Acids, Bases and Neutralisation

4.1, and 4.2

What are acids

Acids are species that donates proton in aqueous solution

What makes an acid strong

Strong acids completely dissociate when dissolved in water

What makes an acid weak

Weak acids partially dissociate when dissolved in water giving an equilibrium mixture

What are some common strong acids

1. HCl- hydrochloric acid

2. H₂SO₄- sulfuric acid

3. HNO₃- nitric acid

What is a base

A base readily accents a proton from an acid and neutralises the acid

What are some common bases

1. Metal oxides- MgO, CaO, CuO

2. Metal hydroxides- NaOH, KOH

3. Metal carbonates- Na₂CO_3, CaCO_3, CuCO₃

4. Ammonia- NH₃

What is an alkali

An alkali is a soluble base that releases OH^- ions in aqueous solutions

What happens in a neutralisation reaction

In a neutralisation reaction H⁺ reacts with a base to form a salt and water (and carbon dioxide if the base is a carbonate)

ACID + BASE → SALT + WATER

ACID + CARBONATE → SALT + WATER + CARBON DIOXIDE

How are alkalis used in neutralisation

ACID + ALKALI → SALT + WATER

What is the ionic equation for acid + alkali neutralisation

H⁺ + OH^- → H₂O

What is a titration

Titration is a technique used to accurately measure the volume of one solution that reacts exactly with another solution

What 3 things can a titration be used for

1. Finding concentration of a solution

2. Identifying unknown chemicals

3. Finding purity of a substance

What is a standard solution

A standard solution is a solution of known concentration

Describe the process used to make standard solution

1. Weigh the solid

2. Dissolve solid in a beaker using distilled water

3. Transfer solution to volumetric flask

4. Rinse the beaker and transfer the content to the volumetric flask

5. Fill the flask to graduation line with distilled water

6. Invert the flask several times to thoroughly mix the solution

Describe the titration procedure

1. Add acid to the burette and record the initial burette reading

2. Pipette 25cm³ of alkali into the conical flask

3. Add a few drops of indicator to the conical flask

4. Place the flask on a white tile and place the tile under the tap of the burette

5. Add acid to the alkali whilst swirling the mixture until the appropriate colour change occurs

6. Record the final burette reading

7. This is the rough titre so repeat, adding the acid dropwise when approaching the end-point

8. Repeat until concordant results are obtained

What is the titre equation

Titre = initial burette reading - final burette reading

What does concordant mean

Concordant results are within 0.1cm³ of one another