3.1 Acids Flashcards
What does oxidising mean?
Provides oxygen which allows materials to burn more fiercely
What does toxic mean?
Can cause death by being swallowed, inhaled or absorbed through the skin
What does highly flammable mean?
Catches fire easily
What does an environmental hazard mean?
Harmful to organisms and to the environment
What does harmful mean?
Can cause irritation, reddening or blistering of the skin
What does corrosive mean?
Destroys material , including living tissues
Safety precautions for acids
Wear eye goggles, dilute the acid with water
Acid
A substance with a pH less than 7
What will acids dissociate into in water
H+ ions
What will alkalis dissociate into in water
OH- ions
Base
A substance that neutralises an acid
Alkali
A soluble base
What colour is pH 1 on the universal indicator
Red
What colour is pH 14 on the universal indicator
Purple
What colour is pH 7 on the universal indicator
Green
What colour is litmus in acid
Red
What colour is litmus in neutral
Purple
What colour is litmus in alkali
Blue
What colour is methyl orange in acid
Red
What colour is methyl orange in neutral
Yellow
What colour is methyl orange in alkali
Yellow
What colour is phenolphthalein in acid
Colourless
What colour is phenolphthalein in neutral
Colourless
What colour is phenolphthalein in alkali
Pink
Neutralisation equation
Acid + base -> salt + water
What does pH measure?
The concentration of H+ or OH- ions
What will happen to an acid in water
It will dissociate and lose its H+ ion
Strong acid
Will fully dissociate in water
Weak acid
Will partially dissociate in water
How much will the concentration of acid increase by if the pH decreases by 1
A factor of 10
Which salt ending will products of hydrochloric acid have
Chloride
Which salt ending will products of nitric acid have
Nitrate
Which salt ending will products of sulfuric acid have
Sulfate
Which salt ending will products of phosphoric acid have
Phosphate
What is the equation for reacting an acid with a metal
Acid + metal -> salt + hydrogen
What is the test for hydrogen
Will make a squeaky pop with a little splint
What is the equation for reacting an acid with a metal carbonate
Acid + metal carbonate -> salt + water + carbon dioxide
Test for carbon dioxide
Bubble the gas through limewater and see if it goes cloudy
What will a graph look like if the x axis is the amount of base added and the y axis is the pH
There will be a small slope upwards until a rapid jump where the acid is neutralised
Hydrochloric acid
HCl
Sulfuric Acid
H2SO4
Nitric Acid
HNO3
Common soluble salt compounds
Salts of sodium, potassium and ammonium
Which nitrates are soluble
All of them
Which nitrates are insoluble
None of them
Which chlorides are insoluble
Silver chloride and lead chloride
Which chlorides are soluble
Most of them
Which sulfates are insoluble
Lead sulfate, barium sulfate and calcium sulfate
Which sulfates are soluble
Most of them
Which carbonates and hydroxides are soluble
Sodium, potassium and ammonium
Which carbonates and hydroxides are insoluble
Most of them
How to make insoluble salts from two soluble salts
- Add the two soluble salts into separate tests tubes of deionised water
- Tip the two solutions into a beaker (the insoluble salt should precipitate out)
- Filter into a conical flask
- Rinse the contents of the filter paper with deionised water
- Leave the insoluble salt to dry
Why is deionised water added to the making insoluble salts experiment
So that there are no other ions about
Improvements to the making insoluble salts experiment
Use deionised water, stir the beaker when the solutions are added, swill put the beaker with deionised water during filtration
How to make a soluble salt from an acid and an insoluble base
- Heat the acid in a water bath
- Add base until the base is in excess
- Filter off the excess solid
- Heat the solution using a Bunsen burner
- Leave the solution to cool and crystallise
Why is the solution heated at the start in the making soluble salts with an acid and insoluble base experiment
To speed up the reaction between the acid and base
What does the solution contain after being filtered in the making soluble salts with an acid and insoluble base experiment?
Salt and water
When does neutralisation occur in the making soluble salts with an acid and insoluble base experiment
When the base is in excess
Why is the salt and water heated near the end in the making soluble salts with an acid and insoluble base
So that the water evaporates
How to make a soluble salt from an acid and an alkali
- Measure a recorded amount of acid into a conical flask
- Add a few drops of indicator
- Slowly add alkali using a burette until the indicator changes colour
- Record the volume of alkali it took to neutralise
- Repeat the experiment with the same volumes but no indicator
- Heat up the solution
- Leave it to crystallise
Why shouldn’t universal indicator be used in the making soluble salts from an acid and alkali experiment
The change in colour is too gradual
Why can’t you add excess alkali to the solution in the making soluble salts from an acid and alkali experiment
The solution will be contaminated with the excess alkali
At what point is the solution neutralised in the making soluble salts from an acid and alkali experiment
As soon as the indicator changes colour
Why is the experiment repeated without the indicator in the making soluble salts from an acid and alkali experiment
The indicator won’t contaminate the solution
Why is the solution heated at the end of the making soluble salts from an acid and alkali experiment
To evaporate the water
