Question

Which solution, \(1.0 \mathrm{~m} \mathrm{MgCl}_{2}\) or \(1.0 \mathrm{~m} \mathrm{NaNO}_{3}\), should have the greatest osmotic pressure? Explain.

Short answer

The \(1.0 \mathrm{~m} \mathrm{MgCl}_{2}\) solution should have the greatest osmotic pressure because it dissociates into more particles compared to \(1.0 \mathrm{~m} \mathrm{NaNO}_{3}\).

Step-by-step solution

Identify Relevant Formulas and Principles

The osmotic pressure is determined by the number of solute particles in a solution. Recall that the greater the number of dissolved particles, the greater the osmotic pressure. In this case, \(\mathrm{MgCl}_{2}\) and \(\mathrm{NaNO}_{3}\) are the solutes.

Determine the Dissociation of the Compounds

Dissociation refers to the separation of ions that occurs when an ionic compound dissolves. When \(\mathrm{MgCl}_{2}\) dissolves, it will dissociate into one magnesium ion \(Mg^{2+}\) and two chloride ions \(Cl^{-}\) for a total of three particles. \(\mathrm{NaNO}_{3}\), on the other hand, dissolves into one sodium ion \(Na^{+}\) and one nitrate ion \(NO_{3}^{-}\) for a total of two particles.

Compare the Osmotic Pressures

Considering that osmotic pressure is directly proportional to the number of particles, the \(\mathrm{MgCl}_{2}\) solution has a higher osmotic pressure because it forms more particles when dissolved.

Key concepts

Dissociation

Dissociation is an essential concept in chemistry that refers to the process where ionic compounds separate into their individual ions. When an ionic compound is introduced to a solvent like water, it breaks down into its component ions. This process is crucial because it determines the number of particles that will potently influence properties like osmotic pressure.

For example, when you dissolve magnesium chloride (\( \mathrm{MgCl}_{2} \)), it undergoes dissociation to form one magnesium ion (\( \mathrm{Mg}^{2+} \)) and two chloride ions (\( \mathrm{Cl}^{-} \)). Similarly, sodium nitrate (\( \mathrm{NaNO}_{3} \)) dissolves to form one sodium ion (\( \mathrm{Na}^{+} \)) and one nitrate ion (\( \mathrm{NO}_{3}^{-} \)). This means that the dissociation process results in varying particle amounts between compounds.

Ultimately, understanding the dissociation of ionic compounds provides insight into why different solutions may exhibit different physical properties.

Ionic Compounds

Ionic compounds are a fundamental type of chemical compound comprised of ions held together by ionic bonds. These compounds are typically formed from metals and non-metals. The metal atoms donate electrons to the non-metal atoms, creating positive and negative ions that are strongly attracted to each other.

Some key characteristics of ionic compounds include:

• High melting and boiling points, due to the strong attraction between ions
• Good electrical conductivity when dissolved in water, as the free ions move and carry the current
• They generally dissolve well in polar solvents like water, due to the ability of the solvent to stabilize the ions.

When \( \mathrm{MgCl}_{2} \) dissolves, it yields more ions compared to \( \mathrm{NaNO}_{3} \), illustrating how different ionic compounds can impact the properties of their solutions. Their ability to dissociate into multiple ions dramatically affects factors such as osmotic pressure across solutions.

Solute Particles

In solutions, solute particles refer to the ions or molecules that are dispersed within the solvent. The behavior and quantity of these particles can significantly affect the physical characteristics of a solution, including osmotic pressure. Osmotic pressure is directly proportional to the number of solute particles present in the solution.

Using our previous compounds as examples, \( \mathrm{MgCl}_{2} \) dissociates into three solute particles: one magnesium ion and two chloride ions. In contrast, \( \mathrm{NaNO}_{3} \) dissociates into two particles: one sodium ion and one nitrate ion. This difference in the number of particles explains why \( \mathrm{MgCl}_{2} \) leads to a higher osmotic pressure when dissolved in water.

Understanding solute particles and their count not only helps in predicting osmotic pressure but also plays a vital role in various chemical and biological processes. It helps in unveiling the behavior of solutions, particularly in understanding how they function within different contexts such as cells and chemical reactions.