Explain how to prepare a solution of a specific molarity concentration, starting witha a dry solute
The correct answer and explanation is:
Correct Answer:
To prepare a solution of a specific molarity (M) using a dry solute, follow these steps:
- Calculate the amount of solute needed using the formula: Mass (g)=M×V×Molar Mass\text{Mass (g)} = M \times V \times \text{Molar Mass} Where:
- MM = desired molarity (mol/L)
- VV = volume of solution in liters (L)
- Molar Mass = molar mass of the solute in grams/mole (g/mol)
- Weigh the solute using a balance, according to the calculated mass.
- Dissolve the solute in a small volume of distilled water (less than the final desired volume) in a beaker or volumetric flask.
- Transfer the solution to a volumetric flask if not already using one.
- Add distilled water up to the calibration mark of the volumetric flask to reach the desired final volume.
- Mix thoroughly to ensure the solute is fully dissolved and evenly distributed.
300-Word Explanation:
Molarity (M) is a measure of concentration, defined as moles of solute per liter of solution. To prepare a solution with a specific molarity, you need to determine the precise amount of solute (in grams) required and dissolve it in enough solvent to reach the target volume.
First, calculate the mass of solute needed. For example, to make 1.00 L of a 0.50 M sodium chloride (NaCl) solution, multiply the molarity (0.50 mol/L) by the volume (1.00 L) and the molar mass of NaCl (58.44 g/mol): 0.50 mol/L×1.00 L×58.44 g/mol=29.22 g0.50 \, \text{mol/L} \times 1.00 \, \text{L} \times 58.44 \, \text{g/mol} = 29.22 \, \text{g}
You would then weigh out 29.22 g of NaCl.
Next, dissolve this solute in a small amount of distilled water. Use less water than the final volume to allow space for dilution. Once the solute is completely dissolved, transfer it to a volumetric flask, and rinse any remaining solution into the flask with distilled water.
Finally, fill the flask with distilled water up to the 1.00 L mark and mix thoroughly. This ensures uniform concentration throughout the solution. This step-by-step process ensures accuracy in chemical preparation, which is essential for reproducibility and safety in scientific experiments.