Chemistry pre-2017 paper corrections Flashcards
What are polyamides used for?
Making fabrics like nylon
What is the attraction in chromatography called?
Adsorbtion
What is the isoelectric point?
The pH that an amino acid exists as a zwitterion
What is the difference between producing an amino acid in a lab or using bacteria?
In the lab two optical isomers are formed/racemic mixture
Bacteria only form one product
In mass spectrometry, what must all the species be?
Positive in order to show up on the spectrum
What are the products of hydrolysis of the amide bond with HCl?
a carboxylic acid COOH and NH3+
How many [H] are there in reduction of aldehydes to alcohols?
2[H]
How can melting points of ionic compounds be determined?
By the size of their radius
This is due to their ELECTRON/CHARGE DENSITY so you have to add up the sum of the radii of the two ions
When talking about when Gibbs Free Energy is feasible, what is good to write?
When talking about when /\G is negative, talk about not just T/\S but when /\H - T/\S > 0
What do you need to remember when calculating Kc?
To use concentration, not moles
Why might a reaction be unlikely to take place in just one step?
Because the stoichiometry in the rate equation doesn’t match the overall equation
Because a collision is unlikely to occur with more than 2 ions
Why is scandium not a transition metal?
Its ion doesn’t have and incomplete d subshells
All its d orbitals are empty
Why is zinc not a transition metal?
Its ion doesn’t have and incomplete d subshells
All its d orbitals are full
When drawing transition metal ions what is easy to forget but often isn’t needed anyway?
The brackets and charge on the ion
How does ligand substitution allow haemoglobin to transport oxygen in the blood?
O2 bonds reversibly to the Fe2+ ion
O2 can be released
What do you need to mention when explaining why a buffer solution has formed?
The actual names of the acid and the salt eg. CH3CHOOH and CH3COO-
What is the definition of standard electrode potential?
The e.m.f of a half cell compared to the standard hydrogen electrode
What are the standard conditions of the standard electrode potential?
25 degrees, 1 moldm-3 and 1 atm
Why does the cell potential increase when water is added to a Cu2+/Cu half cell?
- Because the concentration of Cu2+ decreases because it reacts with the water
- This makes the equilibrium shift to the left to replace the lost ions
- This means more electrons are released by Cu
- So the cell has a bigger difference in E
What do you need to include when talking about which is the reducing agent?
That the reducing agent loses electrons because it is oxidised
Also which species it loses the electrons to
When there is a transition metal ion present and it forms a precipitate, what is likely to be the solid compound?
Ending in (OH) eg. Fe(OH)3
What is a molecular formula?
Just the simplest formula of number of atoms
eg. C2H6O
In precipitation reactions, how do you know how many ligands to add?
You add them until the oxidation number is 0
For most of them this will be 2 as they are 2+ ions
But it might be 3 if it is a 3+ ion
In ligand substitution, how do you know how many ligands to swap?
For some it will be a full substitution, but for some like copper and excess NH3, it is only partial substitution and will make [Cu(NH3)4(H2O)2]2+. This is redissolving
