Topic 4 - Chemical changes Flashcards
How do you measure the PH?
1) indicator. Indicator is a dye that changes colour depending if it’s acid or alkali
2) PH probe. pH probe is attached to a pH meter can also be used to measure pH electronically
What is a base?
A base is a substance with a pH greater than 7
What is an acid?
A substance that forms an aw solution with a pH of 7 or less
What is an alkali?
A base that dissolves in water to form a solution with a pH greater than 7.
What do alkalis form in water?
OH (minus) ions
What ions do acids form in water?
H+ ions
What is neutralisation?
The reaction between acids and bases
What does an acid + base produce?
Acid + base ——> salt + water
H+ (aq) + OH- (aq) ——> H2O (l)
Products in neutralisation are…
Beau trail so their PH is 7
What neutralisation can be used:
Neutralisation reactions of strong acids and alkalis can calculate the concentration of an acid or alkali via tritiation.
Universal indicator is used to….
Estimate the pH of a solution because it can turn into a variety of colours.
Each colour indicates a narrow range of pH values
It’s made from a mixture of different indicators. The change is gradual
Universal indicator in titrations…
Can’t be used so we use litmus because…
During titrations you want to see a sudden colour change at the end point.
So in titrations you need to use a single indicator such as litmus.
A proton is a
H+ ion
Acids produce protons in…
Water.
Acids ionise in aqueous solutions- they produce hydrogen ions, H+
HCL ——> H+ + cl-
HNO3 —-> H+ + NO3
Strong acids ionise completely in….
Water
All acid particles dissociate to release H+ ions.
Examples of strong acids: sulfuric,hydrochloric and nitric acids.
