A certain indicator, HA has a Ka value of .000050. The protonated form of the indicator is red...
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Question:
The chemical indicator:
The chemical indicator, any substance that gives a visible sign, usually by a colour change, of the presence or absence of a threshold concentration of a chemical species, such as an acid or an alkali in a solution.
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Acid-Base Indicator: Definition & Concept
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Chapter 11 / Lesson 11
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Learn about acid-base indicators. Understand what acid-base indicators are, how they work to determine if a solution is acidic or basic, and see the examples.
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- The indicator metacresol purple changes from yellow to purple at pH 8.2. At this point it exists in equal concentrations as the conjugate acid and the conjugate base. What are Ka and pKa for metacresol purple, a weak acid represented as HIn?
- Methyl red is a common acid-base indicator. It has a Ka equal to 6.3 times 10^(-6). Its unionized form is red and its anionic form is yellow. What color would a methyl red solution have at pH = 7.0? Show your calculations and explain your answers.
- 1) Phenol red is an indicator that changes color over a range from pH=6.4 to pH=8.0. What is Ka of phenol red? Express to 1 sig fig (I put 0.2 but it's wrong) 2) Alizarin yellow R, Ka=7.9x10^-12, is
- Ka is 7.9*10^-8 for bromthymol blue, an indicator that can be represented as HIn. HIn molecules are yellow, and In2 ions are blue. What color will bromthymol blue be in a solution in which (a) H3O+ = 1.0*10^-4 M, and (b) pH = 10.30?
- Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0. State what color the indicator will assume in the following solution: 0.20 m KOH.
- A weak base indicator (In) may be considered to be in equilibrium with HIn^+ and OH^ ions. The color of the non-ionized molecule is green and that of HIn is yellow. What would be the color of this indicator in a very acidic solution? Explain.
- 1) In this lab, you will be using bromothymol blue as a pH indicator. Look up the behavior and pK_a of bromothymol blue from the previous lab on indicators. a. What color change is expected in this la
- ||Indicator||Color of acid form||Color of base form||Ka value |'A'|red|yellow|1.0 x 10¯³ |'B'|yellow|blue|1.0 x 10¯⁹ What are the predominant colors of each indicator at pH 7?
- Phenolphthalein is an acid-base indicator. a. What color does it possess in the presence of excess hydrogen (i.e., hydronium) ions? b. What color does it possess in the presence of excess hydroxide ions? c. What color would you expect phenolphthalein to b
- Methyl red has the following structure: What is the color change and the pH at the color change when a weak base is titrated with a strong acid using methyl red as an indicator? For which of these two types of titrations is methyl red a possible indicator
- What is the color of a phenolphthalein indicator in an acidic solution?
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- Which of the following acid-base indicators should be used for the titration of NH3 with HBr? Kb of ammonia is 1.8 x 10^{-5}. 1. Methyl red, color change red/yellow at 4.4 less than pH less than 6.2 2. Any of these is suitable. 3. Neutral red, color ch
- Phenolphthalein has a pKa of 9.7 and is colorless in its acid form and pink in its basic form. for ph 4.7Predict the color of a phenolphthalein solution.
- Which of the following indicators would be most suitable for the titration of 0.1 M lactic acid with 0.10 M KOH(aq)? For lactic acid, pKa = 3.08. (a) thymol blue (pKin = 1.7) (b) phenol red (pKin = 7.9) (c) alizarin yellow (pKin = 11.2) (d) methyl orange
- Which of the following would be representative of being the most acidic? a. pKa = 4 b. pKa = -3 c. Ka = 1 d. Ka = 0.0001 e. Ka = 0.00000000001
- Phenolphthalein has a pKa of 9.7 and is colorless in its acid form and pink in its basic form. Calculate [In-]/[HIn] and predict the color of the phenolphthalein solution at: a. pH=4.7 b. pH= 8.2
- The indicator indigo carmine changes from blue in acid to yellow in base. It is a weak acid with a Ka of 6*10^-13. At approximately what pH does indigo carmine change color?
- What is the pKa for a compound with Ka = 10?
- What is the pKa for a compound with Ka = 102?
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- An acid turns the indicator litmus to what color?
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- What is the pKa of an acid that has a Ka of 2.72*10^-4? please show all work
- What is the Ka for a compound with pKa = 25?
- Which of the following molecules will exist in an ionized form at pH = 9.0 (look up Ka/Kb values from the last exam equation sheet if needed)? Aniline (C6H5NH2) Hypochlorous acid (HClO) Phenol (C6H
- What color would you expect to see in an acid rain sample with a pH of 5 containing methyl red indicator?
- What is the pKa value for 2,4-dinitrophenol? Is it an acid or a base?
- Butanoic acid, C3H7COOH, has a pKa of 4.82. What is the value of Ka for this acid?
- Show the reaction that represents forming a conjugate base from HPO_4^{2-}. What are the K_a and pK_a?
- The acid dissociation constant, Ka, of HSO4- is 1.2 x 10-2. What does the Ka value indicate about this compound?
- The Ka of a weak acid is 1.32 x 10-5. What is the pKa of this acid?
- The Ka of a weak acid is 2.5 x 10-6. What is the pKa of this acid?
- The Ka of a weak acid is 1.5 x 10-5. What is the pKa of this acid?
- The Ka of a weak acid is 1.48 x 10-4. What is the pKa of this acid?
- Which of the pH indicators from the following would be most appropriate for the titration of 0.30 M hydroxylamine (K_b = 9.1 x 10^{-9}) with 0.15 M hydrochloric acid? A) Methyl orange. B) Litmus. C) Thymol blue. D) trinitrobenzene. E) None.
- Give the structure for an acid-base indicator. It can be any acid-base indicator, except phenolphthalein. Explain how an acid-base indicator works (why it changes color when it does). Give the chemical reaction(s) that shows why the color changes in your
- What is the K_a for a compound with pK_a = 25? A) -25 \\B) 10^{25} \\c) 10^{-25} \\D) 0.25 \\E) \log25
- What is the Ka of butanoic acid whose pKa is 4.82?
- What is the pKa of a weak acid if Ka = 4.0 x 10-4?
- Circle which one of the following indicators you would select for a titration of a strong acid against a strong base. (i) Phenolphthalein (pH range 8.3 - 10.0, colourless \rightarrow pink) (ii) Phenol red (pH range 4.4 - 6.2, red \rightarrow yellow) (iii)
- In a triprotic acid, which Ka has the highest value? a. Ka1 b. Ka2 c. Ka3 d. all Ka have the same value
- What does the color indicate about the strength of an acid or base?
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- What other acid indicators are there other than phenolphthalein? Are there any better indicators than phenolphthalein?
- Chlorophenol red is an acid-base indicator. The conjugate acid form of the indicator is yellow and the conjugate base form is red. HCh(aq) + H2O(l) arrow Ch-(aq) + H3O+(aq) Predict which form of the indicator will be favored when a small quantity of NaOH(
- What determines the color of an acid-base indicator in an aqueous solution?
- The weak acid hippuric acid is 5.0% ionized at pH 2.3. What is the pKa of the hippuric acid?
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- Suppose you have two acids. Acid 1 has a value of Ka = 1.4 x 10-8, and acid 2 has a value of Ka = 3.3 x 10-4. Which of the two acids is stronger?
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- The value of Ka for phenol (a weak acid) is 1.00 x 10-10. What is the value of Kb for its conjugate base, C6H5O-?
- Why was phenolphthalein a good indicator to use for determining the equivalence point between the unknown weak acid and strong base?
- What is the pKa for the following weak acid equilibrium? NH4+ + H2O arrow H3O+ + NH3
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- How does an acid - base indicator such as methyl orange work in a system at equilibrium? What is the dominant species of the indicator when the solution is acid or base?
- Phenolphthalein indicator is often used for HCl/NaOH titrations. The indicator turns faint pink with the first drop of excess base. Which statement(s) correctly explains this behavior? (choose all that apply) A. The acidic form of phenolphthalein does not
- Consider the reaction between a weak acid (HA) and a weak base (B). If the pKa of HA was 4.8 and the pKa of BH+ was 10.3, what would be the value of the equilibrium constant?
- Indicators: weak acid-base equilibrium A. Water and Methyl Orange HIn = In- + H+ After the addition of 6 M HCl to the test tube, what is the color of the solution? How does the addition of HCl affe
- Which has the larger numerical value? (a) The pK_a of a strong acid or the pK_a of a weak acid (b) The K_a of a strong acid or the K_a of a weak acid
- Which indicators would be most suitable for the titration of 0.10 M lactic acid with 0.10 M KOH(aq)? For lactic acid, pKa = 3.08.
- Litmus (C_{12}H_7NO_3), shown below, is the acid-base indicator responsible for the color change that occurs with litmus
- Indicate whether a carboxylic acid (RCOOH) with a pKa value of 4.5 will have more charged molecules or more neutral molecules in a solution with the following pH :1,3,4,5,7,10,13. And explain why.
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- 1. Why is phenolphthalein an appropriate indicator for titration of a strong acid with a strong base? Explain based on the pH at the equivalent point and the transition range for phenolphthalein. 2. A
- What is the pKa for the following weak acid equilibrium? H2PO4- + H2O arrow H3O+ + HPO42-
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- A weak base has Kb = 1.5 x 10-9. What is the value of Ka for the conjugate acid?
- For the acid/base titration of HNO3 and CH3NH2, choose a suitable indicator from the list below. Beside each indicator, the pH range of colour change at its endpoint is provided. (a) methyl orange (3.1 - 4.4) (b) bromothymol (6.0 - 7.7) (c) thymolphthalei
- The value of Ka for hypochlorous acid is 3.50 x 10-8. What is the value of Kb for its conjugate base, ClO-?
- Formic acid, HCO_2H, has pK_a equals 3.75, and picric acid, C_6H_3N_3O_7, has pK_a equals 0.38. (a) What is the K_a of each? (b) Which is stronger, formic acid or picric acid?
- In an acid/base titration, why must the indicator (phenolphthalein) be a strong dye?
- What are the pka values of the acids in Dulcin (C9H12N2O2)?
- Is it possible to determine the Ka of a weak acid at points other than the halfway point of a titration? Explain.
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- Chlorophenol red is an acid-base indicator. The conjugate acid form of the indicator is yellow and the conjugate base form is red. HCh(aq) + H2O(l) arrow Ch-(aq) + H3O+(aq) Predict which form of the indicator will be favored when a small quantity of HCl(a
- Which of the following acids (listed with Ka values) and their conjugate base would form a buffer with a pH of 2.34? a. HC_{7}H_{5}O_{2}, Ka = 6.5 x 10^{-5} b. HF, Ka = 3.5 x 10^{-4} c. HClO, Ka = 2.9 x 10^{-8} d. HCN, Ka = 4.9 x 10^{-10} e. HClO_{2}, Ka
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- HNO2 is a weak acid with Ka = 4.0 x 10-4. When HNO2 is titrated with NaOH (a strong base), the pH at the equivalence point will be: a. acidic b. neutral c. basic d. not enough information
- The value of Ka for hypochlorous acid is 3.50 times 10-8. What is the value of Kb for its conjugate base, ClO-?
- The pKa values of the two ammonium cations drawn below are 8.33 and 11.1. Which pKa corresponds to which cation? Explain your choice.
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