Question

In the titration below acetic acid (CH CooH)i (a) What is the volume of NaOH used to neutralize the acetic ac neutralized with 0.5 M NaOH. id? (3 pts) (b) What is the concentration of the acetic acid solution? (7 pts) nial Reading 15m Burette Final Reading 32 ml NeDH (aq Known Concentraton )+20mt_灬| 1 of Total volume of 2 on vnegar ies 5 drops acetic acid 25ml c) An acid solution is titrated to the end point by a base As time goes by, the pink color disappears and the solution becomes colorless again after 30 seconds. Explain why this occurs.(4 pts) 3. a) Please refer to the UV-Vis spectra below. Explain the relationship between m and concentration. What effect does increasing concentration have on the size of silver nanoparticles formed? (8 pts) 1.0 0.6 416.9 0.2- 700 Wavelength (nm 0.6 411.8 04 0.2 0.0- 200 300 400 500 600 700 80 Wavelength (nm) b) What are some applications of silver nanoparticles? (4 pts) 4. When 8.0 g of KNOs were dissolved in 45.0 g of water at 22 °C inside a coffee-cup calorimeter the temperature of the resulting solution fell to 12.6 °C. Show all your work! (a) is this reaction endothermic or exothermic? Explain. (3 pts) (b) Calculate the heat released or absorbed by the solution chemicals (Quom) in the calorimeter (Heat capacity of calorimeter 13.7 J/C, Specific heat of the water 4.18/e'C, Density of water 1.00 g/ml). (8 pts) (c) Calculate the molar heat of reaction, AHr (kJ/mol). (K 39.10 g/mol, Ne 14.00 g/mol, O- 16.00g/mol)l 6 pts) 5. (a) Explain how percent transmittance is related to absorbance. (You can use an equation to help explain your answer(6 pts) b) What t was the purpose of graphing the absorbances of 10% cranberry juice at wavelengths 400-600 nm? (6 pts) you look at cranberry juice and at apple juice, the colors that you see are the parts of the visible spectrum that is not absorbed by the juices. What colors/parts of the visible spectrum are not absorbed? Discuss how the colors/parts that are not absorbed contribute to the colors of both the cranberry juice and apple juice. (6 pts) (a) Explain a major error that can occur in the spectrophotometry experiment. How would this error effect finding the correct--(5 pts) 6. (b) What does the term UV-Vis mean? (3 pts) ugh S1 3 rda 7. In the following chemical equations identify, which element is oxidized? Which element is reduced? (8 pts) 2NaOH H (a) 2Na +2H,0 (b) Feis) g)Fe,0,(g) 2A1.3 + 3Cu 3Cu+2 2Al + (c) 8 An ore is to be analyzed for its iron content by an oxidation-reduction titration with permanganate ion. A 4.230g sample of the ore is dissolved in hydrochloric acid before being oxidized by 31.60 ml of a 0.05120 M solution of KMNO. Calculate the amount of iron in the sample and its mass percentage in the ore. Mass of Fe 55.845 g/mol. (8 pts) oagh 9. Using the calibration curve shown below, calculate the % cranberry in an unknown sample with an absorbance of 0.280. (7 pts) 0.6 y - 2.8355x-0,0301 0.5 0.4 0.3 0.2 0.1 0.25 0.2 0.1 0.15 0.05 Volume % of Cranberry juice 1. In the titration below acetic acid (CHsCOO H) is neutralized with 0.5 M NaOH. (a) What is the volume of NaOH used to neutralize the acetic acid? (3 pts) (b) What is the concentration of the acetic acid solution? (7 pts) inial Reading 15m Burette Final Reading 32 ml Known Concentraiton 2 0mnea Total volume of 6 drops Phenaipnithacetic acid 25ml

Answer 1

a) According to the statement you started with an initial volume of 15 ml and a final reading 32 ml so:

32 - 15 = 17 ml of NaOH used or 0.017 L

we know that the concentration of the acetic acid is 0.5 M, you can calculate the number of moles of NaOH

Molarity = moles / volume

moles = molarity * volume

moles of NaOH = 0.5 * 0.017 = 0.0085 moles of NaOH used

b)according to the reaction

NaOH + CH₃COOH == CH₃COONa + H₂O, we require 1 mole of NaOH to neutralize 1 mole of CH3COOH so

we have 0.0085 moles of acetic acid in the solution

the concentration in the acetic acid solution 25 ml will be

volume = 0.025 L

Molarity = moles of acetic acid / volume =  0.0085 moles / 0.025 L = 0.34 M of acetic acid

c) phenolphtalein is an indicator that will turn pink under basic conditions, it will become colorless under acidic conditions.

When exposed to the environment your solution will get some CO₂ diluted (coming from air), the reaction will be like:

CO₂ + H₂O === H₂CO₃ , this will dissociate like

H2CO3 === H⁺ + HCO₃

The protons will neutralize the OH^- ions coming from the NaOH, this will create a slightly acid condition.