Topic 4 - Chemical changes (without electrolysis)

What is the pH scale?

A measure of how acidic or alkaline a solution is

What are the number scale of the pH scale?

0 - 14

Is a solution acidic of alkaline is it has a pH between 0 - 6?

Acidic

Where is neutral on the pH scale?

7

Is a solution acidic or alkaline if it has a pH between 8 - 14?

Alkaline

3 examples of acids?

1. Stomach acid

2. vinegar

3. lemon juice

3 examples of alkaline?

1. Bleach

2. Soap powder

3. Washing-up liquid

What is an example of neutral substances?

Pure water

How can you measure the pH of a solution?

1. Using an indicator

2. Using a pH probe attached to a pH meter

What can an acid be defined as?

An acid is a substance that forms an aqueous solution with pH less than 7 and form H⁺ ions in water

What can a base be defined as?

A base is any substance that will react with an acid to form a salt

What can an Alkali be defined as?

A base that dissolves in water to form a solution that has a pH grater than 7 and form OH^- ions in water.

What is the reaction between acids and bases called?

Neutralisation - the products are neutral - they have a pH of 7

What is the equation for the reaction between an acid and the base?

acid + base = salt + water

PLS DO TITRATION PRACTICAL FLASCARDS ON PMT?

YES OR NO?

What are strong acids?

All of the acid particles in a strong acid produce H^+ ions - they ionise completely in the water

What are weak acids?

Only a small proportion of acid particles dissociate to release H^+ ions - they don not fully ionise in the solution

Examples of strong acids?

1. Sulfuric acid

2. Hydrochloric acid

3. Nitric acids

Examples of weak acids?

1. Ethanoic acids

2. Citric acids

3. Carbonic acids

Why is the ionisation of weak acids a reversible reaction?

There is an equilibrium between the undissociated and dissociated acid

For every decrease of 1 on the pH scale…

The concentration of H^+ ions increases by a factor of 10

How to work out the H+ ion concentration using the pH?

10^-x where x = difference in pH (final pH - start pH)

Word equation for acid + Metal Oxide/Metal hydroxide and Acid + metal carbonate?

1. Acid + Metal Oxide = Salt + water

2. Acid + Metal Hydroxide = Salt + water

3. Acid + Metal Carbonate = Salt + Water + carbon dioxide

What is the reactivity series?

The reactivity series lists metals in order of their reactivity towards other substances

Order of metals in the reactivity series?

How can metals be extracted from their ores if they are less reactive than carbon?

Reduction with carbon

Which metals will not react with acids?

Metals that are less reactive than hydrogen

What is the equation when acids react with metal?

Acid + Metal = Salt + Hydrogen

How to test to confirm that hydrogen is formed in these reactions?

Use the burning splinter test:

1. Hold a burning splinter next to the test tube containing hydrogen

2. If there is hydrogen present - you will hear a squeaky pop

What is the equation when water reacts with metals?

Metal + Water = Metal + Hydroxide

Which metals won’t react with water?

1. Zinc

2. Iron

3. Copper

What are the Redox reactions?

OIL RIG:

1. A loss of electrons is called oxidation

2. A gain of electrons is called reduction

What determines how reactive a metal is?

How easily it loses electrons to form positive ions

2 examples of Redox reactions?

1. Metals reacting with acids

2. Halogen Displacement Reactions