Properties of acids and bases Flashcards
1
Q
What happens when acids react with metals?
A
- Produce salt and hydrogen gas
- metal + acid → salt + hydrogen
- Unreactive metals (below H2 on the reactivity series) tend not to react with dilute acids
2
Q
How do you test for hydrogen gas?
A
- Ignite a splint and hold it over the container with the gas. If H2 is present, it should make a squeaky pop sound
3
Q
What are the products when metal carbonates and hydrogen carbonates react with acids?
A
- Products: salt, water and CO2
4
Q
How do you test for CO2 gas?
A
- Bubbling the gas through an aqueous solution of calcium hydroxide, Ca(OH)2 (limewater)
- If CO2 is present, the limewater turns milky
5
Q
What are neutralisation reactions?
A
- Reactions between acids with alkalis/bases, result in salt and water
- Bases include metal hydroxides, metal oxides and aqueous ammonia
- Exothermic reactions, negative enthalpy change
6
Q
What are antacids?
A
- Tablets that ease the symptoms of excess stomach acid that causes indigestion
- The ingredients include metal or hydrogen carbonates
- They react with the stomach acid and neutralise to relieve the symptoms
7
Q
What is an acid-base titration?
A
- To determine the unknown concentrations of an acidic or a base solution using a solution of known concentration
- Use acid-base indicator to determine the point at which the acid neutralises the base
8
Q
What indicator and why is used in acid-base titrations?
A
- Phenolphthalein which changes from colourless to pink
- It is naturally colourless, but turns pink in presence of a base (when base is in burette)
- When acid is in burette, changes from pink to colourless
- Used because of the bright and easily identifiable colour change
9
Q
What are the components of an acid base titration?
A
- Burette is filled with an alkali of known concentration (titrant)
- Titrant added to acid of unknown concentration (analyte) until the end point is reached (neutralised)
- Usually burette contains acid (both work)
10
Q
What are thermometric titrations?
A
- Heat is released when an acid and base react together (exothermic)
- Enthalpy change of neutralisation, when one mole of water is formed in the reaction of an acid and base
