Chemistry past paper corrections 2017 Flashcards
What is and isn’t an isotope?
Where it has the same number of protons but a different number of neutrons
An isotope can be the same as the normal amount given on periodic table
How do aqueous transition metals react with bases?
They donate an H+ off of their H2O ligand to the OH- ion from the base to leave OH- ligand attached to the transition metal
What is a rule about mole fractions?
They always add up to 1
They are basically a percentage of the whole mole
What is the shape of a molecule with 4 bonds?
Tetrahedral
What is the shape of a molecule with two bonds and two lone pairs?
Non-linear
Why do boiling points of simple covalent molecules increase down the group?
Because they’ve got more electrons
So they have more/stronger London forces
Why does reactivity down group 2 increase?
Because there is more electron shielding
Electrons are less attracted to the nucleus
Ionisation energy decreases
Less energy is needed to remove an electron
What does systematic name mean and what does it need?
Name of a molecule and it needs the oxidation number of the molecule
eg potassium dichlorate needs (VII) which is the oxidation number of chlorine in KClO4
What is an easy mistake that you can make when writing any equation to do with enthalpy?
It is always going to 1 mole of the product, so dont write
Br2 —-> 2Br, write 1/2 Br2 —> Br
What must you write when explaining the entropy change?
That —– has more/less disorder
eg. there is a solid in the products which has less disorder
What is the charge on NO3?
-1
What is the link between a graph and Gibbs free energy?
The equation for Gibbs free energy can be linked to y=mx+c
How must you write Kp?
With round brackets, NOT SQUARE
p —–
What does it mean when it says indicate the scale of working?
Write the actual volume of the apparatus eg. 1000 cm3 or 1 dm3
How can the rate of reaction be measured?
By measuring the loss of mass
By measuring the amount of gas given off
What are the units for the rate constant from ln2/half life?
s-1
When talking about equilibrium, what must be specified?
The direction of the reaction
eg. the FORWARD reaction is endothermic
Why is low pressure or low temperature not used as conditions?
Because there is a slow rate of reaction
Why is high temperature not used as conditions?
Because it uses a large amount of fuel
Even if you think you got the question wrong, what do you need to check?
Significant figures and units
When working out conjugate acid base pairs, what do you need to do?
Work out which one is more likely to lose a hydrogen
- Look at Ka values, higher one is stronger acid
- Look to see if there is an electronegative group on it which will make it more stable when dissociated
If volume of a buffer solution increases, what will happen to the Ka value?
Stay the same because proportion of HA/A- is the same
What needs to be watched out for when taking about oxidation and reduction in standard electrode potentials?
Reducing agent = oxidised
Oxidising agent = reduced !!!
What is the formula of the blue precipitate formed when NH3 is added to [Cu (H2O)6 ]2+ solution?
Cu(OH)2
Because H2O loses an H+ to become OH- ligands
This is not ligand substitution yet
