Question

What is the conjugate acid of \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\) ? of \(\mathrm{NO}_{3}^{-}\) ?

Short answer

\(\mathrm{H}_{3} \mathrm{PO}_{4}\) is the conjugate acid of \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\), and \(\mathrm{HNO}_{3}\) is the conjugate acid of \(\mathrm{NO}_{3}^{-}\).

Step-by-step solution

Identify the Base

For the given ions, \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\) and \(\mathrm{NO}_{3}^{-}\), begin by confirming their role as a base. A base is a species that can accept a proton (\(\mathrm{H}^{+}\)). In both cases, the ions provided are in a state that can accept a proton.

Add a Proton to the Base

To find the conjugate acid, add a proton (\(\mathrm{H}^{+}\)) to each base:1. \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-} + \mathrm{H}^{+} \rightarrow \mathrm{H}_{3} \mathrm{PO}_{4}\)2. \(\mathrm{NO}_{3}^{-} + \mathrm{H}^{+} \rightarrow \mathrm{HNO}_{3}\)

Determine the Conjugate Acids

From the above reactions, identify the resulting species after addition of the proton. - The conjugate acid of \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\) is \(\mathrm{H}_{3} \mathrm{PO}_{4}\).- The conjugate acid of \(\mathrm{NO}_{3}^{-}\) is \(\mathrm{HNO}_{3}\).

Key concepts

Conjugate Acid

In acid-base chemistry, the concept of a conjugate acid is key for understanding how substances behave in reactions. When a base accepts a proton, it transforms into its conjugate acid. This transformation is vital for maintaining chemical balance.

Consider the example of \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\) and \(\mathrm{NO}_{3}^{-}\). Both of these ions can act as bases because they have the capacity to accept a proton.

• When \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\) accepts a proton, it becomes \(\mathrm{H}_{3} \mathrm{PO}_{4}\), which is its conjugate acid.
• Similarly, \(\mathrm{NO}_{3}^{-}\) becomes \(\mathrm{HNO}_{3}\) upon accepting a proton, turning into its conjugate acid.

Identifying conjugate acids helps predict how substances will interact in their environment. This understanding allows for better control of reactions, particularly in chemical manufacturing and biological systems.

Proton Transfer

Proton transfer is a fundamental concept in acid-base reactions. It involves the movement of a proton (\(\mathrm{H}^{+}\)) from one species to another. This movement underscores countless reactions in chemistry.

The transfer of protons is the defining action of what constitutes acids and bases:

• A base is a proton acceptor, capable of gaining a hydrogen ion.
• An acid is a proton donor, releasing a hydrogen ion into the surroundings.

When \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\) accepts a proton, it undergoes a proton transfer process, showcasing its basic nature.
Understanding this transfer helps in visualizing how reactions balance and how substances transform, enhancing our predictive abilities in various chemical processes.

Chemical Equilibrium

Chemical equilibrium is an essential concept when studying reactions like proton transfer in acid-base systems. It describes a state where the concentrations of reactants and products no longer change with time. In essence, forward and reverse reactions occur at equal rates.

In the context of acid-base chemistry, equilibrium explains how acids and bases reach stability. Consider the reaction:\[\mathrm{H}_{2} \mathrm{PO}_{4}^{-} + \mathrm{H}^{+} \rightleftharpoons \mathrm{H}_{3} \mathrm{PO}_{4}\]The equilibrium state of this reaction shows the balance between the deprotonated base (\(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\)) and its protonated conjugate acid (\(\mathrm{H}_{3} \mathrm{PO}_{4}\)).

• Equilibrium establishes that not all of the base will be converted to its conjugate acid, allowing for a dynamic balance.
• This concept helps chemists understand reaction resilience and predict how systems will respond to changes in environment or conditions.

Thus, equilibrium works as a guiding principle in exploring how chemical systems behave and adapt.