7. You are given a 500 ml solution of 0.1 M HNO3 and an indicator HIn (Ka = 3.2x10) which changes from yellow (Hin) to green (In'). If you add two drops of indicator to the solution: (a) What colour is the solution initially? (b) What pH would the colour change become visible if you were adding 0.10M NaOH?

7. You are given a 500 ml solution of 0.1 M HNO3 and an indicator HIn (Ka = 3.2x10) which changes from yellow (Hin) to green (In'). If you add two drops of indicator to the solution: (a) What colour is the solution initially? (b) What pH would the colour change become visible if you were adding 0.10M NaOH?

Introductory Chemistry: A Foundation

9th Edition

ISBN:9781337399425

Author:Steven S. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Donald J. DeCoste

Chapter16: Acids And Bases

Section: Chapter Questions

Problem 19QAP: . How is the strength of an acid related to the fact that a competition for protons exists in...

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A 10.00-g sample of the ionic compound NaA, where A is the anion of a weak acid, was dissolved in enough water to make 100.0 mL of solution and was then titrated with 0.100 M HCl. After 500.0 mL HCl was added, the pH was 5.00. The experimenter found that 1.00 L of 0.100 M HCl was required to reach the stoichiometric point of the titration. a. What is the molar mass of NaA? b. Calculate the pH of the solution at the stoichiometric point of the titration.
. How is the strength of an acid related to the fact that a competition for protons exists in aqueous solution between water molecules and the anion of the acid?
A buffer is prepared in which the ratio [ H2PO4 ]/[ HPO42 ]is 3.0. (a) What is the pH of this buffer? (b) Enough strong acid is added to convert 15% of HPO42- to H2PO4-. What is the pH of the resulting solution? (c) Enough strong base is added to make the pH 7.00. What is the ratio of [H2PO4-] to [HPO42-] at this point?
The titration of Na2CO3 with HCl bas the following qualitative profile: a. Identify the major species in solution at points AF. b. Calculate the pH at the halfway points to equivalence, B and D. (Hint: Refer to Exercise 113.)
Sketch the titration curve for a weak acid titrated by a strong base. When performing calculations concerning weak acidstrong base titrations, the general two-slep procedure is to solve a stoichiometry problem first, then to solve an equilibrium problem to determine the pH. What reaction takes place in the stoichiometry part of the problem? What is assumed about this reaction? At the various points in your titration curve, list the major species present after the strong base (NaOH, for example) reacts to completion with the weak acid, HA. What equilibrium problem would you solve at the various points in your titration curve to calculate the pH? Why is pH 7.0 at the equivalence point of a weak acid-strong base titration? Does the pH at the halfway point to equivalence have to be less than 7.0? What does the pH at the halfway point equal? Compare and contrast the titration curves for a strong acidstrong base titration and a weak acidstrong base titration.
In terms of pH indicators, please fully explain what must occur in a solution to observe a colour change?
For a titration to be effective, the reaction must be rapid and the yield of the reaction must essentially be 100%. Is Kc > 1, < 1, or ≈ 1 for a titration reaction? Kc is the product of all reaction products (choose from: Multiplied by, added to, divided by, subtracted from) the product of the reactants, with all concentrations of reactants and products raised to their respective stoichiometric powers. As the titration proceeds, the amount of reactants (choose from: Increases, decreases, remains the same) and the amount of products (choose from: Increases, decreases, remains the same). Because the value of the numerator is (Choose from much greater than, much less than, approximately equal to) the value of the denominator, the value of Kc will be (Choose from much greater than, much less than, approximately equal to)1 for an effective titration reaction.
10. 50 cm3 of 0.05 M weak acid solution is titrated with 0.1 M NaOH solution. The measured pH valuesare 7.345 and 7.497 at the consumptions of 6.0 and 6.1 cm3, respectively. What value of the buffer capacity can be calculated in the solution at pH = 7.421?11. Based on the data given in question 10, what is the total concentration of the anion of the weak acid atthe given point?
Cresol red is a pH indicator which has an acidic to basic pH and colour range of 7.0 (yellow) to 8.8 (red). The initial colour of the solution at pH 7.5 is orange and transparent. What colour would the solution change to if 20 drops of 2.5 M HCI were added to the solution?
A solution is formed by adding 6.00 grams of solid potassium acetate, KC₂H₃O₂, to 200.0 ml of 0.0240M calcium acetate, Ca(C₂H₃O₂)₂. Calculate the pH of the resulting solution. You may assume that the potassium acetate dissolve completely and that the change in volume is negligible with the addition of the solid.
What volume of 0.500 M HNO2 should be added to 500 mL of 0.750 M KNO2, so that the pH of the resulting buffer is 3.23 .
Of the following, which has the greatest buffering capacity (aq., 25 oC)? A) 0.543 M NH3 and 0.555 M NH4ClB) 0.087 M NH3 and 0.088 M NH4Cl C) 0.234 M NH3 and 0.100 M NH4ClD) 0.100 M NH3 and 0.455 M NH4Cl E) They are all buffer solutions and would all have the same capacity.