A 0.528 g sample of a diprotic acid with a molar mass of 255.8 g/mol is dissolved in water to a total volume of 26.0 mL . The solution is then titrated with a saturated calcium hydroxide solution. Help on part B and part C?

Part A:Assuming that the pKa values for each ionization step are sufficiently different to see two quivalence points, determine the volume of added base for the first and second equivalence points. ( answer: 1st eq:97.9mL;2nd eq:196mL)

Part B: The pH after adding 26.0 mL of the base was 3.82. Find the value of pKa1

Part C:The pH after adding 19.0 mL past the first equivalence point was 8.21. Find the value of pKa2

answers

watching

230

views

For unlimited access to Homework Help, a Homework+ subscription is required.

Join us on Discord

Chemistry Study Group

Join now

Related questions

A 0.520 g sample of a diprotic acid with a molar mass of 255.8 g/mol is dissolved in water to a total volume of 23.0 mL . The solution is then titrated with a saturated calcium hydroxide solution.

a. Assuming that the pKa values for each ionization step are sufficiently different to see two equivalence points, determine the volume of added base for the first and second equivalence points.

b. The pH after adding 23.0 mL of the base was 3.82. Find the value of pKa1.

c. The pH after adding 20.0 mL past the first equivalence point was 8.17. Find the value of pKa2.

When creating a titration curve for a weak base, the pH of the initial solution requires setting up a table showing the initial, change, and equilibrium values for each species and plugging these into the equilibrium constant expression. The expression for the bicarbonate ion is Ka1=[H2CO3][H+][HCO3â] For an anion that can both hydrolyze and produce H+, the pH of a concentrated solution can be more easily approximated using the equation pH=12(pKa1+pKa2) During the titration before the equivalence point, provided that the concentration of acid is significantly more than the concentration of base, the Henderson-Hasselbalch equation can be used to approximate the pH: pH=pKa+log[base][acid] At the equivalence point, the solution is no longer a buffer, but contains the weak acid H2CO3. The change in concentration of the bicarbonate ion is significant, and the equilibrium constant expression for Ka1 must again be used to find the concentration of hydronium ions. After the equivalence point, the strong acid will control the pH.

Part A

A 10.0-mL sample of 1.0 M NaHCO3 is titrated with 1.0 M HCl (hydrochloric acid). Approximate the titration curve by plotting the following points: pH after 0 mL HCl added, pH after 1.0 mL HCl added, pH after 9.5 mL HCl added, pH after 10.0 mL HCl added (equivalence point), pH after 10.5 mL HCl added, and pH after 12.0 mL HCl added.

1. a) A 20.00 mL sample of a diprotic acid H₂A was titrated with 0.100 M NaOH. The first equivalence point was reached after the addition of 15.00 mL of NaOH. The second equivalence point was reached after a total addition of 30.00 mL of NaOH. Use these two data points to calculate two separate values (which are in agreement) for the molarity of H₂A in the original sample. Show your work including units, specifying the species for units of moles.

b)The molecular formula for the specific diprotic acid in question one includes one mole of sulfur. How many milligrams of sulfur are present an eight ounce sample of the original acid mixture?

c) The initial pH of the diprotic acid sample in part a (before NaOH addition) was 2.61. Set up an ICE table and use this value to calculate Ka1 for the acid.

d) The species present in the analyte is H₂A (in water);

i) Write the chemical equation for the reaction that occurs when 1 mole of H₂A reacts with only one mole of Hydroxide ion (as required to reach the first equivalence point):

Besides water, what is the species present in the analyte at the 1^st equivalence point?

ii) Write the chemical equation for the reaction that occurs when the (non-water) species present at the 1^st equivalence point reacts with one mole of Hydroxide ion.

Besides water, what is the species present in the analyte at the 2^nd equivalence point?

Weekly leaderboard

Home

Homework Help 3,900,000

Chemistry 830,000

Related textbook solutions

Basic Chemistry

Principles of Chemistry Molecular Approach

Principles of Chemistry Molecular Approach

Chemistry: Structure and Properties

Chemistry: A Molecular Approach

Chemistry: A Molecular Approach

Principles of Chemistry: A Molecular Approach

Chemistry: The Central Science

Related questions

Weekly leaderboard