Chapter 2: Problem 15
Mathematical Calculate the hydrogen ion concentration, \(\left[\mathrm{H}^{+}\right],\) for each of the following materials: (a) Blood plasma, pH 7.4 (b) Orange juice, pH 3.5 (c) Human urine, pH 6.2 (d) Household ammonia, pH 11.5 (e) Gastric juice, pH 1.8
Short Answer
Expert verified
(a) 3.98 x 10^-8 mol/L (b) 3.16 x 10^-4 mol/L (c) 6.31 x 10^-7 mol/L (d) 3.16 x 10^-12 mol/L (e) 1.58 x 10^-2 mol/L
Step by step solution
01
- Understand the Relationship Between pH and \([\text{H}^{+}]\)
The pH of a solution is defined by the negative logarithm (base 10) of the hydrogen ion concentration: \[\text{pH} = -\text{log}_{10}[\text{H}^{+}]\]To find \([\text{H}^{+}]\) from the pH, use the inverse relationship: \[[\text{H}^{+}] = 10^{-\text{pH}}\]
02
- Calculate \([\text{H}^{+}]\) for Blood Plasma (pH 7.4)
Using the formula \([\text{H}^{+}] = 10^{-\text{pH}}\):\[[\text{H}^{+}] = 10^{-7.4}\]Calculate:\[[\text{H}^{+}] \approx 3.98 \times 10^{-8} \text{ mol/L}\]
03
- Calculate \([\text{H}^{+}]\) for Orange Juice (pH 3.5)
Using the formula \([\text{H}^{+}] = 10^{-\text{pH}}\):\[[\text{H}^{+}] = 10^{-3.5}\]Calculate:\[[\text{H}^{+}] \approx 3.16 \times 10^{-4} \text{ mol/L}\]
04
- Calculate \([\text{H}^{+}]\) for Human Urine (pH 6.2)
Using the formula \([\text{H}^{+}] = 10^{-\text{pH}}\):\[[\text{H}^{+}] = 10^{-6.2}\]Calculate:\[[\text{H}^{+}] \approx 6.31 \times 10^{-7} \text{ mol/L}\]
05
- Calculate \([\text{H}^{+}]\) for Household Ammonia (pH 11.5)
Using the formula \([\text{H}^{+}] = 10^{-\text{pH}}\):\[[\text{H}^{+}] = 10^{-11.5}\]Calculate:\[[\text{H}^{+}] \approx 3.16 \times 10^{-12} \text{ mol/L}\]
06
- Calculate \([\text{H}^{+}]\) for Gastric Juice (pH 1.8)
Using the formula \([\text{H}^{+}] = 10^{-\text{pH}}\):\[[\text{H}^{+}] = 10^{-1.8}\]Calculate:\[[\text{H}^{+}] \approx 1.58 \times 10^{-2} \text{ mol/L}\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
hydrogen ion concentration
Understanding hydrogen ion concentration is essential in acid-base chemistry. The concentration of hydrogen ions in a solution determines its acidity or alkalinity, which we often refer to in terms of pH.
To calculate the hydrogen ion concentration \(([\text{H}^+])\) from a given pH value, you use the inverse logarithmic relationship: \[ [\text{H}^+] = 10^{-\text{pH}} \] This means that if you know the pH of a solution, you can determine the concentration of hydrogen ions present.
To calculate the hydrogen ion concentration \(([\text{H}^+])\) from a given pH value, you use the inverse logarithmic relationship: \[ [\text{H}^+] = 10^{-\text{pH}} \] This means that if you know the pH of a solution, you can determine the concentration of hydrogen ions present.
- For example, blood plasma has a pH of 7.4. Using the formula, we find \[ [3.98 \times 10^{-8} \text{ mol/L}] \]
- Orange juice with a pH of 3.5 results in a hydrogen ion concentration of approximately \[ [3.16 \times 10^{-4} \text{ mol/L}] \]
logarithms in chemistry
Logarithms play a crucial role in chemistry, particularly when dealing with pH calculations. The pH scale itself is logarithmic, meaning each unit change in pH represents a tenfold change in hydrogen ion concentration.
The formula \[ \text{pH} = -\text{log}_{10}[\text{H}^+] \] shows the relationship between pH and hydrogen ion concentration. To reverse this, you use the inverse logarithm: \[ [\text{H}^{+}] = 10^{-\text{pH}} \] This is why understanding logarithms is helpful. They allow scientists to express wide-ranging concentrations in a more manageable form.
The formula \[ \text{pH} = -\text{log}_{10}[\text{H}^+] \] shows the relationship between pH and hydrogen ion concentration. To reverse this, you use the inverse logarithm: \[ [\text{H}^{+}] = 10^{-\text{pH}} \] This is why understanding logarithms is helpful. They allow scientists to express wide-ranging concentrations in a more manageable form.
- For instance, a pH of 11.5 for household ammonia results in an extremely low hydrogen ion concentration of approximately \[ [3.16 \times 10^{-12} \text{ mol/L}] \]
- Similarly, a highly acidic gastric juice with pH 1.8 has a high hydrogen ion concentration of about \[ [1.58 \times 10^{-2} \text{ mol/L}] \]
acid-base chemistry
Acid-base chemistry is a fundamental area of study that revolves around the properties of acids and bases, and how they interact. The pH scale is a critical tool in this field, ranging from 0 (very acidic) to 14 (very basic), with 7 being neutral.
The concentration of hydrogen ions \(([\text{H}^+])\) is central to determining the acidity or basicity of a solution. Acids release hydrogen ions when dissolved in water, lowering the pH, while bases absorb hydrogen ions, raising the pH.
The concentration of hydrogen ions \(([\text{H}^+])\) is central to determining the acidity or basicity of a solution. Acids release hydrogen ions when dissolved in water, lowering the pH, while bases absorb hydrogen ions, raising the pH.
- For example, human urine typically has a pH of around 6.2, making it slightly acidic. The calculated hydrogen ion concentration is approximately \[ [6.31 \times 10^{-7} \text{ mol/L}] \]
- Conversely, household ammonia, being a basic solution with a pH of 11.5, has a much lower hydrogen ion concentration