Which method is NOT used to determine the rate of a reaction?

 Which method is NOT used to determine the rate of a reaction?

A. change in amount of precipitate formed

B. change in equilibrium constant

C. change in intensity of colour

D. change in pH values

E. change in total gas pressure

The correct answer is B. change in equilibrium constant.

Explanation:

The equilibrium constant is not used to determine the rate of a reaction. The equilibrium constant (K) is a measure of the position of equilibrium in a chemical reaction, indicating the relative amounts of reactants and products at equilibrium. It is a constant value for a specific reaction at a specific temperature.

On the other hand, the rate of a reaction measures the speed at which reactants are converted into products. This can be determined by monitoring the change in certain properties of the reaction over time.

 The methods listed in the other options can be used to determine the rate of a reaction as presented below:

Option A: change in amount of precipitate formed :- This involves measuring the amount of solid product (precipitate) formed over time. The rate of a reaction can be determined by calculating the rate at which the precipitate forms.

Option C: change in intensity of colour:-This method is used when the reaction involves a colored substance. The rate of the reaction can be determined by monitoring the change in the intensity of the color over time, using a colorimeter or spectrophotometer.

Option D: change in pH values:- This method is used for acid-base reactions. The rate of a reaction can be determined by measuring the change in pH over time, using a pH meter or indicator like methyl orange or phenolphthalein.

Option E: change in total gas pressure: - This method is used for reactions that involve the production or consumption of gases. The rate of a reaction can be determined by monitoring the change in gas pressure over time.

SOURCE: NECO CHEMISTRY 2001 QUESTION 16