Discuss what effect, if any, would you expect the following changes to experimental conditions to have on the measured pKa value of Methyl Orange, and briefly explain your answers; a. If the experiment was carried out in solution with high ionic strength; i.e with 1M NaCl in the solution. b. If the temperature was raised by 20oC

Discuss what effect, if any, would you expect the following changes to experimental conditions to have on the measured pKa value of Methyl Orange, and briefly explain your answers; a. If the experiment was carried out in solution with high ionic strength; i.e with 1M NaCl in the solution. b. If the temperature was raised by 20oC

Appl Of Ms Excel In Analytical Chemistry

2nd Edition

ISBN:9781285686691

Author:Crouch

Publisher:Crouch

Chapter9: Complexometric And Precipitation Titrations

Section: Chapter Questions

Problem 9P

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The kinetics of hydrolysis of acetylsalicylic acid (aspirin) under certain conditions of temperature, pH, type of buffer and strength ionic, can be followed by multicomponent spectrophotometry. When performing a calculation of optical constants, the following data were obtained: Solution C. mg/100 mL A in λ (276nm) A in λ (290nm) Ac. acetylsalicylic ( AAS) 0.202 0.102 0.031 Ac. salicylic (AS) 0.198 0.158 0.101 Reaction: AAS + H2O → AS + CH3COOH In a kinetic study, after a certain time, 1 mL of the solution was taken from the reactor and diluted to 10 mL with water. distilled. Then when proceeding to the spectrophotometric measurement, the last solution presented the absorbances of 0.244 and 0.102 for the lengths of 276 and 290 nm respectively. What are the concentrations of ASA and AS in mg/L, at that instant in the reactor? Note: Acetic acid does not absorb at either wavelength.
Show how the composition of an aqueous solution that contains 20 mmol dm-3 glycine varies with pH . The pKa values for the successive acid dissociations are pKa1 = 9.60 and pKa2 = 2.35 .
Calculate the pH of a buffer solution containing 10.0 cm3 of 0.100 mol dm–3 NaOH and 20.0 cm3 of 0.500 mol dm–3 ethanoic (acetic) acid made up to a total of 50.0 cm3 in a volumetric flask at 298 K. The pKa of ethanoic acid at 298 K is 4.77
Glycolic acid is used in the textile industry as a dyeing and tanning agent. Given that its acid dissociation constant (Ka) is 1.47 × 10-4 and its partition coefficient (KD) between water and benzene is 3.22, calculate the extraction efficiency of a single extraction when 50.00 mL of a 0.025 M aqueous solution of glycolic acid buffered to a pH of 3.00, is extracted once with 50.00 mL of benzene.
5. The safonification of ethyl acetate in sodium hydroxide solution at 30^oC СНЗСООС2H5 + NaOH СНЗСОONa + С2H5ОН was studied by Smith and Lorenson (J. Am Chem. Soc.,61 (1939), 117). The initial concentration of ester alkali were both 0.05 mol.dm^-3, and the decrease in ester concentration x was measured at the following times. x 10^-3/mol dm^-3 5.91 11.42 16.30 22.07 27.17 31.47 36.44 Time/ min 4 15 24 37 53 83 Calculate the rate constant for the reaction. (Avery, 18)
Are these systems moderated, explain. A. An aqueous solution of plutonium nitrate B. A tray of uranium trioxide (UO3) powder, containing 1% moisture.
(c). The traditional way of comparing reactions is by the percentage yields. However, percentage yield takes no account of by-products. In order to decide which chemical process is greener, chemists have tried to develop ways of measuring 'greenness'. One of the most common methods is the atom economy. Calculate the atom economy of the following reactions: (1). CH2 Ph3P-CH2, + Ph3P=0 (ii). он 200 °C (iii). CI, CI .CI CI CI .CI NaOH CI CI
In a sample digested with phosphoric acid, it was found that analysis of calcium reflects less sensitivity than when digestion is done with hydrochloric acid. Explain.
3. The pKa,1 and pKa,2 of ortho and para isomers of phthalic acid (diprotic acid) are shown below: Provide an explanation on the differences of their pKa values.
6. A certain amount of methyl was hydrolysed in the presence of an excess of 0.05 mol dm -3 hydrochloric acid at 250C. When 25 cm3 aliquots of reaction mixture were removed and titrated with NaOH solution, the volume V of alkali required for neutralisation after time t were as follows. t/ min V/ cm3 24.4 25.8 29.3 Show that the reaction is first order and calculate the rate constant. (Avery, 32) 21 75 119 31.7 47.2
a) Discuss the possible mechanisms involved in the destabilization of a suspension of mineral particles upon addition of alum. The suspen- sion pH is initially 7.0, and the pH of the zero point of charge (PZC) of the particles is 6.2. Suggest three possible mechanisms for destabilization. (b) If the pH of the PZC were 9.5, would the same mechanisms apply?
13. The figure below shows three acids HX, HY and HZ, (water molecules are omitted for clarity). Which acid has the largest pKa? %3D НА 3 Н,о* НХ HY HZ А. НХ B. HY C. HZ D. it depends on the amount of acid present.