Titration Curve:(M(n+) with EDTA ⇒Y(4-) )
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M(n+)+Y(4-) ↔ MY(n-4)
Ca(2+) → n=2 → Ca(2+)+Y(4-) = CaY(2-4)=CaY(2-)
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[email protected], 05/10/2016
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Definition : me=[M(n+)] = (Fraction remaining * initial concentration *dilutionfactor)=f1*f2*f3
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volume , concentration
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give : M(n+) → [M(n+)] , yy ml , U Molair conc (erlenmeyer flask)
added
EDTA → [y(4-] , xx ml , W Molair conc (buret)
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kf = formation constant = [MY(n-4)]/([M(n+)]*[y(4-)])
edta = polyprotic acid (= tetraprotic weak acid)
[Y(4-)] = alpha(4) * [EDTA] ,alpha(4) = f(h,ka1,ka2,ka3,ka4)=g(pH,ka1,ka2,ka3,ka4)
rem : kfc ,conditional formation for complexes.
kfc = kf * alpha(4) = [MY(n-4)]/([M(n+)]*[EDTA])=(my)/(me*edta) = kf *alpha4
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Before EP:
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xx=0 ml,w no EDTA ,yy ml concentration U
find general equation ,yy,u,w ( rule : v*t = v'*t', v' = (v*t)/t',from analytical chemistry, v'=z )
(%i1) | kill(all)$ |
(%i1) | p1 : z = (yy*u)/w; |
(%i5) |
p2:f1=(z-xx)/z; p3:f2= u; p4:f3= yy/(yy+xx); p5:f = rhs(p2)*rhs(p3)*rhs(p4); |
(%i6) | p6:me=ev(rhs(p5),p1); |
(%i7) | p7:ev(rhs(p6),xx=0); |
xx < > 0,ml,w EDTA,yy concentration U, ( use: z-xx >0),FreeM_before = me
(%i8) | p8:p6; |
By EP:
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xx=z ml,w EDTA,yy ml concentration U
(%i9) | p9:me=ev(rhs(p5),xx=z); |
me = 0 ? all MY_VAL
M(n+)+EDTA ↔ MY
0 0 my_val ?
(%i11) |
p10:my_val=u*yy/(yy+z); p11: kfc=kf*alpha4; |
find free [M(n+)] :freeM =[M(n+)]
M(n+) + EDTA ↔ MY
conc initial 0 0 my_val
conc formation freeM freeM my_val - freeM
(%i15) |
p12: my_ep = my_val - freeM; p13: me_ep = freeM; p14: edta_ep = freeM; p15: kfc = my_ep/(me_ep*edta_ep); |
(%i16) | p16:my_ep=ev(rhs(p12),p10); |
(%i17) | p17:kfc=ev(rhs(p15),p16); |
(%i18) | p18:kfc=ev(rhs(p17),p13,p14); |
(%i19) | p19:solve(p18,freeM); |
only positive solution ?
(%i21) | p20:part(p19,2); |
after EP:
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xx > Z ml:w EDTA ⇒ z < x_excess=xxx, freeM_after = [M(n+)]
(%i26) |
p21:edta_after=w*(xxx/(yy+z+xxx)); p22:my_after =u*(yy/(yy+z+xxx)); p23:kfc = my_after/(freeM_after*edta_after); |
(%i27) | p24:kfc=ev(rhs(p23),p21,p22); |
(%i29) | p25:part(solve(p24,freeM_after),1); |