1.8 Acids, Bases and Salts

Hazard

A danger or risk.

Explosive

It is a chemical compound, mixture or device that explode

Oxidising

Provides oxygen to make other substances burn more fiercely

(Extremely) Flammable

Capable of burning with a flame and sets fire easily

Corrosive

These substances can burn through skin, clothing and other tough materials. When spilled tell teacher immediately and start washing off. Use goggles and a lab coat

Environmental Hazard

Substances that can cause harm to the environment. Special disposal regulations

acute toxicity

These substances can cause death when breathed in, swallowed or absorbed by skin. We will not use these substances.

Gases under pressure

Gas released may be very cold. Gas container may explode if heated

Moderate hazard

A substance that may cause irritation to the skin, eyes or inside your body.

Health hazard

may cause serious health effects, for example to the respiratory tract

Risk

How likely a hazard is to cause harm

Precaution

A measure taken in advance to prevent harm

Common laboratory precautions

Using less hazardous substances, wearing eye protection, using a waterbath

Filtration

Separates insoluble solid from a liquid

Crystallisation

The formation of crystals (as solvent evaporates from solution)

Filtrate

Liquid that has passed through a filter

Residue

The insoluble solid left in the filter paper

Advantage of heating a reaction

Speeds the reaction up

Making salt from acid+base

Reacting an excess of insoluble base with an acid, filter off excess base

Making a salt from acid+metal

React an excess of metal with an acid, filter off excess metal

Making salt from acid+alkali

Use titration with an indicator to find the amount alkali to neutralise the acid, repeat without indicator to make a pure sample

Making pure dry crystals

Crystallisation then pat crystals dry between two pieces of filter paper

Advantage of a water bath

Heats gently, allowing water to evaporate slowly

Indicator

A compound that changes color in the presence of an acid or a base

Pipette

A glass or plastic tube used to accurately measure liquid

Burette

A graduated glass tube with a tap at one end, for delivering known volumes of a liquid

Making salt from an acid and an alkali

Use a titration to find the amounts of acid and alkali, repeat without indicator, evaporate water

Acid

A substance that increases the hydrogen ion concentration of a solution.

Base

A substance that reacts with an acid and neutralises it

Alkali

A soluble base, that produces OH- ions in solution

Types of chemicals that are bases

Metal oxides, metal hydroxides, metal carbonates, ammonia

Types of chemicals that are alkalis

Metal hydroxides, ammonia

Ions produced by acids

H+

Ions produced by alkalis

OH-

Neutralisation reaction

The reaction of an acid and a base forming a salt and water

Ionic equation for an acid and an alkali

H+(aq) + OH-(aq) --> H2O(l)

Strong acid

An acid that ionises completely in water

Weak acid

An acid that only partially ionises in water

Dilute

a solution containing little solute

Concentrated

large amount of solute

Standard solution

A solution of known concentration

Burette

A graduated glass tube with a tap at one end, for delivering known volumes of a liquid

Pipette

A glass or plastic tube used to accurately measure liquid

Meniscus

Curved surface of liquid

End point of titration

the point at which the indicator changes color

Indicator

A compound that changes color in the presence of an acid or a base

Titre

The volume of liquid added at the end point

Rough titre

A quick titration 'test-run' which can tell us roughly what your titre would be.

Concordant results

Titres that are within 0.10cm3 of each other

Phenolphthalein

Indicator which is clear in acidic solution and pink in basic solution.

Pipette filler

Device used to safely fill a pipette

White tile

A white surface to clearly see the indicator changing colour

Conical flask

Used to hold liquids, narrow neck to prevent splashes

pH Strong acids

0-2

pH Weak acids

3-6

pH Strong alkalis

12-14

pH

A measure of H+ concentration

pH Weak Alkali

8-10

Neutral pH

7

pH of acids

less than 7

pH of alkalis

more than 7

Universal indicator

An indicator with a different colour for each pH value

If pH decreases by 1

hydrogen ion concentration increases x10

At pH 7

concentration of H+ = concentration of OH-

Strong acid

An acid that ionises completely in water

Weak acid

An acid that only partially ionises in water

Phenolphthalein

Indicator which is clear in acidic solution and pink in basic solution.

Litmus

Indicator that turns red in acid and blue in base

Methyl orange

Indicator that is red in acid, yellow in alkali

pH probe

An instrument which measures pH to 1 decimal place