Chemistry - acids and bases

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Acids and bases

acid - a species which produces hydrogen ions as protons, H+, in solution. it is a proton donator

Hydrochloric acid - HCl

Sulphuric acid - H2SO4

Nitric acid - HNO3

Ethanoic acid - CH3COOH

strong acid - completely dissociates in an aqueous solution; releases all of its hydrogen atoms into solution as H+ ions

weak acid - partially dissociates in an aqueous solution; releases only a small proportion of its hydrogen atoms and H+ ions

examples of bases - metal oxides, metal hydroxides, metal carbonates and ammonia are all bases (substances that neutralise an acid to form a salt-proton acceptor)

alkali - a soluble base that will release hydroxide ions, OH-, when dissolved in water

Sodium hydroxide - NaOH

Potassium hydroxide - KOH

Ammonia - NH3

neutralisation - when H+ (aq) ions form an acid with a base to form a salt and water > during the reaction the H+ ions from the acid are replaced by metal ions or ammonium ions; a salt is made up of a metal and nonmetal (a metal bonded to part of an acid)

neutralisation reactions:

1) acid + metal hydroxide > salt + water

2) acid + metal oxide > salt + water

3) acid + metal carbonate > salt + water + carbon dioxide

Atom economy:

- measures how well the atoms of the reactants have been put to use (assumes 100% yield)

- products which are not desired and have to be disposed of are called waste products

- products which are called waste products but can be sold or utilised elsewhere are called by products

how to improve atom economy:

- improve efficiency of a process

- reduces waste

- preserves raw materials

this increases the sustainability of the process

standard solutions - a solution of a known concentration

- prepared using a volumetric flask as it makes up a standard solution very accurately (it measures volume very precisely)

- different volumetric flasks have different tolerances e.g. 100 cm3 +/- 0.20 cm3

Titrations - a technique used to measure the volume of one solution that reacts with another

used to:

- check purity of a substance

- determine the concentration of a solution

- identify an unknown chemical

redox - a reaction in which reduction and oxidation occurs > oxidation is loss of e- (increase of oxidation no.) and reduction is gain of e-'s (decrease of oxidation no.)

rules:

- any uncombined element = 0

- monatomic ion = to the charge on the ion

- more electronegative element in a binary compound = the number equal to the charge it would have if it were an ion

- fluorine compound = -1

- oxygen = -2, unless it is combined with F (when its +2) or it is a peroxide (e.g. H2O2 or Na2O2) then it = -1

- hydrogen = +1, unless it is combined with a metal then its = -1

- in compounds, elements from group 1 and 2 and aluminium = +1, +2, +3

- the sum of oxidation numbers of all atoms in neutrals compound = 0

- the sum odd the oxidation numbers of all atoms in a polyatomic ion = the charge of the ion