Which of the following negative ions would be the strongest base?
(a) Cl2CHCO2- (Cl2CHCOC2H: Ka = 7.8 x 10-3)
(b) ClCH2CO2- (ClCH2CO2H: Ka = 1.4 x 10-3)
(c) HCO2- (HCO2H: Ka = 1.8 x 10-4)
(d) CH3CO2- (CH3CO2H: Ka = 1.8 x 10-5)
Chemistry · Sun Jul 10 2022
Answered on
The strength of a base is determined by its ability to accept a proton (H+ ion) from a water molecule. The stronger the base, the more readily it can accept a proton. In this case, we can determine the strength of the negative ions by comparing the acidity constants (Ka) of their corresponding acids.
The higher the Ka value, the stronger the acid, and consequently, the weaker its conjugate base. This means that a stronger acid will have a weaker conjugate base.
So, to determine the strongest base among the given options, we need to compare the Ka values of the corresponding acids.
(a) Cl2CHCOC2H: Ka = 7.8 x 10-3 (b) ClCH2CO2H: Ka = 1.4 x 10-3 (c) HCO2H: Ka = 1.8 x 10-4 (d) CH3CO2H: Ka = 1.8 x 10-5
Based on these values, we can see that option (d) CH3CO2- has the highest Ka value for its corresponding acid (CH3CO2H). This means that CH3CO2H is the strongest acid among the given options, and consequently, CH3CO2- is the strongest base among the negative ions provided.
Acids and bases are fundamental concepts in chemistry. Acids are substances that release H+ ions when dissolved in water, while bases are substances that accept H+ ions. The strength of an acid or base is measured by its acidity constant (Ka) or its basicity constant (Kb), respectively.
In this question, we are comparing the strength of negative ions (conjugate bases) based on the acidity constants (Ka) of their corresponding acids. A strong acid will have a high Ka value and a weak conjugate base.
To better understand the concept, it's helpful to look at the molecular structure of the acids and their corresponding conjugate bases. The more stable the conjugate base, the weaker the acid will be. Stability can be influenced by factors such as electronegativity and resonance effects.
In this case, we can see that CH3CO2H (acetic acid) has the highest Ka value, indicating that it is the strongest acid among the given options. As a result, its conjugate base, CH3CO2-, is the strongest base.
It's important to note that this comparison is specific to the given options and their associated Ka values. In a broader context, there can be other variables to consider, such as solvent effects and molecular structures.