General Inquiry Quiz

A solution of HEPES (a weak acid) and its conjugated base, used to maintain a stable pH in experiments.

The form of a weak acid that has lost a proton (H+).

The concentration of a solution expressed as the number of moles of solute per liter of solution.

A form of energy that travels in waves and includes visible light, infrared radiation, ultraviolet radiation, and other forms.

A particle representing a quantum of light.

The process where a molecule takes in light energy.

A diagram depicting the energy levels within molecules and how electrons move between these levels.

The lowest energy state of a molecule.

The amount of acid or base a buffer can absorb before its pH changes significantly.

A mathematical equation used to calculate the pH of a buffer solution. It relates the pH to the pKa of the weak acid and the ratio of the concentrations of the acid and its conjugate base.

The pH at which a weak acid is 50% ionized and 50% un-ionized.

Buffers minimize changes in pH when small amounts of acid or base are added, not prevent them completely.

The ideal buffer for an experiment has a pKa close to the desired working pH. A good rule of thumb is to choose a buffer with a pKa within 1 pH unit of the working pH.

A buffer's ability to resist changes in pH decreases as the solution's pH moves further away from the pKa of the buffer.

The higher the concentration of a buffer, the greater its buffer capacity.

A measure of how much acid or base (in moles) is required to change the pH of a solution by 1 unit.

The process where a photon's energy is transferred to a molecule, causing an electron to transition to a higher energy level.

The movement of an electron from one energy level to another within a molecule, often caused by photon absorption.

A higher energy state of an electron within a molecule, achieved after absorbing a photon.

A graph showing the wavelengths of light absorbed by a substance, revealing the energy levels within its molecules.

A device that measures the amount of light absorbed by a substance at specific wavelengths.

The component producing the light beam used for absorption measurements, with different types emitting light at different wavelengths.

Process where specific wavelengths of light are chosen for absorption measurements, allowing researchers to study specific transitions within molecules.

To prepare a buffer, dissolve the buffer components (weak acid and conjugate base) to the desired concentration in water. Adjust the pH using a strong acid or base (like NaOH or HCl) until the target pH is achieved.

Calculate the required mass of the weak acid (HA) and conjugate base (A-) forms of the buffer using their molecular weights and desired concentrations. Dissolve these weighed amounts in a specific final volume of water.

Start with a known concentration of either the weak acid (HA) or conjugate base (A-). Use the Henderson-Hasselbalch equation to calculate the required concentration of the other component to achieve the desired pH. Then adjust the volumes of the two solutions to make the total buffer volume.

Begin with a solution of either the weak acid (HA) or conjugate base (A-) and adjust the pH with a strong acid or base (like NaOH or HCl) to reach the desired pH. Dilute the solution to the final volume to obtain the desired buffer concentration.

Rearrange the Henderson-Hasselbalch equation to solve for the ratio of conjugate base (A-) to weak acid (HA). This ratio determines the relative amounts of each component needed for the buffer.

Knowing the total buffer concentration and the A-/HA ratio, you can calculate the individual concentrations of the weak acid (HA) and conjugate base (A-), which then determine the required masses for preparing the buffer.

The equilibrium constant for the autoionization of water, which describes the balance between water molecules and their dissociated ions (H+ and OH-). At 25°C, Kw is 1 x 10^-14.

A solution that resists changes in pH when small amounts of acid or base are added. They typically contain a weak acid and its conjugate base, which work in a pair to neutralize added acid or base.

An acid that does not completely dissociate in a solution. It exists in equilibrium with its conjugate base, meaning it only partially releases protons.

Buffers are crucial for maintaining the pH stability of cells and fluids in biological systems. They prevent drastic pH changes that could damage enzymes, proteins, and other cellular components.