the intensity, location and colour of the bands or lines produced by the fluorescent light when filtered by the KMnO 4 solution. Three major bands or lines should be sufficient.

Line Positions (cm)

Colour of Lines Fluorescent Lamp

0.005 M KMnO4

0.025 M KMnO 4

15.30

broad bright purple

broad faint purple

line disappeared

16.65

broad bright blue

broad bright blue

broad faint blue

19.00

faint blue

broad faint blue

broad very faint blue

21.80

broad bright green

narrow faint green

very narrow faint green

24.45

bright yellowish orange

broad faint yellow

line disappeared

26.90

broad faint orange

broad faint orange

broad very faint orange

29.80

broad faint red

broad faint red

broad very faint red

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C

COMPUTER LAB: ATOMIC SPECTROSCOPY

PAGE - 4

Compare the spectra of the two potassium permanganate solutions with respect to intensity and also to which lines were seen. Explain the differences.

Î

The concentrated solution showed a “weaker/dimmer” spectrum and few coloured lines. The less concentrated solution allowed more light to pass through; and less light was absorbed. The spectrum observed when light was passed through the 0.005 M KMnO4 solution is more intense than when light was passed through the 0.025 M KMnO4 solution.

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Q UESTIONS TO BE ANSWERED (i)

Relate the colour of the solution to the observed spectrum. Does the spectrum “agree” with the colour you see ? The spectrum agrees, in that the bright blue-purple lines are the same colour as the solution itself.

(ii)

Discuss the differences between the spectrum of the lamp and the spectrum of one of the KMnO 4 solution. Give a possible reason for the differences. The lamp has more coloured lines. Some of these colored lines are missing in KMnO4 because the light was absorbed by the solution.

(iii)

Do your observations regarding the two permanganate solutions in any ways support the equation, A = g c R ? Explain. Based on Beer-Lambert’s law: A = g c R the equations shows that concentration increases when the absorption is higher, if g and R are constant. The solution with higher concentration appeared to absorb more light.

Conclusions:

Higher concentration of KMnO4 solution showed more changes in the intensity, location and colour of the lines, indicating higher concentrated KMnO4 solution (0.025 M) absorbed more light.

JCHU*1040

PART 3

C

COMPUTER LAB: ATOMIC SPECTROSCOPY

PAGE - 5

EFFECT OF COMPLEXATION OF A COPPER SALT Record any changes in the intensity (brightness), location and colour of bands or lines produced by the fluorescent light when filtered by the solution. Three major bands or lines should be sufficient.

(1)

Colour of CuSO4 Solution:

light blue

(2)

Colour of CuSO4 (aq) + NH3 (aq) Solution:

deep violet

Line Positions (cm)

Fluorescent Light

CuSO 4

CuSO 4 + NH 3

light blue

deep violet

15.30

broad bright violet

broad bright violet

faint violet

16.65

broad bright blue

broad bright blue

faint blue

19.00

faint blue

faint blue

line disappeared

21.70

bright green

faint green

narrow faint green

24.45

bright yellowish orange

faint yellowish orange

line disappeared

26.90

broad faint orange

line disappeared

line disappeared

29.80

broad faint red

line disappeared

line disappeared

Observations with respect to the vial of CuSO4 , on the addition of NH3 After the addition of NH3 , the light blue solution first shows a white precipitate, and then the precipitate dissolves and the solution turns to a deep violet.

Î Ï

When copper (II) sulfate is added to water, the major species in the solutions are: Cu 2+(aq) and SO42 G(aq) . When NH 3(aq) is added to a solution of CuSO4 (aq), Cu(OH)2 (white precipitate) forms and then dissolves when more NH3 (aq) is added.

Give a possible explanation for the resultant changes in the spectrum after adding NH3 . After addition of NH3 , a new compound is formed (CuSO4 !NH3 complex), in which NH3 has absorbed the light.

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COMPUTER LAB: ATOMIC SPECTROSCOPY

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SAMPLE Marking Module: Atomic Spectroscopy Computer Lab (2 marks) Question 1 (0.4 points) The value of d represents the spacing between the grooves in the diffraction grating. You were asked to calculate the value from the sodium chloride spectrum. Enter your value for d in nanometers using 3 significant figures in the answer box provided. Do not include the units with your answer - only the numerical value. (To enter your answer in scientific notation, use 2.51e-3 for 0.00251 or 2.52e3 for 2520.) 1.13e3 Question 2 (0.3 points) Calculate the wavelength of an emission band observed at 22.5 cm with l = 40.0 cm and the grating used has a d value of 1265 nm. Enter the numerical value in nm - do NOT include the units in the space provided. 620 Question 3 (0.3 points) Unknown Sample 1: Follow these directions exactly. Within the space provide, type the 4 digit sample number, followed by two spaces, and then type the symbol for the metallic element that gives rise to the emission lines produced by unknown sample 1. For example 1234 Ce or 4532 Na Question 4 (0.4 points) Unknown Sample 2 (mixture): Follow these directions exactly. Within the space provide, enter the 4 digit sample number, followed by two spaces, and then type the symbols for the two metallic elements that give rise to the emission lines produced by unknown sample 2, separated by a space. For example 1234 Ce Li or 4532 Na Cu Question 5 (0.3 points) If a sample absorbs all wavelengths of light in the visible region, what will the color of the sample be ? black Question 6 (0.3 points) When NH3 (aq) is added to a solution of CuSO4 (aq), a. the light blue solution goes colourless b. the solution immediately turns deep violet. c. Cu(OH)2 (s) forms and then dissolves when more NH3 (aq) is added. d. a blue precipitate forms.

c

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COMPUTER LAB: ATOMIC SPECTROSCOPY

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SAMPLE Marking Module: Atomic Spectroscopy Computer Lab (2 marks) Question 1 (0.4 points) The value of d represents the spacing between the grooves in the diffraction grating. You were asked to calculate the value from the sodium chloride spectrum. Enter your value for d in nanometers using 3 significant figures in the answer box provided. Do not include the units with your answer - only the numerical value. (To enter your answer in scientific notation, use 2.51e-3 for 0.00251 or 2.52e3 for 2520.) 1.13e3 Question 2 (0.3 points) Calculate the wavelength of an emission band observed at 27.2 cm with l = 40.0 cm and the grating used has a d value of 1175 nm. Enter the numerical value in nm - do NOT include the units in the space provided. 661 Question 3 (0.3 points) Unknown Sample 1: Follow these directions exactly. Within the space provide, type the 4 digit sample number, followed by two spaces, and then type the symbol for the metallic element that gives rise to the emission lines produced by unknown sample 1. For example 1234 Ce or 4532 Na

Question 4 (0.4 points) Unknown Sample 2 (mixture): Follow these directions exactly. Within the space provide, enter the 4 digit sample number, followed by two spaces, and then type the symbols for the two metallic elements that give rise to the emission lines produced by unknown sample 2, separated by a space. For example 1234 Ce Li or 4532 Na Cu Question 5 (0.3 points) The spectrum observed when light was passed through the 0.005 M permanganate solution is less intense than when light was passed through the 0.025 M permanganate solution. Please type True or False in the answer box. False Question 6 (0.3 points) Is Mn 2+(aq) + 6 NH3 (aq) ÷ [Mn(NH3 )6 ]2+ (aq) an example of a complexation reaction ?

Yes...