7e Flashcards
how can we make a dispersion more stable
- put more energy into it to form smaller particles
- focus on the surfactant to get a stable microemulsion system ( polymer for steric stabilisation or make them charged )
if the CMC = 7.4mM ,, what is 🔺G
🔺G = RT ln(X cmc)
c meaning mole fraction so u want the mole fraction !!
first turn 7.4mM –> 7.4M
7.4mM = 7.4 x10^-3M
then find mole fraction.
7.4x10^-3 / (7.4x10^-3) + 1000/18
= -22121.79 jmol-1
= -22.1 kjmol-1
if theres a silver nanoparticle coated in amine functionalised polymer,, why is it more stable at lower than at higher PH
- polymer = steric stabilisation
- amine = NH2 = neutral
- low pH amine = NH3+ = charged
- these repel when they come closer,, meaning theyre more repulsive,, meaning the graph peak is higher = more stable bc molecules are less likely to aggregate.
when we are asked to sketch a graph of the attractive,, repulsiove and total interaction energies very with interparticle separation,, what should we think of
that one long lecture with the diff weird graphs
the one where the top bit is repulsive
the lower bit is attractive
interparticle sep is the x acis and interaction energy is the y axis.
how can interparticle forces in colloidal silica be controlled using NaCl salt and how does this alter the stability of the dispersion
silica is a charged colloidial dispersion
- adding more salt means the charges attract
- lowering the Ea of that one hill on the graph bc the forces arent repulsive,, meaning the dispersion is less stable bc theres a lower Ea meaning its easy to overcome bc 3/2KT > Ea.
