Problem 74
Question
Select a strong acid, and explain how you would prepare a dilute solution of the acid. Select a weak acid, and explain how you would prepare a concentrated solution of the acid.
Step-by-Step Solution
Verified Answer
Use HCl for a dilute strong acid solution and CH₃COOH for a concentrated weak acid solution.
1Step 1: Choose a Strong Acid
A strong acid is one that completely dissociates in water. A common example is hydrochloric acid (HCl).
2Step 2: Prepare a Dilute Solution of a Strong Acid
To prepare a dilute solution of HCl, start with concentrated hydrochloric acid. Use a pipette or graduated cylinder to measure a small volume of concentrated HCl. Slowly add this volume to distilled water in a volumetric flask until you reach the desired final volume. It's important to add acid to the water, not the other way around, to prevent exothermic reactions that can be dangerous.
3Step 3: Choose a Weak Acid
A weak acid partially dissociates in water. An example of a weak acid is acetic acid (CH₃COOH).
4Step 4: Prepare a Concentrated Solution of a Weak Acid
To prepare a concentrated solution of acetic acid, start with its glacial (pure) form. Measure the desired amount of glacial acetic acid using appropriate safety equipment like goggles and gloves, as it is corrosive. Mix this volume with distilled water to achieve the desired concentration. Ensure that the lab is well-ventilated, or use a fume hood, due to the strong odor.
Key Concepts
Strong AcidWeak AcidDilute SolutionConcentrated Solution
Strong Acid
Strong acids are powerful chemicals that completely dissociate into their ions in water. This means that they release hydrogen ions, or protons, into the solution, leading to a lower pH value.
Examples of strong acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and nitric acid (HNO₃).
When preparing a solution with a strong acid, it's essential to understand the concept of dissociation. This complete breakdown in water is what characterizes a strong acid, making it highly reactive and capable of conducting electricity well.
When using strong acids:
Examples of strong acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and nitric acid (HNO₃).
When preparing a solution with a strong acid, it's essential to understand the concept of dissociation. This complete breakdown in water is what characterizes a strong acid, making it highly reactive and capable of conducting electricity well.
When using strong acids:
- Always add the acid to water, never water to acid, to avoid exothermic reactions.
- Use appropriate safety gear, such as gloves and goggles, due to their corrosive nature.
Weak Acid
Unlike strong acids, weak acids do not fully dissociate in water. This means they release fewer hydrogen ions, resulting in a higher pH compared to strong acids but still below 7.
Common examples of weak acids include acetic acid (CH₃COOH) and citric acid. These acids exist in equilibrium between their dissociated ions and undissociated molecules.
Due to their partial dissociation, they are less reactive than strong acids. However, this doesn't mean they are without risks.
When preparing a concentrated solution of a weak acid, you still need to:
Common examples of weak acids include acetic acid (CH₃COOH) and citric acid. These acids exist in equilibrium between their dissociated ions and undissociated molecules.
Due to their partial dissociation, they are less reactive than strong acids. However, this doesn't mean they are without risks.
When preparing a concentrated solution of a weak acid, you still need to:
- Handle them with care, using protective gear, because some weak acids can be irritating or corrosive, especially in concentrated forms.
- Ensure good ventilation to handle odors that may arise from acids like acetic acid.
Dilute Solution
A dilute solution contains a small amount of solute relative to the volume of solvent, which, in the case of acids, is usually water. Preparing a dilute solution involves reducing the concentration of the original solution while maintaining a consistent final volume.
To demonstrate, let's say you have concentrated hydrochloric acid (a strong acid) and you wish to make it dilute:
To demonstrate, let's say you have concentrated hydrochloric acid (a strong acid) and you wish to make it dilute:
- Start by measuring the desired volume of concentrated acid carefully.
- Next, slowly add the acid to a larger volume of water in a volumetric flask.
Concentrated Solution
A concentrated solution has a high amount of solute relative to the solvent, resulting in a higher solution concentration. When dealing with acids, this means a large quantity of acid is present in a relatively small amount of water.
To create a concentrated solution of a weak acid like acetic acid:
To create a concentrated solution of a weak acid like acetic acid:
- Begin with its pure form, such as glacial acetic acid.
- Measure the needed volume using precise equipment.
- Always use safety gear such as goggles and gloves, because even though weak acids are generally less reactive, their concentrated forms can still be dangerous.
- Work in a well-ventilated area or use a fume hood to mitigate exposure to strong fumes.
Other exercises in this chapter
Problem 71
Disinfectant Hypochlorous acid is an industrial disinfectant. Write the chemical equation and the \(K_{\text {a }}\) expression for the ionization of hypochloro
View solution Problem 73
A fictional weak base, \(\mathrm{ZaH}_{2}\) , reacts with water to yield a solution with a \(\mathrm{OH}^{-}\) ion concentration of \(2.68 \times 10^{-4}\) \(\m
View solution Problem 75
What is the relationship between the pOH and the OH- ion concentration of a solution?
View solution Problem 76
Solution A has a pH of 2.0. Solution B has a pH of 5.0. Which solution is more acidic? Based on the H+ ion concentrations in the two solutions, how many times m
View solution