What is the definition of a common ion as it applies to Le Chatelier’s principle?
2 answers:
Answer: D) an ion that is present in an equilibrium system and a compound added to the system
Explanation: Any change in the equilibrium is studied on the basis of Le-Chatelier's principle.
This principle states that if there is any change in a equilibrium reaction, the equilibrium will shift in a direction so as to minimize the effect.
Thus when a common ion is introduced to an equilibrium reaction, the equilibrium will shift in a direction where the concentration of common ion is decreasing.
For example: In a equilibrium reaction for dissociation of acetic acid:
If HCl is introduced wth as common ion.
The equilibrium will shift in backward direction where the concentration of is decreasing.
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Answer:
Indicators show changes in the pH of a solution
Explanation:
A pH meter is an instrument that measures the hydrogen-ion activity in aqueous solutions, indicating the acidity or alkalinity of the solution expressed as pH .The pH meter measures the difference in electrical potential between a pH electrode and a reference electrode, hence the pH meter is sometimes referred to as a potentiometric pH meter. Potentiometric pH meters measure the voltage between two electrodes and display the result converted into the corresponding pH value. The instrument comprises of a simple electronic amplifier and a pair of electrodes, or alternatively a combination electrode, and some form of display calibrated in pH units. It usually has a glass electrode and a reference electrode, or a combination electrode. The electrodes, or probes, are inserted into the solution to be tested.
Organic indicators are chemical species that change their colour in response to changes in the pH of the solution. This implies that the anionic and protonated forms of the indicator possess different colours. Hence the colour changes in acidic, basic and neutral solutions. The images attached indicate the colour changes in phenolphthalein and methyl orange in acidic and basic media accordingly.
