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Acids, Bases and Salts
Transcript of Acids, Bases and Salts
What is common in these? Common Acids 1. Acids react with metals to produce hydrogen gas and salt.
2. Acids react with carbonates to produce carbon dioxide gas, salt and water.
3. Acids reacts with metal oxides and hydroxides to produce salt and water. Chemical Properties of Acids Strength of acids What is common in these? Common Bases 1. They react with acids to form salt and water. (Neutralisation Reaction)
The hydrogen ion from the acid and the hydroxide ion from the alkali forms water.
2. Alkalis react with most metal salts to give precipitates of metal hydroxides.
Chemical Properties of Bases Most bases are metal oxides or hydroxides.
Bases that dissolve in water are called alkalis. Strength of alkalis Alkalis can be strong or weak. Strong alkalis dissociates fully in water to give OH- ions Other Properties of acids
Acids have sour taste
Turns blue litmus paper red
Contains hydrogen ions and conducts electricity. Hydrogen ions are produced when acids dissolve in water. (ionization) The properties and reactions of acids are due to these hydrogen ions.
For example, the presence of ions causes the acid to be able to conduct electricity. Other Properties of alkalis
Alkalis have a bitter taste.
Turns red litmus paper blue
Contains hydroxide ions. Hydroxide ions are produced when alkalis dissolve in water. (ionization) The properties and reactions of alkalis are due to these hydroxide ions.
Qn: How do ammonia produce hydroxide ions in water? Ans: The pH scale measures how acidic or alkaline a solution is
ranges from 0 to 14 (zero being the most acidic and 14 being the most alkaline) Indicators have different colours in acidic and alkaline solution
Below shows commonly used indicators in titrations Salts Preparation Methods will be covered in the next lesson. produces hydrogen ions in water Note what happens when dilute hydrochloric acid is poured into the test-tube containing magnesium.
What gas is being produced?
Do you know how to test for the identity of the gas? Review Acids:
reacts with metals to produce salt and hydrogen gas
reacts with carbonates to produce salt, carbon dioxide and water
reacts with metal oxides and hydroxides to produce salt and water
produce hydrogen ions when dissolved in water
strong acids ionizes fully in water while weak acids only ionizes partially in water
has a sour taste
turn blue litmus paper red
reacts with acids to produce salt and water (neutralization)
reacts with metal salts (e.g. FeCl3) to produce precipitates of metal hydroxides
produce hydroxide ions when dissolved in water
strong alkalis ionizes fully in water while weak alkalis only ionizes partially in water
has a bitter taste
turn red litmus paper blue
pH Scale (acidic) 0 to 14 (alkaline) pH 7 is neutral.
-Universal Indicator A Univeral indicator gives different colours at different pH. Therefore the pH can be measured by dipping a piece of Universal Indicator paper in the solution anc comparing against a colour chart. Chemical Reactions of Acids and Bases
What gives acids and alkalis their properties
Strength of acids and bases
the pH scale
Indicators Overview Ammonia is an example of a weak base. When ammonia dissolves in water, only a small fraction of the ammonia molecules react with the water to form hydroxide ions. The rest remain unchanged. That is why the smell of aqueous ammonia is so strong. Homework TB Page 177 Review questions to be handed up next Monday
Read up on salt preparation