cgier 34 Flashcards
the dissolution and precipitation of limestone ( CaC03) is responsible for the formation of
limestone caverns in featuring statlactics and stalagmites
the solubility phenomena is important as: nail –> na + cl because its important for — like:
- biological process
- important for absorption of nutrients
- important for mineralisation
- application in drug silvery and diagnostic process
solubility equilibria is in — solutions where dynamic equilibrium exists between — and — and the rate of the —- is — to the rate of —- and the concentration of ions will be —
- staturated
- undissolved solids
- ions
- dissolutions equals the rate of precipitation
- constant
solids dissolving to form aqouse solutions as:
- ionic solid ( CaF2) — to form completely separate — and —
- as dissolution proceeds the ca2+ and f- will —-
- which will lead to – probability of ions colliding to —
- second competing process is going the opposite directions
- going right is: — and going left is —
- at equilibrium the solution is said to be —
- dissolves to from hydrated cations ca2+ and fe- anions
- increases , increases
-dissolution - precipitation
- saturated
— is the constant for the equilibrium between solid solutes and ions in saturated solutions
- solubility product constant ( ksp)
- ksp= dissolved ions only aka the product and no solids
why there’s no solids in ksp?
more solid leads to – in surface area which — the solubility which gives greater chance for ions to reform into —
- greater , greater
- solids
solubility product has only — value for a given solid at a particular temp
one value
solubility product has – number of values at a given temp depending on their condition( as ph, common ion ) that impacts the solubityy
- infinite
– is the number of moles of substance that can be dissolved in 1 litter for solution reaching saturation
molar solubility
the molar solubility can be calculated from — and — and the units are —-
- solubility product constant ( ksp ) and stoichometric coefficient
- mol/L
example: calculate the ksp for CaF2 if the molar solubility of CaF2 is 3.4 x 10-4 mol/l
formula: caf2 –> ca2+ + 2f-
ksp = dissolved ions
= [3.4 x 10-4 ] x [2 x 3.4 x 10-4]power 2
= [ 4 x 3.4 x 10-4 ] power 3
— are direct indicators for solubility for different salts if the salts produce the same number of ions
larger the KSP – the solubity
- ksp
- larger
ksp can’t be used as a direct comparison of solubility for salts that produce — number of ions in a solution
- different
solubility is – when in the presence of a second sole which is known as —- effect
- lowered
- common ion effect
ph affects the —
as we increase the ph —–
as we decrease the ph
- solubility
- decreases , increase of 0H , left
- increases , decrease of OH , right
the impact of ph in the following equation:
Ag3PO4 (s) —> <— 3Ag+ (aq) + PO43- (aq)
( PO4 3- is a weak base which will create H+ to from HPO4 -2)
increase of the ph decreases the solubility and decrease in PO3
here the solubility will increase bc of the po4that’ll drive the equilibrium to the right
application of solubility:
- drugs development by having low ksp
- dental health
barium sulphate is a – metal and is used for — adminstered as suspension. Its toxic but by —- it won’t get —
- heavy metal
- contrast agent for x rays
- having low solubility
- won’t get absorbed by the patient
tooth decay occurs due to bacteria producing — that – the ph.
the main component of the teeth is hydrocypetate and is more soluble at —
- acids , decreases the ph
- low ph
formula of tooth decay is — and the reverse is called —- cavities can develop when its slower than — of hydroxyapatite
-Ca5OH(PO4)3 (s) –> <– 5Ca2+ (aq) + 3(PO43-) (aq) + OH- (aq)
- reminerlasion
- slower than dissolution
fluoridation of water
For decades many countries have been adding CaF2 to drinking water.
CaF2 increases the concentration of F- in the saliva.
During remineralisation fluorapatite, Ca5F(PO4)3, can be formed in the enamel of teeth and at a faster rate than hydroxyapatite reforms.
Fluorapatite is less soluble at acidic pH values compared to hydroxyapatite and therefore reduces probability of developing tooth decay.
Ca5F(PO4)3 (s)–> <– 5Ca2+ (aq) + 3(PO43-) (aq) + F- (aq)
solubility of drugs can be significantly modified by forming — the solubility will — but certain counter ions — the solubility
- salts ( which impacts the choice of salts )
- increase , decrease
- information:
Erythromycin is unstable at low pH. Erythromycin stearate is less soluble and therefore less susceptible to degradation. The salt dissociates in the intestine and can be absorbed.
Formulations developed for oral administration need to take into account the high concentrations —
-cl- ions in the stomach
-Poorly soluble salts containing a Cl- counter ion may precipitate and therefore become less available for absorption due to the common ion effect of the Cl- ions
Doxycycline.HCl – common ion effect
4 times more soluble in pure water compared to 0.1 M HCl
More soluble in 0.1 M methylsulphonic acid compared to HCl
Specificity for Cl- ions, i.e. common ion effect
calculate:
Lead(II) iodide, PbI2, has a Ksp of 7.1 x 10-9 at 25 o C. Calculate the molar solubility of PbI2 in water at 25 o.
PbI2 –> ,<– Pb2+ + 2I-
Ksp = [Pb2+] [I-]2 = (s)(2s)2 = 7.1 x 10-9
4s3 = 7.1 x 10-9
s3 = 1.8 x 10-9
s = (1.8 x 10-9)1/3 = 1.2 x 10-3
