Studied by 4 peopleAcid
Acids are substances which produce H+ (aq) ions when dissolved in water.
Alkali
Alkalis are substances which produce OH- (aq) ions when dissolved in water.
Base
A base is a compound that neutralises an acid. Bases that are dissolved in water are alkalis.
When a solution has pH < 7, it is:
Acidic
When a solution has pH > 7, it is:
Alkaline
When a solution has pH = 7, it is:
Neutral
If [H+] = [OH-] then pH…
pH = 7 (neutral)
If [H+] > [OH-] then pH…
pH < 7 (acidic)
If [H+] < [OH-] then pH…
pH > 7 (alkaline)
An acidic solution will contain more _____ ions than _____ ions.
Hydrogen (H+); hydroxide (OH-)
An alkaline solution will contain more _____ ions than _____ ions.
Hydroxide (OH-); hydrogen (H+)
In neutral solutions (pH 7), the concentration of hydrogen ions is _____ to the concentration of hydroxide ions.
Equal
In water and aqueous solutions, there is an _____ between hydrogen and hydroxide ions and _____ molecules.
Equilibrium; water
Elements react with oxygen to form…
Oxides
What type of solution is formed when a non-metal oxide dissolves in water?
Non-metals form acidic solutions.
What does hydrogen (non-metal) form when it is burned to form an oxide?
Hydrogen burns to form an oxide with a pH of 7.
Some metal oxides are soluble in water. When these dissolve, they form _____ _____, which are _____.
Metal hydroxides; alkaline
Ammonia is a clear, colourless, pungent gas that dissolves in water to form _____ _____, which is an _____ solution.
Ammonium hydroxide; alkaline
The chemical equation for ammonia dissolving in water is:
NH3 + H2O → NH4OH
Explain the difference between ammonia and ammonium:
Ammonia (NH3) is a covalent molecular, while ammonium (NH4) is an ion.
Do insoluble metal hydroxides alter the pH of water?
No, insoluble metal hydroxides don’t alter the pH of water.
Which element is common to all acids?
Hydrogen (H+)
Acids have what type of bonding and why?
Acids are ionic because they can conduct electricity.
Do dilute acids conduct electricity?
Yes, dilute acids conduct electricity.
What type of particle has to be present in order for a solution to conduct electricity?
Ions must be present.
Electrolysis
The separation of ionic compounds into its elements by running an electric current through it.
In the electrolysis of an acid, what gas is produced at the negative electrode?
Hydrogen, because it has a positive charge and are therefore attracted to the negative electrode.
The ion-electron equation showing the formation of hydrogen gas is:
2H+ (aq) + 2e- → H2(g)
Explain why dry pH paper is unaffected by hydrogen chloride gas but the gas turns moist pH paper red:
Hydrogen chloride gas is a covalent molecular, so when it comes in contact with moisture the covalent bonds break to form ions.
The concentration of H+ (aq) ions _____ and the pH _____ towards _____ as an acid is diluted.
Decreases; increases; 7
The concentration of OH- (aq) ions _____ and the pH _____ towards _____ as an alkali is diluted.
Decreases; decreases; 7
What type of bonding and structure is in water?
Water is a covalent molecular.
Water is expected not to conduct electricity because it has no electrons free to move. Why can pure water conduct electricity?
There are a small number of ions present in pure water, as H2O can be broken down to H+ and OH- ions.
The equation for the dissociation of water is:
H2O (l) ⇋ H+ (aq) + OH- (aq)
Neutralisation
When a base and an acid react to form a neutral solution (water) and a salt.
The equation for neutralisation is:
Acid + alkali → salt + water
Spectator ion
An ion that is present in a reaction but is not involved.
Ionic equations can be written for:
-Neutralisation reactions
-Precipitation reactions
The equation for the reaction of acids with metal oxides is:
Acid + metal oxide → salt + water
The equation for the reaction of acids with metal carbonates is:
Acid + metal carbonate → salt + water + carbon dioxide
Note
Flashcard