Chapter 12: Problem 34
Find the pH of the substance with the given hydronium ion concentration. Sodium bicarbonate, \(4.0 \times 10^{-9}\)
Short Answer
Expert verified
The pH of the sodium bicarbonate solution is approximately 8.40.
Step by step solution
01
- Understand the pH formula
The pH of a substance can be found using the formula: \( \text{pH} = -\text{log}[\text{H}^+] \), where \( [\text{H}^+] \) is the hydronium ion concentration.
02
- Identify the given concentration
The given hydronium ion concentration for sodium bicarbonate is \( 4.0 \times 10^{-9} \).
03
- Substitute the concentration into the pH formula
Substitute \( 4.0 \times 10^{-9} \) into the formula: \( \text{pH} = -\text{log}(4.0 \times 10^{-9}) \).
04
- Compute the logarithm
Calculate the logarithm: \( \text{log}(4.0 \times 10^{-9}) = \text{log}(4.0) + \text{log}(10^{-9}) = 0.60206 - 9 = -8.39794 \).
05
- Calculate the pH
Finally, apply the negative sign to the logarithm result: \( \text{pH} = -(-8.39794) = 8.39794 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Hydronium Ion Concentration
The hydronium ion concentration \[ [\text{H}_3\text{O}^+] \] refers to the number of hydronium ions present in a solution. Hydronium ions form when an acid dissolves in water, releasing hydrogen ions \[ (\text{H}^+) \] which then combine with water molecules \[ (\text{H}_2\text{O}) \] to form \[ \text{H}_3\text{O}^+ \]. This concentration gives us an idea of how acidic or basic a solution is.
In this example, sodium bicarbonate has a hydronium ion concentration of \[ 4.0 \times 10^{-9} \], which indicates it is a weak base.
In this example, sodium bicarbonate has a hydronium ion concentration of \[ 4.0 \times 10^{-9} \], which indicates it is a weak base.
- Lower concentrations of hydronium ions indicate a higher pH (basic solution).
- Higher concentrations of hydronium ions indicate a lower pH (acidic solution).
pH Formula
The pH formula is essential in determining how acidic or basic a solution is. The pH is calculated using: \[ \text{pH} = -\text{log}[\text{H}^+] \], where \[ [\text{H}^+] \] is the concentration of hydronium ions in the solution.
For instance, we are given a hydronium ion concentration of \[ 4.0 \times 10^{-9} \] M for sodium bicarbonate. Plugging this into the formula:
For instance, we are given a hydronium ion concentration of \[ 4.0 \times 10^{-9} \] M for sodium bicarbonate. Plugging this into the formula:
- \[ \text{pH} = -\text{log}(4.0 \times 10^{-9}) \]
- Applying logarithm rules, we split it into two parts: \[ \text{log}(4.0) + \text{log}(10^{-9}) \]
Logarithm in Chemistry
Using a logarithm function in chemistry is common for dealing with a wide range of concentration values. A logarithm (log) helps transform large variations in values into more manageable numbers.
For pH calculation:
For pH calculation:
- \[ \text{log}(4.0 \times 10^{-9}) = \text{log}(4.0) + \text{log}(10^{-9}) = 0.60206 - 9 \]
- Here, \[ \text{log}(4.0) \] is approximately 0.60206 and \[ \text{log}(10^{-9}) = -9 \].
- Combining these gives us: \[ \text{log}(4.0 \times 10^{-9}) = -8.39794 \]
Acid-Base Chemistry
Acid-base chemistry explores the properties and reactions of acids and bases. An acid increases the hydronium ion concentration in a solution, while a base decreases it by increasing the hydroxide ion concentration.
The pH scale ranges from 0 to 14 and provides a measure of acidity or basicity:
The pH scale ranges from 0 to 14 and provides a measure of acidity or basicity:
- pH < 7: Acidic solution
- pH = 7: Neutral solution
- pH > 7: Basic solution