76
V@-/
I = 2,47 mA#'NJ#&h&Y&8-/
x"f&I 0G>'?k
y"f&l''$σ2
Y&
"8&;7'I 0c’QN>&Y&
"l''$?V’*<X@V[&.&
!".&8-6JAE46@)HCOONa(s) → HCOO-
(aq) + Na+
(aq)
,"8&;7'@cY&)c = n
V = m
(M × V)
ABC)c = 0,010 mol.L-1
:"8&;7'Y&8-/<'&AX8@N)
=N'6@YXL#)
45)[Na+
(aq)] = [HCOO-
(aq)] = cABC)[Na+
(aq)] = [HCOO-
(aq)] = 0,010 mol.L-1 = 10
mol.m-3
F"f&@σ1
Y&)σ1 = λ(Na+
(aq)) × [Na+
(aq)] + λ(HCOO-
(aq)) × [HCOO-
(aq)]
&)[Na+
(aq)] = [HCOO-
(aq)] = c-)σ1 = (λ(Na+
(aq)) + λ(HCOO-
(aq))) × c
ABC)σ1 = (5,46.10-3 + 5,01.10-3) × 10 = 1,05.10-1 S.m-1
x"f&i 0G)G = I
U = 2,47.10-3
1,00 = 2,47.10-3 S
>'k)k = L
S = 1,00.10-2
3,21.10-4 = 31,2 m-1
y"f&σ2
Y&)σ2 = k × G = 2,47.10-3 × 31,2 = 7,69.10-2 S.m-1
";7'8&c’QN>&Y&)
Ya UX[F;7'R[-hfc;7'c’45)σ2 = (λ(Na+
(aq)) + λ(HCOO-
(aq))) × c’
-8')c’ = σ2/(λ(Na+
(aq)) + λ(HCOO-
(aq)))
A"C)c’ = 7,69.10-2/(5,46.10-3 + 5,01.10-3) = 7,35 mol.m-3
"?V’V[&.&)-8'iK&? /6&7h'QN>'&YXL)n = c’ × (V+ V’)
45)V’ = n/c’ – VABC)V’ = 1,0.10-3/7,35.10-3 - 1,0.10-1 = 3,6.10-2 L = 36 mL
8-fL&h100 mLY#S1
6J(b;7C1
#&h&.;f(_
89#6'(#Y&G1 = 1,22 mS
8-f&L`N&h?100 mLY#S2
b;76J(C2
.;f(_
89#6'(#Y&#&h&G2 = 1,44 mS
!"#i 0;7'74C1
;7'#hf37C2 ,"QG100 mL5V[&.d mLY#S1
Y&8-[ f&L&h?
;7'9H=J&CH=J&Y&C1
f&&Ul''$G3
Y&K]
:"T;&100 mLY#S1
100 mLY#S2
b;7-(H=J&Y&#C
#;7'V$'&U=E&C1
C2
f&&UI 0?G4
Y&
!"f&&G-Y&;7g6qI$');7'C1
Y&S1
'#hf;7C2
Y&
S2