| Abstract | Staklo je jedan od najvažnijih materijala u svakodnevnom životu, u kojem se pojavljuje posvuda, a razlog zbog kojeg se tako često koristi je njegova kemijska stabilnost. Kemijski je stabilno zbog svoje amorfne strukture odnosno izostanka pravilnog rasporeda atoma. Iako je staklo otporno na mnoge kemikalije, ono nije univerzalno inertno. Zadatak ovog diplomskog rada je bio u određenom vremenskog periodu, u nekoliko staklenih boca pohraniti različite koncentracije standardne otopine natrijevog fluorida, utvrditi utječe li pohrana tih otopina u staklu na promjenu koncentracije fluorida, odnosno događa li se interakcija otopine (fluorida) sa staklom. U eksperimentu su pripravljene otopine natrijevog fluorida u rasponu koncentracija 1,0×10 --6 do 1,0×10 -2 mol L -1 . Radnim otopinama u svakom mjerenju izmjeren je potencijal, konstruiran je graf ovisnosti potencijala o pF-vrijednosti koncentracija i metodom dodatka standarda matematičkim modelom određena koncentracija. Na temelju eksperimentalnih podataka doneseni su određeni zaključci. Najmanje odstupanje od očekivane koncentracije ispitivanih otopina zabilježeno je u otopini koncentracije 1,0×10 -2 mol L -1 , dok je najveće odstupanje zabilježeno u otopini koncentracije 1,0×10 -3 mol L -1 . Koncentracija otopine 1×10 -5 mol L - 1 je bila nešto malo viša u odnosu na očekivanu vrijednost kroz sva mjerenja. U nastavku eksperimenta uočeno je kako se prvotno izmjerene koncentracije previše ne mijenjaju, pri tome blago rastu ili padaju ali variraju oko početno izmjerenih vrijednosti. Iz grafičkog prikaza ovisnosti pF vrijednosti o danima mjerenja, kao i iz ovisnosti nagiba o danima mjerenja zaključeno je kako se koncentracije, iako u pojedinačnim mjerenjima blago rastu ili padaju, u konačnici ipak ne mijenjaju drastično što ukazuju i navedeni grafički prikazi iz kojih se vidi da su rezultati smješteni uglavnom linearno. Obzirom na to da se ni pri jednoj koncentraciji ne uočava kontinuirani pad vrijednosti kroz cijeli period mjerenja, zaključuje se da u ovom eksperimentu staklo ne utječe na koncentraciju fluorida. |
| Abstract (english) | Glass is one of the most important materials in everyday life, in which it appears everywhere, and the reason it is used so often is its chemical stability. It is chemically stable due to its amorphous structure, i.e. the absence of a regular arrangement of atoms. Although glass is resistant to many chemicals, it is not universally inert. The task of this thesis was to store different concentrations of a standard solution of sodium fluoride in several glass bottles for a certain period of time, to determine whether the storage of these solutions in glass affects the change in fluoride concentration, or whether the solution (fluoride) interacts with the glass. In the experiment, sodium fluoride solutions were prepared in the concentration range of 1,0×10 -6 to 1,0×10 -2 mol L -1 . The potential was measured with the working solutions in each measurement, a graph of the dependence of the potential on the pF-value of the concentrations was constructed, and the concentration was determined using the standard addition method using a mathematical model. Based on the experimental data, certain conclusions were drawn. The smallest deviation from the expected concentration of the tested solutions was recorded in a solution with a concentration of 1,0×10 -2 mol L -1 , while the largest deviation was recorded in a solution with a concentration of 1,0×10 -3 mol L -1 . The concentration of the solution 1,0×10 -5 mol L -1 was slightly higher compared to the expected value throughout all measurements. In the continuation of the experiment, it was observed that the initially measured concentrations do not change too much, while they rise or fall slightly, but vary around the initially measured values. From the graphical presentation of the dependence of the pF value on the days of measurement, as well as from the dependence of the slope on the days of measurement, it was concluded that the concentrations, although they slightly increase or decrease in individual measurements, ultimately do not change drastically, as indicated by the above graphical representations, which show that the results are arranged mostly linearly. Given that no continuous decrease in values is observed at any concentration throughout the entire measurement period, it is concluded that in this experiment the glass does not affect the fluoride concentration. |
