Textbook Question
(b) What is the most significant difference between the sulfides precipitated in group 2 and those precipitated in group 3?
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Ch.17 - Additional Aspects of Aqueous Equilibria
Chapter 17, Problem 86
The acid–base indicator bromcresol green is a weak acid. The yellow acid and blue base forms of the indicator are present in equal concentrations in a solution when the pH is 4.68. What is the pKa for bromcresol green?
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acid-Base Indicators
Acid-base indicators are substances that change color in response to changes in pH. They are typically weak acids or bases that exhibit different colors in their protonated and deprotonated forms. For example, bromcresol green appears yellow in acidic conditions and blue in basic conditions, making it useful for determining the pH of a solution.
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04:30
Acid-Base Indicators
pKa and pH Relationship
The pKa of an acid is the negative logarithm of its acid dissociation constant (Ka) and represents the pH at which the concentrations of the protonated and deprotonated forms of the acid are equal. When the pH of a solution equals the pKa, the acid and its conjugate base are present in equal amounts, which is crucial for understanding the behavior of weak acids and bases in solution.
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02:09pH and pOH Calculations
Henderson-Hasselbalch Equation
The Henderson-Hasselbalch equation relates the pH of a solution to the pKa of an acid and the ratio of the concentrations of its deprotonated and protonated forms. It is expressed as pH = pKa + log([A-]/[HA]). This equation is particularly useful for calculating the pKa when the pH and concentrations of the acid and base forms are known, as in the case of bromcresol green.
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02:40Henderson-Hasselbalch Equation
Related Practice
Textbook Question
Derive an equation similar to the Henderson–Hasselbalch equation relating the pOH of a buffer to the pKb of its base component.
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Textbook Question
Rainwater is acidic because CO21g2 dissolves in the water, creating carbonic acid, H2CO3. If the rainwater is too acidic, it will react with limestone and seashells (which are principally made of calcium carbonate, CaCO3). Calculate the concentrations of carbonic acid, bicarbonate ion 1HCO3-2 and carbonate ion 1CO32 - 2 that are in a raindrop that has a pH of 5.60, assuming that the sum of all three species in the raindrop is 1.0 * 10-5 M.
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Textbook Question
Two buffers are prepared by adding an equal number of moles of formic acid (HCOOH) and sodium formate (HCOONa) to enough water to make 1.00 L of solution. Buffer A is prepared using 1.00 mol each of formic acid and sodium formate. Buffer B is prepared by using 0.010 mol of each. (b) Which buffer will have the greater buffer capacity?
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Textbook Question
A sample of 0.2140 g of an unknown monoprotic acid was dissolved in 25.0 mL of water and titrated with 0.0950 M NaOH. The acid required 30.0 mL of base to reach the equivalence point. (a) What is the molar mass of the acid?
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Textbook Question
A sample of 0.1687 g of an unknown monoprotic acid was dissolved in 25.0 mL of water and titrated with 0.1150 M NaOH. The acid required 15.5 mL of base to reach the equivalence point. (b) After 7.25 mL of base had been added in the titration, the pH was found to be 2.85. What is the Ka for the unknown acid?
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