Answer the following in a complete sentence or two: a. How do you know if an acid is strong or weak? b. How do you calculate the pH of a strong acid? c. How do you calculate the pH of a weak acid solution? d. If you know the Ka of an acid, how do you determine the Kb of its conjugate base? e. If you know [OH-] for a solution, how do you determine [H3O+]?

To understand the difference between strong and weak acids, you should consider their ability to dissociate in water. Strong acids such as hydrochloric acid (HCl), sulfuric acid (H2SO4), and nitric acid (HNO3), disassociate completely in water, leaving no original acid molecules behind. This means that the concentration of hydrogen ions () in solution is equal to the initial concentration of the acid. On the other hand, weak acids, like acetic acid (CH3COOH), partially dissociate and establish an equilibrium between the undissociated acid and the ions produced.

To verify if an acid is strong or weak, check its dissociation in water or refer to common lists of known strong and weak acids. Knowing the difference is vital for pH calculations and understanding acid-base reactions.

The acid dissociation constant, or Ka, is a measure of the strength of an acid in solution. It's defined for weak acids, because unlike strong acids that fully dissociate, weak acids do so partially. The Ka value is a ratio that compares the concentration of the produced ions () and () to the concentration of the undissociated acid ().

The expression looks like this:
. High values of Ka imply a stronger acid that dissociates to a greater extent in solution. The smaller the value of Ka, the weaker the acid. Knowing the Ka provides insight into the equilibrium position of the dissociation process and is essential for calculating the pH of a weak acid solution.

When we talk about the conjugate base of an acid, we refer to the species that remains after the acid has donated a proton (H+ ion). The strength of a conjugate base is linked to its proton-accepting ability and is measured by the base dissociation constant, Kb. For a weak acid, its conjugate base is a weak base.

The relationship between Ka for an acid and Kb for its conjugate base is inversely proportional, governed by the equation . This means that if you have the Ka of an acid, you can find the Kb for its conjugate base by dividing the ion product constant of water, Kw, by the Ka value (). This is crucial for understanding the acid-base properties of a solution and for calculating pH when dealing with weak bases.

Hydrogen ion concentration () is a cornerstone of acid-base chemistry and is directly used in the calculation of pH. For strong acids, which fully dissociate, the hydrogen ion concentration is the same as the acid concentration. But for weak acids, you must consider the equilibrium established in the solution, and use the Ka value to find the hydrogen ion concentration.

To calculate the for a weak acid, you would typically set up an equilibrium constant expression using Ka and solve for the concentration of the hydronium ions () using the ICE table method (Initial, Change, Equilibrium). Once you know the , you can then calculate the pH using the formula , which is crucial for understanding the acidity of solutions.

The hydroxide ion concentration () is central to calculations involving bases. In water, the hydroxide and hydronium ion concentrations are related through the ion product constant of water, Kw. When you have the concentration of hydroxide ions, you can calculate the concentration of hydronium ions () using the formula .

At room temperature (25°C), Kw is . If the for a solution is known, the equation allows you to determine the hydronium ion concentration. This is then used to calculate the pH of the solution, providing a measure of its basicity. Understanding is essential for solving many chemistry problems, especially those related to the pH of basic solutions.