For the following questions (Q1-Q5), consider the compound tartrazine (Yellow 5 food dye) that has a chemical formula of C16H9N4Na3O9S2. Ana weighs out 0.1328 g of tartrazine powder on the balance for her experiment and makes a stock solution by dissolving her powder in 500.0 mL of solution. Q1. Determine the number of moles of tartrazine that Ana weighed out.
For the following questions (Q1-Q5), consider the compound tartrazine (Yellow 5 food dye) that has a chemical formula of C16H9N4Na3O9S2. Ana weighs out 0.1328 g of tartrazine powder on the balance for her experiment and makes a stock solution by dissolving her powder in 500.0 mL of solution.
Q1. Determine the number of moles of tartrazine that Ana weighed out.
Q2. Find the molarity (mol/L) of Ana’s tartrazine solution.
Q3. Ana makes 5 tartrazine standards by diluting her solution and measures their absorbances using a spectrophotometer:
|
Concentration (µM or µmol/L) |
Absorbance |
|
0.00 |
0.001 |
|
9.94 |
0.252 |
|
19.9 |
0.506 |
|
29.8 |
0.738 |
|
39.8 |
1.018 |
slope (m): 0.02534 1/(µM)
y-intercept (b): -0.0009147
Q4. Calculate the molar extinction coefficient (molar absorptivity) of tartrazine in units of 1/(M·cm). Assume a cuvette path length of 1.00 cm.
Q5. If Ana determines the absorbance of an unknown tartrazine sample to be 0.662, what is the concentration of the sample in µM?
For the following questions (Q6-Q10), consider the compound SOCl2, thionyl chloride.
Q6. How many valence electrons are in this molecule? 26
Q7. Draw a valid Lewis dot structure for this molecule.
Q8. Calculate formal charges for each atom.
Q9. How many non-bonding electron pairs (lone pairs) are on the central atom?
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