Chapter 4 Flashcards
What is a strong acid?
Completely dissociates in aqueous solution and released all its hydrogen atoms into solution as H+ ions.
What is a weak acid?
Only releases a small proportion of its H+ ions and partially dissociates in aqueous solution.
Example of strong acid?
HCL
Example of weak acid?
ethanoic acid (CH3COOH)
What is a base?
A base neutralises an acid to form a salt.
What is an alkali?
A base that dissolves in water and releases hydroxide ions into the solution.
Example of a base?
NH3
most metal oxides/hydroxides/ metal carbonates too
Example of an alkali?
NaOH
What is produced when an acid is neutralised by a metal oxide/hydroxide?
Salt and water only
eg. CuO + H2SO4 —> CuSO4 + H2O
What is produced when an acid is neutralised by an alkali?
acid + alkali = salt + water
H+ + OH- –> H2O
What is produced when an acid is neutralised by a metal carbonate?
metal oxide + carbonate = salt + water + CO2
ZnCO3 + H2SO4 —> ZnSO4 + H2O + CO2
What is a titration?
A technique used to accurately measure the volume of one solution that reacts exactly with another solution.
How do you prepare a standard solution?
1) solid is weighed
2) solid is dissolved in distilled water in a beaker
3) solution is transferred into a volumetric flask and the washings are rinsed into the flask with distilled water.
4) The flask is carefully filled to the graduation line by adding distilled water with a pipette.
5) The bottom of the meniscus has to be touching the mark.
6) The flask is inverted slowly several times.
How do you read a value from a burette?
Read the value from the top at the bottom of the meniscus.
What is an oxidation number?
The number of electrons involved in bonding to a different element.
What is the oxidation number of elements?
always 0
eg. H2/ O2/ Na/ Fe
What do the oxidation numbers in a compound add up to?
0
Is the sign after or before the oxidation number?
The sign is before.
How do we know the value of an elements oxidation number? What are the special cases?
The values are normally an elements charge but there are a few special cases;
1) H in metal hydrides = -1 (CaH2)
2) O in peroxides = -1 (H2O2)
3) O bonded to F = +2 (F2O)
What is OIL RIG
Oxidation
Is
Loss of electrons
Reduction
Is
Gain of electrons
What happens if an element is oxidised ?
It loses electrons and its oxidation number becomes higher.
What happens if an element is reduced ?
It gains electrons and its oxidation number becomes lower.
What is a redox reaction?
A reaction that involves reduction and oxidation.
What is a reducing agent?
An atom that becomes oxidised itself but causes another atom to gain electrons
