past paper 2020 necessary flash cards
1
Q
why are organic compounds unable to dissolve in water?
A
they are unable to form hydrogen bonds
2
Q
why are ionic compounds soluble in water?
A
- the ionic compounds are hydrated
- the enthalpy of hydration compensates for the energy required to break the ionic lattice
3
Q
why are ionic compounds unable to dissolve in organic compounds?
A
- they can only form weak london forces which are smaller in magnitude than the energy required to break the ionic lattice
4
Q
why wont strong acids form buffers?
A
because they dissociate fully in solution
5
Q
what is the difference between transition metals and d block elements?
A
- d block: last added election in the d subshell
- transition metal: form a stable ion with a partially filled d subshell
6
Q
how to find enthalpy using bond enthalpy?
A
reactants - products
7
Q
what is the equasion for gibbs free energy?
A
G= H - TS
8
Q
what is entropy of the surroundings?
A
H / T (times -1)
9
Q
why is 2 x the bond enthalpy for a single bond not the same as the bond enthalpy for a double bond?
A
- a double bond containes a sigma and a pie bond not 2 sigma bonds
10
Q
why does pressure not affect Kp?
A
- the equillibrium of the reaction shifts to counteract the change in pressure meanin Kp stays constant
- the ratio stays constant therefore there is no change
11
Q
what is the colour change from MnO4- to Mn2+?
A
colorless to pail pink
