Chemistry 2 Flashcards
Elements are composed of atoms which may be linked to form
molecules
relative atomic mass Ar
the mass of 1 atom relative to 1/12 the mass of 1 atom of carbon-12
carbon-12 is the most common isotope of carbon and its mass is 12
Relative MOLECULAR mass Mr definition
-the mass of 1 molecule of an element or compound compared with 1/12th the mass of 1 atom of carbon-12
Relative MOLECULAR mass Mr HOW TO CALCULATE
addition of Ar atoms in molecule
the mole
A mole of carbon 12 Is the amount of chemical which contains exactly 12g of 12C
The Avogadro constant and what it is
12 /1.9926 x 10^-23 =6.022 x 10^23
1.9 is the mass of one atom
number of moles =
mass of 1 substance/mass of 1 mole (g)
molarity of solutions
the amount of solute in moles in 1 dm^3 of solution
calculating molarity of solutions
-convert to dm^3 for example if 10cm of 0.1 then 10/1000 x 0.1 is how many in dm^3
-then multiply by Mr
A large Kc value indicates
the product concentration is high and the forward reaction is favoured.
le chetiliers
poster
haber process
iron can be used as catalyst
weak acids and bases only
partially dissolve in water
The pH of a weak acid depends on two factors
-the concentration of the acid
-its pKa value (pKa = -log10 Ka)
to calculate the pH of weak acids …
-use the Ka formula to find concentration of [H]
-then put in log formula
strong bases
-fully ionised
-concentration of hydroxide (OH-) is equal to the concentration of the base
weak bases
-only partially ionised
-equlibrium is established
aqueous ammonia is the most common
weak base
the base ionisation constant
Kb = [BH+]
look at slide 14 on Acids and bases part 2
Henderson-hasselbalch equation
-possible to calculate the pH of a buffer solution
pH = pKa + log10 ([base]/[acid])
acid =
a substance which contains hydrogen and releases hydrogen ions (H+) when dissolved in water
base =
substance which reacts with an acid to form a salt plus water
acid is proton
donor
base is proton
acceptor
acid + base =
salt + water
how the atom arose
look on ppt atomic structure
atomic number
equal to the number of positive charges or protons in the atom
bottom left
labelled numbers
-atomic mass top = protons + neutrons
atomic number = protons + electrons unless isotope
if the atomic mass is different
number of neutrons changes
the 1st ionisation energy
defined as the energy required to turn 1 mole of an element in the gas state into 1 mole of its ions
patterns in ionisation energy increasing in reactivity across the periodic table
as you go up the table increase in charge and attraction
isotopes are elements containing atoms with the same
atomic number
but different atomic mass
they can be radioactive
intra molecular bonds
ionic
covalent
inter-molecular bonds
dispersion
a vertical column called a group contains elements with
similar chemical properties due to same number of valence electrons
horizontal row is called a
period
atomic number increases from left to right along the row
groups
-have same number of outer shell electrons
-down a group = increasing number of electron shells
-melting and boiling points decreases in groups 1 to 4 and increase In groups 5 to 8
atoms become larger
-group 1 and 2 elements become more reactive
-groups 6 and 7 elements become less
within periods they have the same number of electron
shells
across a period
-elements become more electronegative
-atomic radius decreases
-melting and boiling points rise to a peak (group 4) then fall
electronegativity increases across the periodic table
across and up
after passing an electron from the metal to non both adopt a
noble gas configuration
ionic bonding requires electron
transfer
another example of ionic bonds
ionic bonds can be pH sensitive and not all ionic bonds can be removed by electrolysis