Acids and Alkalis Flashcards
What is an acid?
A substance with a pH less than 7
What is an alkali?
A substance with a pH more than 7
What do we called something that changes colour depending on whether it is an acid or an alkali?
Indicator
Universal indicator is an indicator which is commonly used in the lab
What colour does universal indicator go in a strong alkali?
purple
What colour does universal indicator go in a weak alkali?
blue
What colour does universal indicator go in a weak acid?
yellow/orange
What colour does universal indicator go in a strong acid?
red
Give an example of a neutral substance
pure water
common salt (sodium chloride)
How can you test the pH of a substance?
Use a indicator which is a substance which will change colour depending on whether it is put in an acid or an alkali
Use a pH meter which will give a number value of the pH
A pH meter will give you a more accurate measurement than an indicator
What is the pH of a neutral substance?
7
What two things are made when an acid reacts with an alkali?
Salt and water
What is a neutralization reaction?
When an acid reacts with an alkali to make a salt and water
It is known as a neutralization reaction because the salt and water have a neutral pH
What is the pH scale?
A coloured number scale that goes from 0 to 14.
It tells you how acidic or alkaline a substance is
Where are alkalis often found?
In cleaning products such as soap, washing up liquid, toothpaste, drain cleaner
How do you get the salt out of the water?
Let the water evaporate to leave the salt behind.
The solution is often put in an evaporating dish.
Salts have a two-part name.
The first part comes from the alkali.
The second part comes from the acid.
Nitric acid always produces salts that end in nitrate.
Sulfuric acid always produces salts that end in sulfate.
Hydrochloric acid always produces salts that end in chloride.
What is a dilute acid?
An acid with lots of water in it
What is a concentrated acid?
An acid that has very little water in it
what is the pH of a strong alkali?
13-14
what is the pH of a weak acid?
4-6
what is the pH of a strong acid?
1-3
Weak acids are often found in food.
How do weak acids taste?
bitter
