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?

Short answer

To prepare 0.250 L of a 0.100 M sodium oxalate \(\left(\mathrm{Na}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\right)\) solution, 3.35 g of sodium oxalate is needed.

Step-by-step solution

Calculate the number of moles of sodium oxalate required

To calculate the number of moles of sodium oxalate required for a 0.100 M solution, we can use the formula: Moles (n) = Molarity (M) x Volume (L) The molarity is given as 0.100 M, and the volume is given as 0.250 L. Plug in these values and solve for the number of moles of sodium oxalate: n = 0.100 M x 0.250 L = 0.025 moles

Calculate the molar mass of sodium oxalate

To find the mass of sodium oxalate needed, we need to know the molar mass of sodium oxalate. Sodium oxalate is Na2C2O4, so its molar mass can be calculated by summing the molar masses of the individual elements: Molar mass of Na2C2O4 = 2(Mass of Na) + 2(Mass of C) + 4(Mass of O) Using the atomic masses from the periodic table: Molar mass of Na2C2O4 = 2(22.989 g/mol) + 2(12.011 g/mol) + 4(16.000 g/mol) = 133.998 g/mol

Find the mass of sodium oxalate needed

Now that we have both the number of moles required and the molar mass of sodium oxalate, we can find the mass of sodium oxalate needed to prepare the solution. Mass = Moles x Molar mass Plug in the number of moles (0.025 moles) and the molar mass (133.998 g/mol) of sodium oxalate: Mass = 0.025 moles x 133.998 g/mol = 3.34995 g

Round to an appropriate number of significant figures

Since the volume and molarity in the question are given to three significant figures, we'll round our answer to three significant figures as well: Mass of sodium oxalate needed = 3.35 g To prepare 0.250 L of a 0.100 M sodium oxalate solution, 3.35 g of sodium oxalate is needed.

Key concepts

Molarity

Molarity is a measure of the concentration of a solute in a solution. It expresses how many moles of a substance are present in one liter of solution. This is an important concept because it helps us understand the strength of solutions, which is crucial in various scientific and industrial applications.

To calculate molarity, you use the formula:

• Molarity (M) = Moles of solute / Volume of solution in liters

For example, if you have 0.025 moles of a solute in 0.250 liters of a solution, the molarity would be 0.100 M. This means there are 0.100 moles of the solute per liter.
Understanding molarity allows scientists and chemists to predict how a solution might behave in reactions. Adjusting molarity can change the properties of a solution, making it more or less reactive.

Sodium Oxalate

Sodium oxalate, represented by the chemical formula \(\text{Na}_2\text{C}_2\text{O}_4\), is a salt derived from oxalic acid. It commonly appears as a white crystalline powder. Sodium oxalate is often used in analytical chemistry as a primary standard for calibrating instruments, due to its stable properties.

When you dissolve sodium oxalate in water, it dissociates into sodium ions (\(\text{Na}^+\)) and oxalate ions (\(\text{C}_2\text{O}_4^{2-}\)). This dissociation is essential for many reactions, especially in biological systems and various industrial processes.

• Sodium oxalate is involved in precipitating reactions in qualitative inorganic analysis.
• It can act as a reducing agent in redox reactions.

Understanding the properties and uses of sodium oxalate helps in leveraging its role in both laboratory settings and industrial controls.

Molar Mass

The molar mass of a compound is the mass of one mole of its constituent particles, usually atoms or molecules. It is expressed in grams per mole (g/mol) and is a crucial factor in chemical calculations.

To find the molar mass of a compound like sodium oxalate (\(\text{Na}_2\text{C}_2\text{O}_4\)), you sum up the atomic masses of all the elements within it. This involves looking up each element's molar mass in the periodic table and multiplying it by the number of atoms of that element in the formula. For sodium oxalate:

• Molar mass of sodium oxalate = 2(22.989 g/mol for Na) + 2(12.011 g/mol for C) + 4(16.000 g/mol for O)
• This adds up to approximately 133.998 g/mol.

Knowing the molar mass is essential for converting between moles and grams, enabling you to prepare solutions and perform reactions accurately. For example, if you know the molar mass and the number of moles needed, you can calculate the exact mass required to make a specific concentration of a solution.