In the lab, as acid concentration got decreased, the Ka got increased. Why ?
To understand why the Ka value increases as acid concentration decreases in a laboratory experiment, it's important to know what Ka represents.
Ka, also known as the acid dissociation constant, is a measure of how much an acid disassociates or ionizes in an aqueous solution. It is calculated by dividing the concentration of the products of the dissociation reaction by the concentration of the acid.
In general, a higher Ka value indicates a stronger acid because a larger proportion of the acid molecules dissociate to form ions. Conversely, a lower Ka value indicates a weaker acid because fewer molecules dissociate.
Now, let's consider the scenario where the acid concentration is decreased in the lab. As the acid concentration decreases, there are fewer acid molecules available in the solution. With fewer acid molecules, there is less opportunity for dissociation to occur.
However, since the overall volume of the solution remains constant, the concentration of water (H2O) increases as the acid concentration decreases. Water can act as a base and react with the remaining acid molecules to generate hydronium ions (H3O+). This is described by the equation: H2O + HA โ H3O+ + A-, where HA represents the acid.
Due to the increased concentration of water and the reaction between water and the remaining acid molecules, the relative concentration of the products (H3O+ and A-) increases in relation to the concentration of the acid (HA). As a result, the calculated Ka value increases.
In summary, as the acid concentration decreases in the lab, there is a higher relative concentration of the products of acid dissociation, leading to an increase in the Ka value.