Chapter 5: Acids and bases Flashcards
What is an acid?
Acids are substances that dissociate in water to produce hydrogen ions
What happens when acids are dissolved in water?
Take for instance, HCL. When HCL is dissolved in water, HCL dissociates to form ions in the solution. The H plus ions formed gives the solution acidic properties.
What is the strength of an acid? What is the difference between a strong acid and a weak acid?
Strength is the degree of dissociation of an acid in water.
The main difference between strong and weak acids is that strong acids completely dissociate in water to produce hydrogen ions, while a weak acid partially dissociates in water to produce hydrogen ions.
In short, a strong acid will consist entirely of ions upon dissociation with no molecules remaining, while a weak acid will contain a mixture of ions and undissociated molecules in the solution.
Give 3 examples of strong and weak acid, and state their basicity
Strong acids
Hydrochloric acid, strong, mono basic
nitric acid, strong, monobasic
Sulfuric acid, strong, dibasic
Weak acids
Ethanoic acid, weak, monbasic
Carbonic acid, weak, dibasic
Phosphoric acid, weak, tribasic
What are bases? Give a general example of bases
Bases are substances that react with acids to form a salt and water.
For instance: All metal oxides and hydroxides are bases
How does solubility affect a base?
Bases soluble in water are known as ‘alkalis’, while bases that are not alkalis are known as ‘insoluble bases’
An example of alkalis are group 1 and 2 hydroxides + ammonia
An example of insoluble bases are metal oxides and hydroxides not in group 1 and 2.
What are alkalis? (Bases that are soluble in water)
Give examples of strong and weak alkalis, and state their acidity
Alkalis are substances that dissociate in water to produce hydroxide ions
Example of strong alkali:
Potassium hydroxide, strong, monoacidic
Sodium hydroxide, strong, monoacidic
Calcium hydroxide, strong, diacidic
Barium hydroxide, strong, diacidic
Example of weak alkali:
Aqueous ammonia, weak, monoacidic
What is the pH of a solution?
The pH of a solution measures the concentration of hydrogen ions
What is a pH indicator? What does working range mean?
A pH indicator is a chemical which has different colours at high pHs and at low pHs.
The working range is the range of pH values where a mixture are both colours
What are the 2 methods that can be used to measure pH?
- Use a pH meter
2. Test with universal indicator and compare the colour observed against a colour chart
What are the 3 factors that affect pH?
- The concentration of acid.- The number of acid molecules dissolved per unit volume of solvent. The concentration of acid measures the total number of undissociated and dissociated acid molecules, while pH only measures the concentration of H+ ions that are from acid molecules that are dissociated.
- Strength of acid - The degree of dissociation of an acid
A wrong acid will always have a higher pH than a weak acid. Note that an acid’s strength cannot be changed by dilution - The basicity of the acid - The maximum number of H+ ions produced per molecule of acid. (Also fixed, and cannot be changed by dilution)
