Chemistry GCSE Acids and Alkalis Flashcards
What colour will litmus solution be in an acid?
red
What colour will litmus solution be in an alkali?
purple/blue
What colour will litmus solution be in a neutral substance?
purple
What colour will phenolphthalein be in an acid?
colourless
What colour will phenolphthalein be in an alkali?
pink
What colour will phenolphthalein be in a neutral substance?
colourless
What colour will methyl orange be in an acid?
pinkish red
What colour will methyl orange be in an a neutral substance?
orange
What colour will methyl orange be in an alkali?
yellow
What colour will methyl orange be in an alkali?
yellow
What colour will universal indicator be in an acid?
red/orange
What colour will UI be in an alkali?
purple/blue
What colour will UI be in a neutral substance?
green
How do litmus papers change in different pHs?
red litmus paper turns blue in an alkali, and vice-versa
What causes acidity?
the H+ ion
What is the pH scale?
A measure of the concentration of H+ ions in a solution, and hence its acidity.
What does pH stand for?
p- potenz, german word for power
H- (hydrogen)
what type of scale is the pH scale?
logarithmic
how many more times the amount of hydrogen does a pH-1 acid have than a pH-2 acid?
ten times
What is the name of the equipment you can use to measure a substance’s pH?
a pH probe or pH meter
How are solutions of acids made?
specific covalent molecules dissolved in water,which causes the molecules to break apart, generating hydrogen ions
What do the words concentrated and dilute refer to, in terms of acids?
The amount of acid molecules dissolved in water. A concentrated acid will have a large amount of acid molecules dissolved in a certain amount of water, and vice-versa
What do the words strong and weak refer to, in terms of acids?
The amount of the acid molecules that have been split apart into ions.
What is dissociation?
acid molecules splitting into ions
What is ionisation?
acid molecules splitting to ions
What is another word for dissociation?
ionisation
What makes an acid a strong one?
It will completely dissociate into ions in water- all of the molecules will have broken apart to form hydrogen ions.
Give some examples of strong acids
Hydrochloric acid, nitric acid and sulphuric acid
What makes an acid a weak one?
Only a small proportion of the molecules will have dissociated into ions. The solution mostly contains undissociated molecules, and a low number of ions
Give an example of a weak acid
ethanoic acid
What is the formula for ethanoic acid?
CH₃COOH
What is a base?
A substance that can neutralise an acid, soluble or not
What is an alkali?
A soluble base/a substance that releases OH- ions when dissolved
what causes alkalinity?
the OH- ion
Give some examples of strong alkalis
Sodium hydroxide and potassium hydroxide
Give an example of a weak alkali
ammonia
What is the product of a reaction between a reactive metal and an acid?
metal salt + hydrogen
What is the product of a reaction between a base and an acid?
metal salt + water
What is the product of a reaction between a metal carbonate and an acid?
metal salt + water + CO2
What is the product of a reaction between ammonia and an acid?
an ammonium salt
if the end result of a reaction was an ammonium salt, what were the reactants?
ammonia + an acid
if the end result of a reaction was a metal salt and hydrogen, what were the reactants
reactive metal + acid
if the end result of a reaction was water and a metal salt, what were the reactants?
base + acid
give four examples of non reactive metals
Gold, silver, platinum, copper
How do you write an ionic equation?
1) write balanced equation
2) rewrite equation separating out ions in the compounds and the acid. covalent compounds stay unseparated
3)cancel ions that appear on either side
4)write the ionic equation
What is the name of the ion that you remove to make an ionic equation?
spectator ion
How do you do the excess base method?
add excess base 2 acid
filter out insoluble base
heat the filtrate to evaporate most but not all water, you do not want it to be anhydrous
When do you use the excess base method?
When the base is insoluble, and the salt is soluble
When should you use titration?
When you start with an alkali and finish with a soluble salt
When should you use precipitation?
When you start with an alkali and finish with an insoluble salt
What is titration?
When two solutions are carefully mixed to determine the exact volumes of each which react together
What do you call the moment in titration when the reaction is complete?
the end-point
What equipment do you need for titration?
(among other things) a pipette and a burette
What are the solubility rules surrounding sodium salts?
All are soluble
What are the solubility rules surrounding potassium salts?
All are soluble
What are the solubility rules surrounding ammonium salts?
All are soluble
What are the solubility rules surrounding nitrates?
All are soluble
What are the solubility rules surrounding carbonates?
All are insoluble, except group 1 + NH4
What are the solubility rules surrounding hydroxides?
All are insoluble, except group 1+ NH4
What are the solubility rules surrounding chlorides?
All are soluble except silver and lead
What are the solubility rules surrounding sulphates?
All are soluble, except barium, lead and calcium sulphates
What is an acid?
A substance that releases H+ ions when dissolved in water
Why should potassium sulphate not be made from the reaction between potassium and sulphuric acid?
As a group 1 metal, potassium is highly reactive so such a reaction would be dangerous
Why could copper sulfate not be made from a reaction between copper and sulphuric acid?
Copper is not reactive enough
Give a detailed method for making a pure sample of the salt nickel chloride frim nickel oxide (insoluble base) (Four marks)
-Add HCl to NiO
-Add excess NiO
-Filter off NiO
-Evaporate water
why do you use a burette in titration? (2 points)
it is an accurate way to measure a substance which measures variable volumes- you don’t know how much it will be
in titration, you repeat until you have…
concordant results
