D. Crowley, 2008

Acid & Alkali Hazards

Acid & Alkali HazardsTo know the hazards involved when using acids and alkalis

Wednesday, April 19, 2023

Dangers There are lots of acids and alkalis in the home that are relatively safe,

however in the laboratory we sometimes use much more dangerous chemicals…

How can you tell which chemicals are safe, and which are dangerous?

Hazard symbols are used on bottles (and vehicles) that contain hazardous chemicals – they can be identified by anyone, regardless of language

i h

Dangers

i

h

Toxic – can cause death is swallowed/inhaled/absorbed by skin etc…

Irritant – will make skin red or blister

Harmful – similar to toxic, but not quite as dangerous

Corrosive – attacks and destroys living tissue

Highly flammable – catches fire easily

Dangers Hazard symbols show us why the chemical is dangerous…

i h

Toxic Irritant Harmful Corrosive

Highly flamma

ble Before we carry out any experiment, we must complete

a risk assessment – we need to think about what risks there are, and what we should do if the risk occurs…

Risks Today you are going to carry

out an experiment investigating household substances, identifying if it is an acid or alkali, as well as the pH of the substance (using UI)

Complete a risk assessment for the practical (consider the risks, how we can minimise them, and what to do if they occur)

Risks Sensible laboratory behaviour as always (no running) Hair tied back No eating, and washing hands after experiment has completed

Depending on strength of acid/alkali this could be an irritant/harmful (blistering of skin) or even corrosive (destroys skin) if there is contact

Goggles to be on at all times and hands to be washed immediately if acid/alkali touches skin

In the event of a spillage do not try to clear it up, instead inform me immediatly

Experiment Test a variety of household substances, identifying if they are

an acid or alkali, and what their strength is (pH) - record your results in a table

Substance Acid or Alkali pH

Substance 1

Substance 2

Etc…

NeutralStrong acid Weak acid Weak alkali Strong alkali

Acid & Alkali Examples

NeutralStrong acid Weak acid Weak alkali Strong alkali

Stomach acid

Skin

Lemon juice

Fizzy drinks

Vinegar

Milk

Pure wate

rBlood

Indigestion

tabletsToothpas

te

Washing powder

Oven cleaner

Not hazardous Why is it that lemonade is not considered hazardous,

even though it contains lemon juice which has a pH of ~2?

Although lemon juice has a low pH it is not concentrated enough in lemonade to make it dangerous – although lemon juice on its own will still sting if it gets in a cut

The concentration of lemon juice in lemonade is very low (water has been added to it, which increases the overall pH closer to neutral) which is why we can drink it!

Hazard Symbols