If a base is added to pure water, why does the [H₃O⁺] decrease?

Question

Accepted Answer

Hello. In this problem, we are asked to explain why. Adding a base to pure water causes the concentration of hydro mines to decrease. We are provided with four possible answers. Answer a states the base reacts with hydro mines forming its conjugate acid. Thus reducing the concentration of acidic hydro mines. B the base reacts with water to form hydro mines. Thus reducing the concentration of hydrogen ions. C the base reacts with hydroxide ions to form more water molecules. And D the base has a higher affinity for hydris than water molecules. Leading to a decrease in the concentration of hydro mines. Recall that water can undergo auto organization. That then means that some water molecules act as an acid and donate a proton and others act as a base by accepting that proton, we then form hydro minds and hydroxide ions and establish an equilibrium. We can therefore write an equilibrium constant expression which is called the iron product, constant of water. It is the concentration of hydrogen ions times the concentration of hydroxid ions. And this is equal to one times 10 to minus 14 at 25 degrees Celsius. And so when we add a base, it will react with the acid component in water. So it will react with the hydro mines, hydronym ions, then will donate a proton to the hydroxid ions. And in doing so, then we will form two molecules of water in forming a molecule of water. Then we are consuming the hydro mines and we are generating then water which is the conjugate acid of our base hydroxide ions. And it is also true that the iron product, constant of water, it remains a constant as long as the temperature remains constant. So that then tells us if the hydroxid ion concentration goes up, the hydro ion concentration must go down. So looking at the answers that we have been provided, we have then answer a states that the base reacts with hydro mines forming its conjugate acid, thus reducing the concentration of acidic hydro mines. So this answer is correct answer B states the base reacts with water to form hydro mines, thus reducing the concentration of hydro mines. So that doesn't make sense that we form hydro mines and also at the same time, reduce the concentration of hydro mines. So that's incorrect. C states that the base reacts with hydroxide ions to form more water molecules. So that's incorrect. And answer D states the base has a higher affinity for hydron nines than water molecules leading to a decrease in the concentration of hydro mines. So the hydroxide reacts with the hydronic mines and thereby gains a proton, but it does not have greater affinity for the hydro nines than water molecules. So answer D is incorrect. So our correct answer is answer. A thanks for watching. Hope this helped.

If a base is added to pure water, why does the [H₃O⁺] decrease?

Watch next