After calculating the mass of NaOH to make the approximate 0.2mol/L solution, why is it not crucial to weigh out an exact amount?
Can't you vary the volume of solution? Measuring out an amount of solute is much easier than measuring out a specific mass.
In addition to the answer by Bob Pursley, we also recognize that NaOH is not a pure substance (at least not for very long) as it pickes up CO2 and H2O from the atmosphere.
When preparing a solution, it is usually not crucial to weigh out an exact amount of solute because the concentration of the solution is more important than the actual mass of the solute. In the case of preparing an approximate 0.2 mol/L solution of NaOH, the key factor is achieving the desired molarity or concentration of the solution.
To determine the mass of NaOH required, you need to know the molar mass of NaOH, which is calculated by adding up the atomic masses of sodium (Na), oxygen (O), and hydrogen (H) in the compound. The molar mass of NaOH is approximately 40 g/mol.
To calculate the mass of NaOH needed to prepare a 0.2 mol/L solution, you can use the formula:
Mass = Molarity (mol/L) x Volume (L) x Molar mass (g/mol)
Let's say you want to prepare 1 liter (L) of the solution:
Mass = 0.2 mol/L x 1 L x 40 g/mol
Mass = 8 grams of NaOH
In this case, you would need approximately 8 grams of NaOH to prepare a 0.2 mol/L solution.
However, it is important to note that you don't need to measure exactly 8 grams of NaOH. The approximate amount is acceptable because the concentration of the solution is defined by the ratio of moles of solute (NaOH) to the volume of the solution (in this case, 0.2 mol/L). As long as you are close to the desired molarity, the solution will have the desired concentration.