Wet Analytical Methods: - Volumetric - Gravimetric Pengukuran VOLUME larutan Volume larutan standar yang bereaksi dengan ANALIT yang ingin diketahui konsentrasinya Analisis VOLUMETRIK = TITRIMETRIK

Volumetric vs Titration Volumetric Analysis The quantitative determination of the concentration of one substance by titration against a substance of known concentration. Titration A solution of known concentration (the standard) is added via buret to a solution of unknown concentration until all of the unknown solution is consumed at the Endpoint (Equivalence Point or Neutralization Point). Indicator undergoes permanent color change.

Komponen analisis volumetrik Lar. Standar/baku (TITRANT)‏ Unknown analyte (TITRAT)‏ Reaksi Titrasi Indikasi Titik ekivalen Titik akhir

Syarat reaksi Jenis reaksi Reaksi hrs berlangsung cepat Reaksi berlangsung secara kuantitatif Tidak ada reaksi samping Reaksi hrs kuantitatif  kesetimbangan reaksi hrs jauh ke kanan. Jenis reaksi Asam-basa : asidi-alkalimetri Redoks : yodometri Kompleks : kompleksometri Pengendapan : argentometri

TITIK EKIVALEN vs TITIK AKHIR Ketika volume (jumlah mol) larutan standar yang ditambahkan tepat sama dengan yg diperlukan untuk bereaksi sempurna dg larutan analit disebut TITIK EKIVALEN Volume larutan standar yang teramati yang diperlukan dalam suatu titrasi disebut TITIK AKHIR

Titration Equivalence Point – This is the point in which the amount of titrant added is equal to the stoichiometric reaction with the analyte. Titration End Point – The end point is the detection of a physical characteristic which indicates that the equivalence point is reached. Generally voleq.pt. ≠ volend pt. But hopefully are close. This is the titration error.

Volumetric Analysis - Main equipments Burets Burets are graduated tubes holding from 50 -100 milliliters of solution. The solution is released from the Buret through a Teflon stopcock at the bottom. Burets in some labs can be read to the nearest 0.01 milliliter (last digit is estimated (interpolated). Although estimated, it is still significant. The level of fluid in the buret is read from the curved bottom (Meniscus) of the liquid surface.

Burets Burets need not be filled to the top. The volume delivered is the difference in the two readings. Be sure the tip at the bottom of the buret does not have any air bubbles. When titrating, practice is necessary to deliver a single drop of solution, to produce the equivalence point, i.e., neutralization, the point where the indicator changes color permanently.

Titration Process (generalized)‏ Set up two Burets Note: Burets can be read to 0.01 mL (interpolate last digit)‏ Fill one Buret with acid solution; fill the other Buret with the base solution. Read level of liquid (at the meniscus) in each Buret to the nearest 0.01 mL. Deliver required volume of base (~20 mL) to small Erlenmeyer flask. Read final liquid level in Buret containing base solution. Compute volume (to nearest 0.01 mL) of base solution added to flask. Add 1-2 drops of indicator (Phenolphthalein) to Erlenmeyer flask; swirl mixture. Color is vivid pink.

Titration Process (contd)‏ Deliver acid to flask in increments of 1-2 mL, swirling flask after each addition. Reduce volume of acid being added to drops when solution in flask shows signs of changing color. Note: If solution does not return to pink color after swirling, then the titration has gone too far. From buret containing the Base, titrate additional base into flask until color returns to pink. Note: Total base added is the sum of the original amount added and the incremental amount added. If solution color returns to pink after swirling, continue adding the acid, drop by drop, until a single drop results in a permanent colorless solution. Record final liquid levels in Burets and compute volumes of acid and base titrated (to the nearest 0.01mL).

Summary of Volumetric Methods: determining the amount of substance A by adding a carefully measured volume of a solution with a known concentration of B until the reaction of A and B is just complete. A B A+B