Vpliv kovinskih ionov na zvrsti citronske kisline v odvisnosti od pH

Hodžič, Sara (author), Kozlevčar, Bojan (mentor)

Pripravila sem raztopino citronske kisline (H4L) v vodi, ter vsakemu delu le- te dodala po eno izbrano zvrst kovinskih kloridov (NaCl, CaCl2, ZnCl2 ali CuCl2). Vsaki od teh raztopin sem nato dodajala raztopino NaOH do nevtralizacije raztopine. Vsem raztopinam je pH sorazmerno enakomerno naraščal do pH = 7. Bistvena razlika je bila pri Cu2+, kjer se je za nevtralizacijo porabila dvojna količina NaOH. Očitne razlike sem opazila pri merjenju prevodnosti, kjer je ob dodajanju močnega elektrolita NaOH prevodnost enakomerno naraščala le pri enovalentnih natrijevih ionih, pri ostalih (torej dvovalentnih) pa so vidna tudi izrazita upadanja prevodnosti. Takšne krivulje se skladajo s predvideno boljšo možnostjo vezave dvovalentnih kovinskih kationov na anion citronske kisline. Te pojave sem primerjala s tremi znanimi bakrovimi spojinami v tem sistemu [Cu2(L)(H2O)2]n, (CN3H6)4[Cu2(L)2](H2O)2 in (CN3H6)[Cu2(OH)(L) (CN3H5)2], katere sem sintetizirala po opisih v virih. Istovetnost teh trdnih spojin sem potrdila z elementno in praškovno rentgensko analizo, ter z IR ponovljivost sintez.

• Language: Slovenian
• Keywords: citronska kislina, kovinski ioni, pH, elementna analiza, rentgenska praškovna analiza, IR spektroskopija
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2019
• PID: 20.500.12556/RUL-110564
• COBISS.SI-ID: 1538435779
• Publication date in RUL: 17.09.2019

Secondary language

• Language: English
• Title: Metal ions influence on different citric acid species in relation to pH

Abstract

A solution of citric acid (H4L) was prepared in water, to a portion of which one selected type of metal chlorides (NaCl, CaCl2, ZnCl2 or CuCl2) was added. To each of these solutions the NaOH solution was added until neutralized. The pH of all solutions rises steadily till pH =7, , with the most obvious difference for Cu2+, for which double amount of NaOH was needed for the neutralization. The most obvious differences were noticed at conductivity measurements, where with a strong electrolyte, namely NaOH was adding, the conductivity steadily rises only for the monovalent sodium ions. On other hand, with the other metal ions (notably divalent) clearly conductivity decreases are seen. These curves are consistent with the anticipated better ability of the divalent metal cations binding to the citric acid anion. These observations were compared to three of the known copper compounds in this system, namely [Cu2(L)(H2O)2]n, (CN3H6)4[Cu2(L)2](H2O)2 and (CN3H6)[Cu2(OH)(L)(CN3H5)2], being synthesized as previously described in resources. The identity of these compounds was confirmed by elemental and powder X-ray analysis, while the IR was applied for the synthesis reproducibility checking.

• Keywords: citric acid, metal ions, pH, elemental analysis, X-ray powder analysis, IR spectroscopy