2.1 atoms and reactions Flashcards
what’s an isotope?
atoms of the same element with a different number of neutrons and different masses
eg carbon-12 and carbon-14
what’s the charge of a proton, electron and neutron?
+1
-1
0
respectively
define relative isotopic mass
the mass of an isotope compared to 1/12th the mass of carbon-12
define relative atomic mass
the weighted* average mass of an atom compared to 1/12th the mass of carbon-12
*weighted - takes into consideration the abundance of each isotope
formula for relative atomic mass?
Ar = (isotope mass x %*) + (isotope mass x %) / 100
*% abundance of each isotope
describe how you form an ionic equation
split each ionic compound into its ions, except the solids!
cross out ions that appear on both sides of the equations
write out the remaining ions and compounds
what’s the value of avogadros constant?
Na = 6.02 x10^23
how do you calculate the number of particles? (incl. no. of atoms and ions)
no. of particles = moles x Na
how many particles in 1 mole of Fe?
moles x Na
1 x 6.02 x10^23
= 6.02 x10^23 particles
what might you use mass spectrometry to determine? name 2 things
the relative isotopic masses and relative abundances of the isotope
calculating the relative atomic mass of an element from the abundances of its isotopes
what’s molar gas volume?
gas volume per mole (unit: dm^3 mol^–1)
what’s empirical formula?
simplest whole number ratio of atoms of each element in a compound
how do calculate the empirical formula?
divide the mass or percentage by the Mr to find the moles (for each element)
divide all molar values by the lowest value of moles from the atoms in the element
multiply up to get ‘whole numbers’
eg 1.33 x 3 or 1.25 x 4 or 2.5 x 2
multiply each value by the same number
define molecular formula
the amount of atoms in each element in a molecule eg C2H4 - (not simplified to the lowest ratio)
what does structural formula show?
it shows how the compound would be drawn out
eg C3H5COOH - the different elements aren’t collected together but they are spread out to show how it would be drawn structurally
what’s a hydrated salt?
a salt with water trapped in the ionic lattice
what is ‘water of crystallisation’?
the water trapped in a salt during the crystallisation process
how do you dehydrate a salt?
evaporate water
what do you call a salt that has has the water evaporated out of it?
an anhydrous salt
give the equation involving moles, mass and Mr
mass = moles x Mr
if you’re given the volume of a gas, how would you find the moles? (equation)
moles = volume / 24
or for cm^3
moles = v / 24000
name the equation involving moles conc and vol
moles = concentration x volume
name the ideal gas equation
pV = nRT
what’s the gas constant?
8.314
what’s the pressure and temp at RTP?
101325 Pa or 1 atm
298 K or 25 degrees C
how do you convert from cm^3 to dm^3?
divide by 1000
how do you convert from dm^3 to m^3?
divide by 1000
how do you convert from degrees C to kelvin?
add 273 to degrees C
define percentage yield
the amount (mass or moles) of product obtained compared to the theoretical yield of product
how do you calculate percentage yield?
actual yield/theoretical x 100
define atom economy
how much of the reactants were wasted / how much of the products were useful
how to we calculate atom economy?
Mr of desired products/Mr of all product x 100
what do we have to take into account when calculating the Mr of something to find atom economy?
the large number infront of atoms or molecules. e.g. the Mr of 2H₂ = 4 NOT 2
define acid
a substance that releases H+ ions in an aqueous solution
whats the formula for: hydrochloric acid? sulphuric acid? nitric acid? ethanoic acid?
hydrochloric acid: HCl
sulphuric acid: H₂SO₄
nitric acid: HNO₃
ethanoic acid: CH₃COOH
whats the difference between strong and weak acids?
strong acids completely disassociate and release all H+ ions.
eg HCl –> H+ + Cl-
but, weak acids only partially disassociate and only release some H+ ions
e.g. CH₃COOH –> CH₃COO- + H+
what is a base?
a substance that accepts H+ ions
will neutralise an acid
does not dissolve in water
whats an alkali?
a substance that releases OH- ions in an aqueous solution
whats the formula for:
sodium hydroxide?
potassium hydroxide?
ammonia?
sodium hydroxide: NaOH
potassium hydroxide: KOH
ammonia: NH₃
acid + metal carbonate ?
acid + metal carbonate ➝ metal salt + water + carbon dioxide
metal + acid ?
metal + acid ➝ metal salt + hydrogen
metal oxide + acid ?
metal oxide + acid ➝ salt + water
metal hydroxide + acid ?
metal hydroxide + acid ➝ salt + water
define anhydrous
a term used to describe a substance with no water
what does hydrated mean in relation to salts?
a hydrated salt means there are water molecules trapped in the giant ionic lattice of the salt
what is an oxidation number/oxidation state?
the number electrons an atom uses to bond with atoms of other elements.
whats the oxidation number of an uncombined element? e.g. C, O₂ or Na
0
whats the oxidation number of oxygen (mostly all the time)?
-2
whats the oxidation number of oxygen in peroxides (O₂-2)?
-1
whats the oxidation number of hydrogen (mostly always)?
+1
whats the oxidation number of hydrogen in a metal hydride?
-1
whats the oxidation number of a monatomic ion?
the charge of the ion. e.g. Na+1 would have an oxidation number of +1
what does the charge of a molecular ion tell you about the oxidation number?
the charge tells you the overall oxidation number. the oxidation numbers of the atoms in the molecular ion will add to this number.
eg SO₂-2 - the oxidation no. of the molecular ion = -2 so the oxidation no.s of S and O₂ will add to -2
what does a roman numeral tell you about an atom?
tells you the magnitude(value) of the oxidation number. eg Fe(II) would have an oxidation number of +2
what is the oxidation number of sulphur in a sulfate(IV) ion?
+4
what is the oxidation number of nitrogen in a nitrate(III) ion?
+3
what is oxidation in terms of electron transfer?
oxidation is the loss of electrons OIL
what is reduction in terms of electron transfer?
reduction is the gain of electrons RIG
what is oxidation in terms of oxidation number?
oxidation is an increase in oxidation number
what is reduction in terms of oxidation number?
reduction is the decrease in oxidation number
in reactions, are metals usually oxidised or reduced? why?
metals are oxidised because they lose electrons to become positive ions
in reactions, are non-metals usually oxidised or reduced? why?
non-metals are reduced because they gain electrons to become negative ions
what is an oxidising agent?
something that accepts electrons
it oxidises something
and reduces it self because it gains electrons
what a reducing agent?
something that donates electrons
it reduces something
and oxidises itself because it loses electrons
