4 ACIDS, BASES AND SALTS Flashcards
what do acids produce when dissolved in water
the H+ ions split from the acids
eg. HCl -> H+(aq) and Cl−(aq)
Definition of acid
An acid is a substance in which its molecules dissociates in water to produce H + (aq) ions
some non liquid form of acid such as vitamin c tabs(absorbic acid) or hydrogen chloride gas(HCL) will have no effect on dry blue litmus paper. explain y
the acid does not ionize into h+ ions and ?? ions in the absence of water
what is the basicity of an acid
The basicity of an acid is the number of ionizable hydrogen ions that can be produced by a molecule of the acid. (dissociate)
what are monobasic acids
1 molecule of the acid yields 1 H+ ion when dissociated.
what are dibasic acids
1 molecule of the acid yields 2 H+ ions when dissociated.
what are tribasic acids
1 molecule of the acid yields 3 H+ ions when dissociated.
strong acid definition
A strong acid is one in which its molecules dissociate completely in water to give a high concentration of hydrogen ions (H+).
3 strong acids
H2SO4
HNO3
HCL
weak acid definition
A weak acid is one in which its molecules dissociate partially in water to give a low concentration of hydrogen ions (H+).
2 weak acids
CH3COOH
H2CO3
what is a dilute acid solution
An acid solution that contains a small amount of the dissolved acid is said to be dilute.
what is a concentrated acid solution
An acid solution that contains a large amount of the dissolved acid is said to be concentrated.
how to calculate concentration using pH
pH = – lg[H+]
concentration vs strength
concentration : small amount of acid dissolved per unit volume of water.
strength : whether acid dissociate completely (strong acid) or partially (weak acid).
4 properties of acid
- Acids have a sour taste
- Acids dissolve in water to form solutions which conduct electricity.
- Acids turn blue litmus paper –> red.
- Acids react with reactive metals to form hydrogen gas and a salt.
reactivity series of metals
Kangaroos normally can’t make a crocodile zesty, for some prefer hopping closely around a pond.
potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, tin, lead, hydrogen, copper, silver, gold, platinum
how to use the reactivity series
Metals above hydrogen in the reactivity series react with acids to form hydrogen and salt.
- Metals below carbon can be extracted from their oxide
using carbon. Eg. 2ZnO + C → 2Zn + CO2 - Metals below hydrogen can be extracted from their oxide
using hydrogen gas. Eg. 2CuO + H2 → 2Cu + 2H2O
some salts have specific names when reacting with their corresponding acids
**chlorides* when they are formed from hydrochloric acid;
nitrates when formed from nitric acid;
sulfates when formed from sulfuric acid.
definition of salt
A salt is the ionic compound formed when hydrogen ions from an acid are displaced by metal or ammonium ions.
The anion of salt comes from an acid.
The cation comes from the base
HCl + NaOH → NaCl + H₂O
how to test for hydrogen gas
place the lighted splint at the mouth of the reaction test tube. If the lighted splint extinguishes with a “pop” sound, hydrgoen gas is produced
metal + acid?
salt + hydrogen
metal + carbonate
salt + water + carbon dioxide
how to test for carbon dioxide
Bubble the gas through a test tube of limewater using a delivery tube. If a white precipitate is formed with limewater, carbon dioxide gas is produced.
CO2 (g) + Ca(OH)2 (aq) → CaCO3 (s) + H2O (l)
metal hydroxide/oxide + acid?
→ salt + water (NOT hydrogen)
oxide: ZnO (s) + H2SO4 (aq) → ZnSO4 (aq) + H2O (l)
hydroxide: NaOH (aq) + HCl (aq) → NaCl (aq) + H2O (l)
if u think abt it the extra Os from the oxide and hoxide js makes the hydrogen into water.
definition of neutralisation
Neutralisation is the combination of hydrogen ions from an acid with the hydroxide ions from an alkali or base to form water molecules and salt as the only products.
definition of a base
A base is a substance that dissociates in water to produce OH─
ions.
Bases which are soluble in water are known as ?
alkalis
strong alkali definition
A strong base/alkali is a substance that dissociates completely in water to give a high concentration of hydroxide ions (OH─).
i.e. complete dissociation, eg. KOH (aq) → K+(aq) + OH─(aq)
weak alkali definition
A weak base/alkali is a substance that dissociates partiallly in water to give a low concentration of hydroxide ions (OH─).
i.e. partial dissociation, eg. NH3 (aq) + H2O (l) ⇌ NH4+(aq) + OH─(aq)
what is the acidity of a base
The acidity of a base is the number of ionizable hydroxide ions that can be produced by a formula unit of the base.
what is monoacidic base
For monoacidic base, 1 formula unit of the alkali yields 1 OH─ ion when dissociated.
what is diacidic base
For diacidic base, 1 formula unit of the alkali yields 2 OH─ ions when dissociated.
properties of alkali
- Alkalis have a bitter taste and soapy feel.
- Alkalis turn red litmus paper blue.
- All alkalis produce hydroxide ions when dissolved in water.
how to do an ionic equation
- balanced equation
NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l) - pop the ions
Na+(aq) + OH−(aq) + H+(aq) + Cl−(aq)
→
Na +(aq) + Cl−(aq) + H2O(l) - erase the spectator ions(same on both sides)
Na +(aq) + Cl−(aq) r on both sides - final ionic eq
OH−(aq) + H+(aq) → H2O(l)
**only (aq) can be split, solids,liquids,gas cant be split(eg. h2o)
alkali + ammonium salt + ??
+ HEATING
→ ammonia + water + salt
how to test for ammonia gas
If a colourless, pungent gas that turns damp red litmus paper blue is produced, gas is ammonia.
how to use pH to test for acidity or alkalinity
7 is neutral, or pure water at 25C.
acidity 0-6
alkalinity 8-14
lower means more h+ ions
does pH test for strength of an acid?
no. pH is a measure of the (total) concentration of H+ in a solution. It is not a measure of the strength of the acid unless the two acids being compared have the same initial concentration.
what is pOH
essentially its the opposite to pH, like ying yang. lower the pH higher the pOH on a 14 scale. pH + pOH = 14
HOW TO SOLVE pH = – lg[H+/OH-] QNS
its probably gonna be a strong acid or base cuz they havent taught us otherwise. since they fully dissociate so to get h or or oh ions its always the concentration x ONE. then js multiply it by how many h or oh ions there are in the acid or base
0.10 mol dm–3 of Ca(OH)2(aq)(strong base)
theres 2 OH, so 0.10 x 2
pOH = –lg 0.2 = 0.699
universal indicator colours
red, orange, yellow, green, blue, purple
3 2 2 2 3 3
methyl orange colours
red orange yellow
acid neutral alkaline
Phenolphthalein colours
colourless pale pink pink
acid neutral alkaline
Thymolphthalein colours
colourless pale blue blue
acid neutral alkaline
what are acidic oxides
Acidic oxides are oxides of non-metals. Most acidic oxides dissolve in water to form an acid.
Carbon dioxide CO2 -> carbonic acid
Sulfur dioxide SO2 -> sulfurous acid
Sulfur trioxide SO3 -> sulfuric acid
Phosphorus(V) oxide P4O10 -> phosphurus acid
Acidic oxides react with alkalis to form a salt and water, just like acids.
what are basic oxides
The oxides of metals are basic oxides. Most basic oxides are insoluble in water,
except for a few which dissolves readily in water and are called alkalis.
* Basic oxides are solids at room temperature.
* They react with acids to form a salt and water, just like alkalis.
how to use solubility rules
when something is soluble it dissolves, if not its insoluble it forms a precipitate
what are Amphoteric Oxides
Amphoteric oxides are metallic oxides that react with both acids and bases to form salts and water.
Aluminium oxide Al2O3
Lead(II) oxide PbO
Zinc oxide ZnO
Thus, in reaction with acids, amphoteric oxides behave as a basic oxide.
However in reaction with alkalis, amphoteric oxides behave like an acidic oxide.
what are Neutral Oxide
Some non-metal oxides show neither basic nor acidic properties and are thus referred to as neutral oxides. Neutral oxides are insoluble in water.
water H2O
carbon monoxide CO
nitric oxide NO
solubility rules
SPAN : sodium, potassium, ammonium, nitrates soluble
BACALs :(barium calcium lead) sulfates insoluble
LEASIL17 :all halides(grp17 chlorides) soluble UNLESS paired with lead and silver
SPAc :All carbonates are insoluble except Na+, K+ and NH4+
SPoh: All hydroxides/oxides are insoluble except Na+, K+ and Ba2+.
where acids are sulfites and sulfates derived from
sulfites : sulfurous acid H2SO3
sulfates : sulfuric acid H2SO4
whats an acid salt
when not all hydrogen ions of an acid are replaced by metallic ions
Acid : H2CO3 : carbonic acid
— Partial replacement : Acid Salt : NaHCO3
Sodium hydrogencarbonate
— Full replacement : Normal salt : Na2CO3
Sodium carbonate
what is water of crystallisation
Many salts combine with water molecules to form crystals. These water molecules are known as water of crystallization. Salts that contain water of crystallization are known as hydrated salts, whereas those that do not contain water of crystallization are known as anhydrous salts.
Name of Salt — Anhydrous salt — Hydrated salt
Sodium carbonate — Na2CO3 — Na2CO3.10H2O
Copper (II) sulfate — CuSO4 — CuSO4.5H2O
Zinc sulfate — ZnSO4 — ZnSO4.7H2O
Magnesium sulfate — MgSO4 — MgSO4.7H2O
When a hydrated salt is heated, its water of crystallization is driven off and the anhydrous salt is formed.
how to prepare insoluble salts using the precipitation method
mix a soluble salt (e.g. a nitrate salt) that contains its cations* (positive ions)
with a soluble salt (e.g. a sodium salt) that contains its anions (negative ions).
STEPS
* Add an excess of ONE solution to the other and stir thoroughly until no more ppt forms.
* Filter the liquid to separate the precipitate. The filtrate can be discarded.
* The residue is then washed with deionized water to remove unwanted reactants.
* Dry the crystals by pressing between a few sheets of filter paper.
Preparation of Soluble Salts (not containing Group 1 or ammonium cations) using an insoluble
reactant [Filtration Method]
- Add excess insoluble (metal / base / carbonate) to warm dilute acid and stir until no more reacts. (ensure all acid gets reacted)
- Filter the mixture to obtain the filtrate.
- do crystalisation: heat filtrate till saturation, test for saturation, cool it till crystals
- Filter to obtain the crystals.
- wash WITH A SMALL AMT OF COLD deionized water
- dry crystals between filter paper
** a test for saturation can be conducted by dipping a glass rod into the concentrated filtrate. If crystals form on the cool rod, the solution is saturated and no further heating is required.
what metals cant be put into acid
- Unreactive metals such as lead and copper as these metals do not react with dilute acids, they form a layer of insoluble salt
- Very reactive metals such as sodium, potassium and calcium as the reaction is too vigorous.
Preparation of Soluble Salts (containing Group 1 or ammonium cations) using a soluble reactant (e.g.
an alkali)
titration method.
** acid and alkaline r interchangeable
- Pipette 25.0 cm3 of alkaline solution into a conical flask.
- add 2-3 drops of indicator, perhaps universal
- have a burette loaded with acid, its initial volume is v1
- slowly drop acid in until 1 drop change sthe indicator
- remaining voplume in burette is v2
v1 - v2 = v3 how much acid it takes to complete neutralization
now add v3 into the alkaline w/o the indicator cuz its impure,
crystalize it and its soluble salts
