Topic 2: Acids, Bases and Salts Flashcards
If a substance has a pH of 0, what is it?
A very strong acid.
If a substance has a pH of 7, what is it?
Neutral
If a substance has a pH of 14, what is it?
A very strong alkali.
What ions do acids contain?
H⁺ ions.
What ions do alkalis contain?
OH⁻ ions.
What does it mean if an acid/alkali is dilute?
There are more water molecules mixed with the H⁺/OH⁻ ions.
What does it mean if an acid/alkali is concentrated?
There are fewer water molecules mixed with the H⁺/OH⁻ ions.
What is the reactivity series?
Potassium Sodium Calcium Magnesium Aluminium Zinc Iron Tin Lead Copper Silver Gold
What are the 3 acids used for reactions?
at gcse level
Hydrochloric acid
Sulfuric acid
Nitric acid
What is the symbol of hydrochloric acid?
HCl
What is the symbol of sulfuric acid?
H₂SO₄
What is symbol of nitric acid?
2HNO₃
What is the word equation for metals reacting with acids?
metal + acid ➜ metal salt + hydrogen
example: magnesium + hydrochloric acid ➜ magnesium chloride + hydrogen
What is the word equation for bases/alkalis reacting with acids?
acid + base/alkali ➜ metal salt + water
example: hydrochloric acid + calcium oxide ➜ calcium chloride + water
What is the chemical test for carbon dioxide gas?
Pass carbon dioxide (by blowing) through limewater (calcium hydroxide solution). If the gas is carbon dioxide then the limewater turns cloudy.
What is the test for a carbonate?
When acid reacts with a carbonate, fizzing is observed. Bubbles are seen, as CO2 is a gas.
What is a carbonate?
A carbonate is an ion consisting of one carbon and three oxygen atoms.
What is the word equation for a reaction with a carbonate?
acid + metal carbonate ➜ metal salt + water + carbon dioxide
(example: sulfuric acid + magnesium carbonate ➜ magnesium sulfate + water + carbon dioxide)
What is the difference between an alkali and a base?
An alkali is a base that can dissolve in water.
Metal oxides are known as bases.
Metal hydroxides are known as alkalis.
What happens in a neutralisation reaction?
H⁺ and OH⁻ ions react together to create water.
example: hydrochloric acid + sodium hydroxide → sodium chloride + water
When an acid reacts with a metal, is the reaction endothermic or exothermic?
Exothermic.
How do you test for hydrogen?
Hydrogen causes bubbling during a reaction. It can be detected using a lighted splint, which causes the gas to burn with a squeaky pop.
When an acid reacts with a base, is the reaction endothermic or exothermic?
Exothermic.
When an acid reacts with an alkali, is the reaction endothermic or exothermic?
Exothermic.
When an acid reacts with a carbonate, is the reaction endothermic or exothermic? And are there any other clear reactions?
Exothermic and fizzing.
What is the test for sulfate ions?
When adding barium chloride to the solution, a white precipitate is formed.
What is the test for oxygen?
Oxygen will re-light a glowing splint.
What is dissociation?
A general process in which molecules or ionic compounds split or separate into smaller particles such as atoms or ions.
Which will dissociate better, a strong or weak acid?
A strong acid. All the H⁺ ions would dissociate fully.
Which will dissociate better, a strong or weak alkali?
A strong alkali. All the OH⁻ ions will dissociate fully.
Why is the rate of reaction is higher in strong acids/alkalis in comparison to weak ones.
As strong acids/alkalis dissociate quicker, the rate of reaction is higher and so is the temperature rise.
What is a precipitate?
An insoluble solid, formed when 2 or more solutions are mixed.
What is the ionic equation for testing sulfate ions?
Ba²⁺+(aq)+ SO₄²⁻(aq) ➜ BaSO4(s)
What is the ionic equation for a acid and alkali reaction?
H⁺(aq) + OH⁻(aq) → H₂O(l)
What is a salt?
Any compound formed by neutralisation of an acid by a base, when some or all the hydrogen ions in an acid are replaced by metal ions.
What happens when ammonium reacts with acids?
Ammonium salts form.
For instance, ammonia reacts with hydrochloric acid to make ammonium chloride.
What is the ‘excess’ in preparation of salts?
The left over insoluble solute that won’t dissolve.
Why is filter paper used in preparation of salts?
To separate the insoluble excess from the salt solution.
How are salts extracted from a salt solution?
By evaporation. Firstly, you heat the solution on a Bunsen burner until 1/3 of the solution remains then leave to evaporate naturally.
How do you gain larger crystals in preparation of salts?
By allowing the salt solution to evaporate naturally instead of using heat to speed the process.
What is titration used to find out?
The unknown concentration of an alkali/acid.
What are the 4 pieces of equipment needed for titration?
pipette
pipette filler
conical flask
burette
What is the 6 point method of titration? (acid added to alkali for this example)
- . Use the pipette and pipette filler to add 25 cm³ of alkali to a clean conical flask.
- Add a few drops of indicator and put the conical flask on a white tile.
- Fill the burette with acid and note the starting volume.
- Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix.
- Stop adding the acid when there is colour change. Note the final volume reading.
- Repeat steps one to five using the same volume of acid from the burette without using an indicator. The resulting solution can then be evaporated to obtain pure crystals of the salt.
How is a precipitate reaction carried out?
2 soluble salts react to create an insoluble salt.
How do you calculate the number of moles in a solution?
number of moles = concentration (mol/ dm³) x volume (dm³)
How do you calculate the concentration in g/ dm³?
mol / dm³ x relative formula mass of acid = g / dm³
