Chemistry: Redox titration experiment

CHEMISTRY DESIGN
Determining the equilibrium of a reaction
Caterina Rende Dominis 3mm
Teacher: Zrinka Toplićan
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Iron (III) Thiocyanate Solution:
Fe3+(aq) + SCN−(aq)  Fe(SCN)−(aq)
(pale yellow)  (colorless)           (deep red)

Aim
Determining the equilibrium shift in the above stated reaction by observing the shifts in color when adding Fe(NO3)3 (aq), KSCN (aq) , K2HPO4 (aq) and when changing the temperature, and consequently finding out the equilibrium change.
Hypothesis
Due to the addition of certain chemicals or the change in temperature we will be able to observe the color changes that occur, and by that determine which chemical (aka temperature change) will shift the equilibrium to which side (by examining the connection of the original colors with the ones we obtain: for example addition of Fe(NO3)3 (aq) will most likely turn the color of the solution into yellow, which will cause a shift of the equilibrium to the left.


Variables
Independent variable:
Temperature
Addition of Fe(NO3)3 (aq), KSCN (aq) , K2HPO4 (aq)
Dependent variable:
Change in color of the equilibrium (either yellow or red)
Controlled variable:
Time
Amount of Fe(NO3)3 (aq), KSCN (aq) , K2HPO4 (aq) added  2ml
Controlled Sample
Pressure

Materials:
0.1 M Fe(NO3)3 (aq)
0.1 M KSCN (aq)
0.1 M K2HPO4 (aq)
Ice
Test Tube Rack
5 Test Tubes
Bowl (aka large beaker)
Iron (III) thiocyanate

Procedure
Steps:
Prepare the five test tubes and place them in a rack; put 2 mL of the iron (III) thiocyanate solution into 4 small test tubes. Label these test tubes 1 to 5. Record the initial color.
Test tube number 5 will be untouched during the experiment as this is the controlled sample.
Add 2 mL of 0.1 M of Fe(NO3)3 (aq) to test tube 1. Wait for 10 min, then record your observations in the given table
Add 2 mL of 0.1 M of KSCN (aq) to test tube 2. Wait for 10 min , then write the observations in the table
Add 2 mL of 0.1 M of K2HPO4 (aq) to test tube 3. Wait for 10 min, then record your observations.
Place test tube 4 in a beaker (bowl) full of ice. Wait until a distinct change occurs. Be patient. After waiting write your observations in your table

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Table

Test tube Procedure Color change Favored Reaction  
1 Addition of Fe(NO3)3 (aq)  
2 Addition of KSCN(aq)  
3 Addition of K2HPO4 (aq)  
4 Placing in ice  
5 Original Iron (III) Thiocyanate Solution

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