Question

When the ionic solute \(\mathrm{K}_{3} \mathrm{PO}_{4}\) is dissolved in water, what can you say about the number of potassium ions \(\left(\mathrm{K}^{+}\right)\) present in the solution compared with the number of phosphate ions \(\left(\mathrm{PO}_{4}^{3-}\right)\) in the solution?

Short answer

When the ionic solute \(\mathrm{K}_{3} \mathrm{PO}_{4}\) is dissolved in water, it dissociates into its constituent ions. In this case, there are 3 potassium ions (\(\mathrm{K}^{+}\)) for every 1 phosphate ion (\(\mathrm{PO}_{4}^{3-}\)). Therefore, the number of potassium ions in the solution is 3 times greater than the number of phosphate ions.

Step-by-step solution

Understand the given ionic solute

The given ionic solute \(\mathrm{K}_{3} \mathrm{PO}_{4}\) consists of potassium ions (K+) and phosphate ions (PO43-). We can analyze the chemical formula to understand the ratio between the two ions. K has a subscript of 3, meaning that there are 3 potassium ions for every 1 phosphate ion.

Determine the number of potassium and phosphate ions in the solution

When the ionic solute dissolves in water, it dissociates into its constituent ions. This means that for every formula unit of \(\mathrm{K}_{3} \mathrm{PO}_{4}\) , three potassium ions (\(\mathrm{K}^{+}\)) are released and one phosphate ion (\(\mathrm{PO}_{4}^{3-}\)) is released.

Compare the number of potassium ions and phosphate ions

Now that we know that there are 3 potassium ions for every 1 phosphate ion, we can say that the number of potassium ions in the solution is 3 times greater than the number of phosphate ions.

Key concepts

Chemical Formula

The chemical formula of a substance provides invaluable information about its composition. For instance, the formula \(\mathrm{K}_{3}\mathrm{PO}_{4}\), representing potassium phosphate, tells us that each molecule is composed of three potassium (K) atoms and one phosphate (PO4) group. When analyzing a chemical formula, the subscript numbers directly following the chemical symbols indicate the quantity of atoms or ions of that element within one molecule of the compound. If there is no subscript, it means there is only one atom of that element.

Understanding chemical formulas is fundamental in chemistry because it serves as the language that describes the ratio and type of atoms involved in chemical compounds. By examining the formula of potassium phosphate, one can instantly discern the ratio of potassium to phosphate ions present in a molecule, which is essential for predicting how the compound will behave when dissolved in water or reacting with other substances.

Ion Dissociation in Water

When an ionic solute like \(\mathrm{K}_{3}\mathrm{PO}_{4}\) dissolves in water, it undergoes a process known as ion dissociation. This means that the solid compound separates into its individual ions within the solution. Water, being a polar solvent, is exceptionally proficient at this task due to its capacity to surround and stabilize the charged ions, allowing them to move freely in solution.

The dissociation of \(\mathrm{K}_{3}\mathrm{PO}_{4}\) in water results in the release of potassium ions (\(\mathrm{K}^{+}\)) and phosphate ions (\(\mathrm{PO}_{4}^{3-}\)). The degree of dissociation is predicted by the compound's solubility and the stoichiometry of the formula. This dissociation is crucial in various chemical processes, including biological systems, industrial applications, and is a key principle in understanding ionic equilibrium in aqueous solutions.

Stoichiometry of Ions

Stoichiometry is the aspect of chemistry that deals with the quantitative relationships between the substances involved in chemical reactions. In the context of ion dissociation, the stoichiometry of ions refers to the proportions in which the ions are formed from the dissolved ionic compounds. When potassium phosphate dissolves, the stoichiometry of the ions is based on the subscripts in its chemical formula.

This dictates that for every one unit of \(\mathrm{K}_{3}\mathrm{PO}_{4}\) that dissolves, three potassium ions (\(\mathrm{K}^{+}\)) and one phosphate ion (\(\mathrm{PO}_{4}^{3-}\)) will be present in the solution. These ratios are important for calculating concentrations, reaction yields, and in predicting the outcomes of chemical reactions. By mastering the stoichiometry of ions, students can proficiently navigate through chemical equations and solutions chemistry, forecasting the amounts of products and reactants with precision.