Chapter 16: Problem 27
A student needs a sample of \(1.0 \mathrm{M} \mathrm{NaOH}\) for a laboratory experiment. Calculate the \(\left[\mathrm{H}^{+}\right],\left[\mathrm{OH}^{-}\right], \mathrm{pH}\), and \(\mathrm{pOH}\) of this solution.
Short Answer
Expert verified
[OH-] = 1.0 M, pOH = 0, pH = 14, [H+] = 10^-14 M
Step by step solution
01
- Calculate \(\backslash[ \left[ \mathrm{OH}^{-} \right] \backslash]\)
Use the given concentration of NaOH. Since NaOH dissociates completely in water: \( \left[ \mathrm{OH}^{-} \right] = 1.0 \, \mathrm{M} \)
02
- Calculate \(\backslash[ \mathrm{pOH} \backslash]\)
Use the formula for pOH: \( \mathrm{pOH} = -\log \left[ \mathrm{OH}^{-} \right] \) With \( \left[ \mathrm{OH}^{-} \right] = 1.0 \, \mathrm{M} \): \( \mathrm{pOH} = -\log \left( 1.0 \right) = 0 \)
03
- Calculate \(\backslash[ \mathrm{pH} \backslash]\)
Use the relationship between pH and pOH: \( \mathrm{pH} + \mathrm{pOH} = 14 \) Given \( \mathrm{pOH} = 0 \), \( \mathrm{pH} = 14 - 0 = 14 \)
04
- Calculate \(\backslash[ \left[ \mathrm{H}^{+} \right] \backslash]\)
Use the formula for \( \mathrm{pH} \): \( \mathrm{pH} = - \log \left[ \mathrm{H}^{+} \right] \) Given \( \mathrm{pH} = 14 \): \( \left[ \mathrm{H}^{+} \right] = 10^{-\mathrm{pH}} = 10^{-14} \, \mathrm{M} \)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
strong bases
Strong bases are substances that completely dissociate in water to produce hydroxide ions \(\text{OH}^-\). Sodium hydroxide (NaOH) is a common example of a strong base. When NaOH dissolves in water, it fully dissociates into \(Na^+\) and \(OH^-\) ions.
This property of complete dissociation ensures that if you have a 1.0 M NaOH solution, the concentration of \( \text{OH}^- \) ions will also be 1.0 M. This makes strong bases very predictable and easy to work with in calculations of pH and pOH.
Understanding this concept is key in interpreting solutions involving strong bases, as their complete dissociation simplifies the calculation of other variables, such as pH and pOH. It’s this predictability and simplicity that sets strong bases apart from weak bases, which only partially dissociate in water.
This property of complete dissociation ensures that if you have a 1.0 M NaOH solution, the concentration of \( \text{OH}^- \) ions will also be 1.0 M. This makes strong bases very predictable and easy to work with in calculations of pH and pOH.
Understanding this concept is key in interpreting solutions involving strong bases, as their complete dissociation simplifies the calculation of other variables, such as pH and pOH. It’s this predictability and simplicity that sets strong bases apart from weak bases, which only partially dissociate in water.
chemical concentration
Chemical concentration refers to the amount of a substance in a given volume of solution. It is usually expressed in moles per liter (Molarity, M).
In the context of the problem, the concentration of NaOH is given as 1.0 M. This means there is 1 mole of NaOH in every liter of solution.
Because NaOH is a strong base that dissociates completely, the \(\text{OH}^-\) ion concentration will also be 1.0 M. Understanding chemical concentration is essential as it serves as the foundational data point for calculating pH, pOH, and other properties of the solution.
To further relate, if the concentration were 0.5 M, then \(\text{OH}^-\) would also be 0.5 M. Thus, knowing how to read and interpret chemical concentrations directly impacts the success of subsequent calculations in acid-base chemistry.
In the context of the problem, the concentration of NaOH is given as 1.0 M. This means there is 1 mole of NaOH in every liter of solution.
Because NaOH is a strong base that dissociates completely, the \(\text{OH}^-\) ion concentration will also be 1.0 M. Understanding chemical concentration is essential as it serves as the foundational data point for calculating pH, pOH, and other properties of the solution.
To further relate, if the concentration were 0.5 M, then \(\text{OH}^-\) would also be 0.5 M. Thus, knowing how to read and interpret chemical concentrations directly impacts the success of subsequent calculations in acid-base chemistry.
acid-base reactions
Acid-base reactions involve the transfer of protons (H\textsuperscript{+}) between reactants. In the Bronsted-Lowry theory, acids donate protons while bases accept them.
In our example, NaOH dissociates to produce \(\text{OH}^-\) ions which can then interact with \(H^+\) ions, neutralizing them and forming water. This is a fundamental process in neutralization reactions.
Understanding acid-base reactions is crucial because they are pervasive in chemistry and many biological systems. For instance, the pH of your stomach acid is tightly regulated through acid-base reactions involving hydrochloric acid (HCl) and bicarbonate ions.
In the laboratory setting, knowing how NaOH and HCl interact can help you perform titrations—another practical application of acid-base reactions where you determine the unknown concentration of an acid or base by reacting it with a known quantity of its counterpart.
In our example, NaOH dissociates to produce \(\text{OH}^-\) ions which can then interact with \(H^+\) ions, neutralizing them and forming water. This is a fundamental process in neutralization reactions.
Understanding acid-base reactions is crucial because they are pervasive in chemistry and many biological systems. For instance, the pH of your stomach acid is tightly regulated through acid-base reactions involving hydrochloric acid (HCl) and bicarbonate ions.
In the laboratory setting, knowing how NaOH and HCl interact can help you perform titrations—another practical application of acid-base reactions where you determine the unknown concentration of an acid or base by reacting it with a known quantity of its counterpart.
dissociation in water
Dissociation refers to the process whereby molecules or ionic compounds split into smaller particles such as atoms, ions, or radicals, usually in a reversible manner. For strong acids and bases like NaOH and HCl, dissociation is complete.
When NaOH is dissolved in water, it dissociates into \(Na^+\) and \(OH^-\) ions. The extent of dissociation is critical in determining the concentration of ions in solution, which further aids in calculating pH and pOH.
This concept is essential as it explains why certain substances can significantly alter the pH of a solution. For example, when NaOH dissociates in water, it produces a high concentration of \(OH^-\) ions, making the solution very basic. Conversely, acids like HCl dissociate to produce \(H^+\) ions, making the solution acidic.
To put it simply, understanding dissociation helps explain and predict the behavior of electrolytes in water, which is foundational in chemistry and especially crucial in fields like biochemistry, environmental science, and engineering.
When NaOH is dissolved in water, it dissociates into \(Na^+\) and \(OH^-\) ions. The extent of dissociation is critical in determining the concentration of ions in solution, which further aids in calculating pH and pOH.
This concept is essential as it explains why certain substances can significantly alter the pH of a solution. For example, when NaOH dissociates in water, it produces a high concentration of \(OH^-\) ions, making the solution very basic. Conversely, acids like HCl dissociate to produce \(H^+\) ions, making the solution acidic.
To put it simply, understanding dissociation helps explain and predict the behavior of electrolytes in water, which is foundational in chemistry and especially crucial in fields like biochemistry, environmental science, and engineering.