Flashcards in Topic 3 - Chemical Changes Deck (22):
What are the 5 pH indicators?
What is an acid?
a substance with a pH less than 7 and containing H+ ions
What is a base?
a substance that reacts with an acid to form salt and water
What is an alkali?
A substance with a pH bigger than 7 and containing OH- ions
What does the litmus paper look like when the solution is acidic, alkali and neutral?
Acidic = red
Neutral = purple
Alkali = blue
What does methyl orange look when solution is alkali,neutral and acidic ?
Acidic = red
Neutral = yellow
Alkali = yellow
What colour does phenolphalein turn to when in acidic and alkali solutions?
Acidic = colourless
Alkali = pink
Neutral = colourless
What does the reaction between an acid and a base called? And what is the equation ?
acid + base = salt + water
Example of a neutralisation equation ?
H+ + OH- = H2O
TRUE OR FALSE
all acids can ionise/dissociate in solution.
What is ionisation/ dissociation ?
Splitting up a substance to produce H+ and another ion .
Example of ionisation
HNO3 = H+ + NO3-
What is a STRONG ACID?
Acid that ionises almost completely in solution. They tend to have a very low pH.
What is a weak acid ? What is their usual pH?
Acid that doesn’t fully ionise, their pH is around 2-6.
Example of a strong acid.
Example of a weak acid.
Name 2 differences between a strong and a weak acid.
When weak acid is ionised the process can be reversed, unlike strong acids.
Higher pH with weaker acids
Step ionises almost completely, weak only partially
What is the concentration of an acid?
Measure of how much acid there is per 1 dm3 of water. Basically how watered down your acid is.
The more acid molecules compared to the volume of solution there is the higher concentration of the acid is present
How can the pH be increased ?
By decreasing the concentration of H+ using a factor of 10.
To go down by 2pH the concentration needs to decrease by a factor of 100 (10x10)
How can the pH can decreased?
It can be decreased by increasing the H+ ion concentration by a factor of 10.
Salt is a what type of compound ?
An ionic compound.