# Chemistry - acids, bases, equilibrium

In summary, acids are substances with a pH less than 7 that can donate protons, while bases have a pH greater than 7 and can accept protons. pH can be calculated using the formula pH = -log[H+], with values less than 7 being acidic and values greater than 7 being basic. Equilibrium in a chemical reaction allows for a stable and balanced system, and temperature can affect equilibrium according to Le Chatelier's principle. A common example of an acid and base reaction is the neutralization between hydrochloric acid and sodium hydroxide to form water and sodium chloride.

## Homework Statement

Like all equilibrium constants, Kw varies somewhat with temperature. Given that Kw is 3.49e-13 at some temperature, compute the pH of a neutral aqueous solution at that temperature.

Kw = [H+][OH-]
pH = -log[H+]

## The Attempt at a Solution

3.49e-13 = [H+]*10e-7
[H+] = 3.49e-6
pH = 5.457

remember Kw is the ionproduct of water at a given temperature. So {H+}*{OH-}= 3.49e-13 next {H+}*{OH-} can be seen as {H+}e2 so what to do next to gain {H+} from Kw?

I would like to point out that the value of Kw does vary with temperature, as mentioned in the statement. This is due to the fact that the ionization of water, which is responsible for the formation of H+ and OH- ions, is an endothermic reaction. As temperature increases, the equilibrium shifts towards the products, resulting in an increase in the concentration of H+ and OH- ions and therefore a higher value of Kw. Similarly, as temperature decreases, the equilibrium shifts towards the reactants, resulting in a decrease in the concentration of H+ and OH- ions and a lower value of Kw.

Based on the given value of Kw, we can calculate the concentration of H+ ions in a neutral aqueous solution at that temperature. Using the equation for Kw, we can rearrange it to solve for [H+]. Plugging in the given value of Kw and assuming that the concentration of OH- ions in a neutral solution is equal to the concentration of H+ ions, we can solve for [H+]. This gives us a value of 3.49e-6 for [H+].

Using the equation for pH, we can then calculate the pH of the neutral solution at that temperature. Plugging in the value of [H+], we get a pH of 5.457. This means that at the given temperature, a neutral aqueous solution would have a pH of 5.457.

It is important to note that this calculation assumes ideal conditions and does not take into account any other factors that may affect the ionization of water, such as the presence of other solutes or changes in pressure. However, it does provide a good estimate of the pH of a neutral solution at the given temperature.

## 1. What is the difference between acids and bases?

Acids are substances that have a pH less than 7 and can donate protons, while bases have a pH greater than 7 and can accept protons. Acids and bases also have different chemical properties and react differently with other substances.

## 2. How do you calculate the pH of an acid or base?

The pH of an acid or base can be calculated using the formula pH = -log[H+], where [H+] is the concentration of hydrogen ions in the solution. The pH scale ranges from 0-14, with 7 being neutral, values less than 7 being acidic, and values greater than 7 being basic.

## 3. What is the purpose of equilibrium in a chemical reaction?

Equilibrium is a state in which the forward and reverse reactions occur at the same rate, resulting in no net change in the concentration of reactants and products. This allows for a stable and balanced system, which is essential for many chemical processes and reactions.

## 4. How does temperature affect equilibrium in a chemical reaction?

According to Le Chatelier's principle, increasing the temperature of a reaction will favor the endothermic reaction and decrease the yield of products. Conversely, decreasing the temperature will favor the exothermic reaction and increase the yield of products.

## 5. Can you give an example of a common acid and base reaction?

One common example of an acid and base reaction is the reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH) to form water (H2O) and sodium chloride (NaCl). This reaction is also known as neutralization and is often used in household cleaning products.

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