The value of Kw increases with increasing temperature. Is the autoionization of water endothermic or exothermic?
Ch.17 - Acids and Bases
Chapter 17, Problem 56
Determine the concentration of H3O+ to the correct number of significant figures in a solution with each pH. Describe how these calculations show the relationship between the number of digits to the right of the decimal place in pH and the number of significant figures in concentration. pH = 2.50 pH = 2.51 pH = 2.52

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
pH Scale
The pH scale measures the acidity or basicity of a solution, defined as the negative logarithm of the hydrogen ion concentration (H3O+). A lower pH indicates higher acidity, while a higher pH indicates lower acidity. Each unit change in pH represents a tenfold change in H3O+ concentration, making it a logarithmic scale.
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The pH Scale
Significant Figures
Significant figures are the digits in a number that contribute to its precision, including all non-zero digits, zeros between significant digits, and trailing zeros in the decimal portion. In calculations involving pH and H3O+ concentration, the number of significant figures in the pH value dictates the precision of the resulting concentration, emphasizing the importance of accurate measurement.
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Significant Figures Example
Calculating H3O+ Concentration from pH
To find the concentration of H3O+ from a given pH, the formula [H3O+] = 10^(-pH) is used. This calculation highlights the relationship between pH and H3O+ concentration, where the number of decimal places in the pH value directly corresponds to the number of significant figures in the calculated concentration. For example, a pH of 2.50 results in a concentration with three significant figures.
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pH Calculation Example
Related Practice
Textbook Question
Textbook Question
Determine whether or not the mixing of each pair of solutions results in a buffer. e. 105.0 mL of 0.15 M CH3NH2; 95.0 mL of 0.10 M HCl
Textbook Question
Calculate the pH of each acid solution. Explain how the resulting pH values demonstrate that the pH of an acid solution should carry as many digits to the right of the decimal place as the number of significant figures in the concentration of the solution. [H3O+] = 0.044 M [H3O+] = 0.045 M [H3O+] = 0.046 M
Textbook Question
For each strong acid solution, determine [H3O+], [OH–], and pH. a. 0.25 M HCl
Textbook Question
For each strong acid solution, determine [H3O+], [OH–], and pH. b. 0.015 M HNO3
Textbook Question
For each strong acid solution, determine [H3O+], [OH–], and pH. c. a solution that is 0.052 M in HBr and 0.020 M in HNO3