Slide 1

Report
Le Chatelier’s Principle: When a stress is applied to an
equilibrium, the equilibrium will shift to alleviate the stress.
Fe+3 (aq) + SCN-1 (aq) ⇋ FeSCN+2 (aq)
Colorless
Left shift =
lighter color
⇋
Dark red
Right shift =
darker color
Initial color
Other ways to cause a Le Châtelier Shift:
3 H2 (g) + N2 (g) + heat ⇋ 2 NH3 (g)
What kind of shift would you see if:
Pressure increased?
Right shift 
Volume increased?
 Left shift
Heating temperature increased?
Right shift 
CH4 (g) + 2 Cl2 (g) ⇋ CCl4 (g) + 2 H2 (g) + heat
What kind of shift would you see if:
Pressure increased?
Heating temperature increased?
No Change
 Left shift
Indicators:
• Indicators are organic dyes that are also weak acids or
weak bases.
• The color of the dye depends upon the pH of the solution.
• The indicator will change colors at the pH that corresponds
to its own equivalence point.
• Therefore, it is important to pick an indicator that changes
color very close to the pH at the equivalence point for the
titration.
• Since the color change does not exactly match the
equivalence point, it is called the ENDPOINT of the
titration.

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