Atoms and reactions Module 2 Flashcards
How do you work out amount of neutrons in an atom?
Mass number - amount of electrons
What’s an isotope?
Isotopes of an element are atoms with the same number of protons but different numbers of nuetrons
What’s the relative atomic mass?
The weighted mean mass of an atom of an element compared to 1/12th of the mass of a carbon atom of Carbon-12
What’s the relative isotopic mass?
The mass of an atom of an isotope compared with 1/12th of of the mass of an atom of C-12
Can can RFM be found out with isotopic abundances?
Multiply each relative isotopic mass by it’s by it’s %
Divide by 100
Can also be worked out using mass spectrometry, abundance on y axis, mass/charge on x
Use same technique (be aware abundance might not add up to 100, so divide by sum of all isotopic abundances)
What’s avagardos number (the number of particles in one mole)?
6.02x10^23
How do you work out number of moles when given amount of particles?
Moles = Number of particles you have / number of particles in one mole (6.02x10^23)
Formula for moles involving mass?
Moles = mass / RFM
Formula for moles involving gases?
Moles = volume in dm^3 / 24 dm^3
What’s the ideal gas equation?
pV = nRT
p = pressure in pascals V = volume in m^3 (1cm^3 = 1 x 10^-6 m^3, and 1dm^3 = 1 x 10^-3 m^3) n = number of moles T= temperature in Kelvin
What’s the empirical formula?
Smallest whole number ratio of atoms of each element in a compound
What’s the molecular formula?
Gives the actual number of atoms of each type of element in a compound
How do you work out the empirical formula and then the molecular formula?
You will be given the elements in compound and there masses or percentages
Divide each percent or mass by the elements RFM
Divide everything by smallest value to get everything into whole number ratio
Then to find molecular you will given the total RFM of compound and then see how much you have to multiply the empirical to reach the RFM this will give you the molecular formula
How do you write ionic equations?
Write the full equation down
Split everything that’s (aq) into into it’s ions
Cross out any ions that appear on both sides
Nitrate ion formula?
NO3-
Carbonate ion formula?
CO3(2-)
Sulphate ion formula?
SO4(2-)
Hydroxide ion formula?
OH-
Ammonium ion formula?
NH4+
Zinc ion formula?
Zn 2+
Silver ion formula?
Ag +
What’s a hydrated salt and what’s an anhydrous salt?
Hydrated salt contains water of crystallisation
Anhydrous salt doesn’t contain water of crystallisation
How do you work out moles of water in a water of crystallisation question?
Find number of moles lost by doing:
Find mass of water by doing mass of Hydrated salt - mass of anhydrous salt, and dividing that value by RFM of water
Find moles of ANHYDROUS salt, using moles = mass/rfm
Find how ratio when there is one mole of anhydrous salt how many there will be of water
What’s an acid?
Produce H+ ions in (aq) solution
Proton donor
What’s an alkali?
Bases that Release OH- ions in (aq) solution
What’s a base?
A proton acceptor
What’s a strong acid?
Fully dissociates in water
What’s a weak acid?
Partially dissociates in water
What do you get if an acid reacts with a salt and what’s the reaction called?
Neutralisation reaction
Salt + water produced
Metal + acid =
Metal salt + hydrogen
Metal oxide + acid =
Salt + water
Metal hydroxide + acid =
Salt + water
Metal Carbonate + acid =
Metal salt + CO2 + water
Ammonia + Acid =
Ammonium salt
How do you work out number of moles when given concentration?
Moles = concentration (mol dm^-3) x volume (dm^3)
How to titration calculations?
Write the balanced equation and solve as normal using information given
What’s the theoretical yield?
Mass of product you would get if no chemicals are “lost”
What’s the percentage yield?
(Actual yield (experimental) / theoretical yield)) x 100
Why is it important to develop methods which are sustainable?
High atom economy needed, as otherwise lots of waste produced , which need to be separated and harm the environment
Reactant chemicals are expensive so don’t want to waste them
Want reaction conditions which don’t require high temperatures or pressures as expensive and bad for environment
Use renewable resources
All oxidation number rules?
Uncombined elements have oxidation number of 0, eg Cl2 or Ag
For an ion the oxidation number is the same as the charge
For molecular ions the sum of the oxidation number is the same as the charge of the molecular ion
For a neutral compound the sum of the oxidation numbers is 0
Oxygen always has oxidation number -2, except in peroxides when it’s -1 and in O2 it’s 0
Hydrogen always has oxidation number +1, unless in metals when it’s -1 and in H2 it’s 0
Roman numerals tell you the oxidation number aswell
What’s oxidation?
Loss of electrons, increase in oxidation number
What’s reduction?
Gain of electrons, decrease in oxidation number
What’s an oxidising agent?
The thing which has been reduced
What’s a reducing agent?
The thing which has been oxidised
What’s a redox reaction?
When oxidation and reduction occur in the same reaction
What was the plum pudding model?
Solid positively charged sphere with negative electrons embedded in it
How did rutherford show that the plum pudding model was wrong, and what 3 facts did this prove?
Fired alpha particles and a thin sheet of gold
From plum pudding model expected most of the alpha particles to be deflected very slightly
In fact most of the alpha particles passed straight through or reflected backwards
This proved that:
There is a tiny positively charged nucleus at the centre of the atom, where most of the mass in concentrated
The nucleus is surrounded by a cloud of negative electrons
Most of the atom is empty space
What does the final bohr model of the atom state?
Electrons can only exist in fixed orbitals, or shells and not anywhere inbetween
Each shell has a fixed energy
When a electron moves between shells electromagentic radiation is emitted or absorbed, and will always have a fixed frequency
Why did the bohr model prove the rutherford model wrong?
A cloud of electrons around the nucleus of an atom would spiral down into the nucleus causing it to collapse
How did the bohr model explain the lack of reactivity in noble gasses?
The shells of atoms can only hold fixed numbers of electrons, and atoms will react to get a full shell, and noble gasses already have a full shell
When working out the amount of ATOMS in a molecule what do you need to be careful of?
Once you worked out the amount of molecules (same as particles using the formula), need to multiply it by the amount of atoms in the molecule
What colour does methyl orange go from when goes acidic to alkali?
Red to yellow
What colour does phenolphalein go when goes from acidic to alkali?
Colourless to pink
Formula for atom economy?
Molecular mass of desired products / sum of molecular mass of all products
Definition of an addition reaction?
The reactants combine to form a single product, so has 100% atom economy
Definition of a substitution reaction?
Where atoms from one reactant are swapped with atoms from another reactant, always results in at least 2 products
