Describe how to prepare each solution from the dry solute and the solvent. b. 125 g of 0.100 m NaNO₃

Verified step by step guidance

1. <Step 1: Understand the problem.> Determine that you need to prepare a solution with a specific molality (0.100 m) using sodium nitrate (NaNO₃) as the solute and water as the solvent. Molality is defined as moles of solute per kilogram of solvent.
2. <Step 2: Calculate the moles of solute needed.> Use the formula for molality: \( m = \frac{\text{moles of solute}}{\text{kilograms of solvent}} \). Rearrange to find moles of solute: \( \text{moles of solute} = m \times \text{kilograms of solvent} \).
3. <Step 3: Determine the mass of the solvent.> Since the problem specifies 125 g of solution, you need to find the mass of the solvent (water). Assume the mass of the solute is negligible compared to the solvent for this calculation, or adjust based on the solute's mass if needed.
4. <Step 4: Calculate the mass of NaNO₃ needed.> Use the molar mass of NaNO₃ to convert moles of solute to grams. The molar mass of NaNO₃ is approximately 85 g/mol. Use the formula: \( \text{mass of NaNO₃} = \text{moles of NaNO₃} \times \text{molar mass of NaNO₃} \).
5. <Step 5: Prepare the solution.> Weigh the calculated mass of NaNO₃ and dissolve it in the calculated mass of water to achieve the desired molality. Ensure thorough mixing to achieve a homogeneous solution.

Key Concepts

Molarity

Molarity (M) is a measure of concentration defined as the number of moles of solute per liter of solution. It is crucial for preparing solutions, as it allows chemists to quantify how much solute is needed to achieve a desired concentration. In this case, a 0.100 M solution of NaNO3 means there are 0.100 moles of NaNO3 in every liter of the final solution.

Calculating Moles

To prepare a solution, it is essential to calculate the number of moles of solute required. The number of moles can be determined using the formula: moles = mass (g) / molar mass (g/mol). For NaNO3, the molar mass is approximately 85 g/mol, so to find out how many moles are in 125 g, one would divide 125 g by 85 g/mol.

Dilution and Solution Preparation

Preparing a solution involves dissolving the calculated amount of solute in a specific volume of solvent. For a 0.100 M NaNO3 solution, after determining the required moles from the mass, the solute should be added to a volumetric flask with a portion of solvent, mixed until dissolved, and then diluted to the final volume with additional solvent to ensure the correct concentration.