Module 2: Chapter 4 (Acids and redox)
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What are the formula of 4 common acids?
hydrochloric acid -> HCl sulphuric acid -> H2SO4 nitric acid -> HNO3 ethanoic acid -> CH3COOH
What are the formulae of 3 common alkalis?
sodium hydroxide -> NaOH potassium hydroxide -> KOH ammonia -> NH3
What are acids?
when dissolved in water an acid releases H+ ions into the solution (dissociation)
What is the difference between a strong acid and a weak acid?
• a strong acid completely dissociates in water (HCl, HNO3, H2SO4) • for a weak acid dissociation is incomplete, written as an equilibrium (carboxylic acid)
What is the ethanoate ion?
CH3COO-
What is a base?
• metal oxides, metal hydroxides, metal carbonates and ammonia are all classified as bases • a base neutralises an acid to form a salt
What is an alkali?
an alkali is a base that dissolves in water releasing hydroxide ions
State the 4 general reactions involving acids
• acid + alkali -> salt + water • acid + metal oxide -> salt + water • acid + carbonate -> salt + water + CO2 • acid + ammonia -> ammonium salt
How do you prepare a standard solution in an acid-based titration?
• solid is weighed accurately • solid dissolves in a beaker with distilled water, less than what is needed to fill flask • solution is transferred to a volumetric flask (traces are rinsed with distilled water into the flask) • flask filled to the graduation line by adding distilled water a drop at a time until the bottom of the meniscus lines up exactly at eye level (if over solution must be prepared again) • flask slowly inverted many times to mix solution thoroughly (if not done titration results will be inconsistent)
What are the 3 steps for titration calculations?
• work out the amount, in mol, of the solute in the solution for which you know both the concentration and volume • use the equation to work out , in mol, of the solute in the other solution • work out the unknown information about eh solute in the other solution
Oxidation Rules: simple ions
oxidation number is just the charge on the ion
Oxidation Rules: elements
oxidation number for elements not in a compound is zero
Oxidation Rules: fluorine
ALWAYS -1
Oxidation Rules: oxygen
-2, unless bonded to F or in a peroxide like H2O2
Oxidation Rules: chlorine
-1, unless bonded to F or O
Oxidation Rules: bromine
-1, unless bonded to F, O or Cl
Oxidation Rules: iodine
-1, unless bonded to F, O, Cl or Br
Oxidation Rules: hydrogen
+1, unless it’s present as a hydride ion
Oxidation Rules: group 1 or group 2 metals
group 1 or 2 metals will always be present ions in their compounds so will be +1 and +2
Oxidation Rules: compounds
oxidation number of each atom must add up to the charge of the compound
Oxidation Rules: sign
sign is put BEFORE the oxidation number, unlike charges
What is meant by oxidation?
oxidation is the loss of electrons or increase in oxidation number
What is meant by reduction?
reduction is gain of electrons or decrease in oxidation number
What is the oxidising agent?
takes electrons from the species being oxidised - therefore contains the species that is reduced