I-Solubility Product: Acid-Base Volumetric Analysis

Dr. Prem D. SattsangiCopyright © 2009

What is KHT?KHT is short for Potassium Hydrogen Tartarate.It is mono-potassium salt of TARTARIC ACID.It is only slightly SOLUBLE. The “2 OH” groups are “cis” and written on the left side.

The soluble KHT ionizes to give HT- and K+ ionsKsp (KHT) = [K+ ] [HT- ] = ?

#1-A Solubility Product Experiment

Record Room temperature at the top of each experiment

1. Solubility of KHT in presence of a common ion, [K+]

2. Solubility of KHT in distilled water

3. Determination of an Unknown Potassium concentration

#2 Section-1. Solubility of KHT in presence of a common ion, [K+]

Each student will be assigned a concentration of KNO3

from 0.040 M, 0.060, 0.080 M ….to 0.160 M.

PROCEDURE:1. Calculate mass of KNO3 needed to prepare 100

mL of 0.190 M solution. [n = M x V; Atomic masses (K = 39.09, N = 14.01, O = 16.00)]. (= 1.92 g) FW KNO3 = 101.1

2. 0.190 mol x 0.100 L x 101.1 g = 1.92 g 1 L 1 mol

H. it I.

#2b-Preparing solutionWeigh on the table top balance. [+/- 0.03 g]. Add it to the 100 mL Volumetric flask and make it up to the mark using STOCK-KHT saturated solution. POUR SLOWLY through Funnel. AVOID OVER FILLINGStopper securely. Shake by inversion rotation occasionally. Allow time to equilibrate Proceed with Section 2 of the experiment.

#3 Section-2. Solubility of KHT in distilled water, Filtration of saturated KHT

PROCEDURE:

Set up a filtration apparatus. Moisten the filter paper with Saturated KHT solution.

Place a 150/250 mL beaker underneath the funnel. Do not fill the filter paper to the top. Leave ~ 1 cm empty. Allow to filter. As filtration proceeds, add more solution. Filter all of it.

#4 Section-2 Titration in duplicate of the Filtrate

Pipet 25.00 mL of filtrate in 2 150 mL Erlenmeyer flasks A, B. Add 2 drops phenolphthalein and a small magnetic bar. Set to stir gently.Titrate Flask “A” to a faint pink Titrate Flask “B” to a faint pink

CALCULATE SOLUBILITYNaOH + KHT NaKT + H2O0.0412 M ? M____mL 25.00 mL H. it I.

#5 Section-1 Solubility of KHT Filtration of [K+] in KHT(satd.), Titration, and

Calculation

These are exactly the same as done before for Section 1.For the assigned [K+], write, NaOH (mL) and [HT-] on the BLACK BOARD.A manual plot of the graph is due on the next turn.

This graph will be used by you to figure out the [K+] in the U.K.

CALCULATE SOLUBILITYNaOH + KHT NaKT + H2O0.0412 M ? M____mL 25.00 mL

#6 Section-1. Solubility of KHT in Presence of [K+] added

0.03 0.08 0.130.015

0.02

0.025

0.03

0.035

0.04

0.0450000000000001

0.0500000000000001

Solubilty of KHT in presence of [K+]

Series1

Linear (Series1)

[K+] added

So

lub

ilit

y o

f K

HT

[K

HT

]

If the solubility of KHT in presence of (U.K.) = 0.0315 M; [K+] added = 0.081 M

[K+] [KHT] 0.04 0.0436 0.06 0.0382 0.08 0.0362 0.1 0.0313 0.12 0.0252 0.14 0.0205

Data:

Graph will be used for U.K.

#7 Section-3.Determination of an Unknown [K+] Filtration, Titration, and Calculation

A U.K. solution containing KNO3 and KHT (saturated) will be supplied in a 125 mL Erlenmeyer.

Filtration, Titration in duplicate, and

Calculation are exactly the same as done before for Section 1.

RESULT: Extrapolate the Solubility of KHT on the graph to find the [K+] value for the U.K.

A Report is due on the following Lab period.