Conductometric and Gravimetric Determination

Conductometric and Gravimetric Determination

Purpose: The purpose is to monitor conductivity of a run between H2SO4 and Ba(OH)2 to determine the equivalence point. The reaction makes a solid, BaSO4, which can also be used to determine the original concentration of Ba(OH)2.

Hypothesis: If the equivalence point between H2SO4 and Ba(OH)2 can be determined then the concentration of Ba(OH)2 can be calculated. Also, if the mass of the product between H2SO4 and Ba(OH)2, BaSO4, then the concentration can be calculated.

Materials:

Vernier conductivity probe

Barium hydroxide solution

0.5 sulfuric acid solution

Distilled water

Two 250 mL beakers

50 mL graduated cylinder

Aspirator

10 mL pipet and pipet bulb

Hot plate

Ring stands

Utility clamp

Ring stand ring

Filter paper

Magnetic stirring rod

Filter funnel

Balance +0.01

Stir station

Drop counter

60 mL reagent reservoir

150 mL beaker

10 mL graduated cylinder

Procedures: 1) Use pipette to transfer 15 mL of Ba(OH)2 into a 150 mL beaker, add 60 mL of distilled water.

2) Measure out approximately 60 mL of 2.0 M H2SO4 into a 250 mL beaker (record precise H2SO4 concentration in data table.)

3) Make sure drop counter is calibrated (as instructed).

4) Place 150 mL beaker with Ba(OH)2 Solution under drop counter, conductivity probe and micro-stirrer.

5) Adjust position and check with instructor before starting titration.

6) Conduct Titration:

Click Collect to monitor conductivity.

Fully open bottom valve (top valve should be adjusted so drops are released at a rate of 1 drop every 2 seconds).

The conductivity will drop below 100 uS, then rise again. The titration curve will be v shaped. When conductivity reaches 1000 uS, click stop and turn valve to closed ( horizontally).

7) Examine graph and take photo:

Find equivalence point (the volume when the conductivity reaches a minimum).

Interpolate and move cursor to examine data ( find volume conductivity for each data point).

Record H2SO4 volume of the point with minimum conductivity value.

Take photo of graph and send to instructor as well as yourself.

8) Filter and measure BaSO4:

Warm beaker with BaSO4 precipitate (near boiling for about 5 minutes).

While heating, set up ring stand and ring for Buchner Funnel.

Measure mass of fine-grade filter paper (to the 0.01 place), record in data table.

Allow mixture to cool and the filter it with Buchner Funnel (wash out precipitate with distilled water and pour through funnel).

Dry the precipitate and filter paper as instructed by instructor.

9) Rinse conductivity sensor with distilled water and conduct 2-7 more trails (depending on time).

Data:

Trial 1

Trial 2

Equivalence point (mL)

50 uS/cm

*3.679 mL*

70 uS/cm

*16.929 mL*

Mass of Precipitate + paper (g)

0.773 g

0.700 g

Mass of Filter Paper (g)

1.472 g

0.480 g

Mass of Precipitate (g)

...