Chapter 4 Acids and redox Flashcards
Acid
A species that releases H+ ions in aqueous solution.
Strong acid
An acid that dissociates completely in solution.
Weak acid
An acid that dissociates only partially in solution.
Base
A compound that neutralises an acid to form a salt
Neutralisation
A chemical reaction in which an acid and a base react together to produce a salt.
Salt
The product of a reaction in which the H− ions from the acid are replaced by metal or ammonium ions.
Alkali
A type of base that dissolves in water forming hydroxide ions, OH–(aq) ions.
Common acids
Hydrochloric acid (HCl), Sulphuric acid (H2SO4), Nitric acid(HNO3), Ethanoic acid (CH3COOH)
Common bases
Metal oxides- MgO CaO CuO
Metal carbonates- Na2CO3 CaCO3 CuCO3
Alkalis- NaOH KOH NH3
Neutralisation of an acid by a metal oxide/hydroxide
acid + metal oxide/hydroxide -> salt + water
acid + alkali -> salt + water
Neutralisation of an acid by a metal carbonate
acid + metal carbonate -> salt + water + carbon dioxide
Titration
A technique use to accurately measure the volume of one solution that reacts exactly with another solution
Titrations can be used for
- finding the concentration of a solution
- identification of unknown chemicals
- finding the purity of a substance
Standard solution
A solution of known concentration
Made with a volumetric flask
End point
The point in a titration where the indicator changes colour; the end point indicates when the reaction is just complete.
Titre
The volume added from the burette when the volume of one solution has exactly reacted with the other solution.
Concordant
Values agreeing within 0.10cm^3
Oxidation number
A measure of the number of electrons that an atom uses to bond with atoms of another element. Oxidation numbers are derived form a set of rules.
Rules for oxidation number
- always 0 for elements
- oxidation no. has a sign before the number
- O -2, H +1, F -1, Na K +1, Mg Ca +2, Cl Br I -1
H in metal hydrides -1
O in peroxides -1
O bonded to F +2
Sum of the oxidation numbers = total charge
Oxidation
Loss of electrons or an increase in oxidation number.
addition of oxygen
Reduction
Gain of electrons or a decrease in oxidation number.
Removal of oxygen
completely dissociates
releases all hydrogen atoms into solution as H+ ions
Partially dissociates
releases only a small proportion of hydrogen atoms into solution as H+ ions
