Problem 12 - Chemistry An Atoms First Approach

Question

What mass of sodium oxalate \(\left(\mathrm{Na}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\right)\) is needed to prepare \(0.250 \mathrm{L}\) of a \(0.100-M\) solution?

Step-by-Step Solution

Answer

To find the mass of sodium oxalate needed, first calculate the moles of solute: Moles of solute = \(0.100 \mathrm{M} × 0.250 \mathrm{L}\) = \(0.025 \mathrm{mol}\).

Step 1: Find the number of moles required

Use the formula for molarity: Moles of solute = Molarity × Volume of solution Here, the molarity of the solution is \(0.100\) M and the volume of the solution is \(0.250\) L. Calculate the moles of sodium oxalate: Moles of solute = \(0.100 \mathrm{M} × 0.250 \mathrm{L}\)

Key Concepts

Sodium Oxalate

Sodium Oxalate, represented chemically as \( \text{Na}_2\text{C}_2\text{O}_4 \), is a salt consisting of sodium ions and oxalate ions. It is commonly used in the laboratory for various applications such as standardizing potassium permanganate solutions.
Sodium oxalate is characterized by its white color and crystalline appearance. It is slightly soluble in water, which allows it to dissolve and form a solution when mixed with water. This property makes it suitable for preparing standard solutions in titrations and other chemical processes.
Understanding the chemical formula is crucial because it provides insight into the composition and molar mass, which are essential components in solution preparation. This knowledge helps in calculating the amount needed to achieve desired molarity in a given volume.

Solution Preparation

Solution preparation is a fundamental technique in chemistry that involves dissolving a given quantity of a solute in a solvent to form a homogeneous mixture. The goal is to achieve a specific concentration, measured as molarity, which is a crucial parameter for solution use in experiments.
When preparing a solution, it's important to follow these steps:

• Determine the desired molarity and volume of the solution you need.
• Calculate the number of moles of solute required using the formula: \[\text{Moles of solute} = \text{Molarity} \times \text{Volume (L)}\]
• Convert the moles of solute to grams using the molar mass of the solute, which is obtained from the chemical formula.
• Weigh the calculated mass of the solute and dissolve it in the solvent, typically water, to reach the desired volume.

These steps ensure accurate preparation of solutions that are critical for laboratory experiments and research.

Moles of Solute

The concept of moles of solute is an essential part of understanding solution chemistry. Moles provide a bridge between the microscopic world of atoms and the macroscopic world that we encounter daily. One mole contains Avogadro's number of entities, typically atoms or molecules, making it a standard measurement unit in chemistry.
To calculate the moles of solute in a solution, use the relationship between molarity (\( M \)) and volume (\( V \)) with the formula:

• \( \text{Moles of solute} = M \times V \)

Where \( M \) is the molarity, and \( V \) is the volume in liters. This formula is crucial because it allows for the accurate preparation and scaling of chemical reactions.
Knowing how to manipulate the equation is key for tasks like diluting solutions or determining how much solute is needed to reach a specific concentration, as in the original exercise.