# I need 2.5 mL of a 10% aqueous sodium hydroxide solution. How do I make it?

## Question:

I need 2.5 mL of 10% aqueous sodium hydroxide solution. How do I make it?

## Mass Percent Concentration:

The mass percent concentration is a quantification of the percentage of a solute dissolved in a solution in terms of the mass of each component. Similar to any other percent, it's calculated by dividing a part by the total and then multiplying by 100%. For a solution concentration, the part is the solute and the total is the solution. Therefore, the mass percentage concentration is quantified by dividing the mass of the solute (Plugin insertion failed: Plugin failed) by the mass of the solution (Plugin insertion failed: Plugin failed) and multiplying the result by 100%. This can be represented mathematically as:

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It's important to note that the mass percentage concentration can be calculated using any mass units as long as the same unit is used for each mass. The mass units will cancel out; multiplication by 100% shifts the decimal place by 2 and gives the resulting value a unit of percent.

## Answer and Explanation:

Given:

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To prepare a solution, we need to know:

• The amount of the solute needed
• The amount of the solvent needed, or the total volume or mass required so that the solvent can be added until that point is reached

In this problem the total volume of the solution desired is given, but not any direct information about the amounts of solute or solvent. The mass percent given can be related to the mass of the solute and the mass of the solution using the following equation:

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Although the mass of the solution was not directly given, it can be calculated using the volume of the solution if the density of the solution is known. The density of common solutions, such as this one, can generally be found in tables of densities. For example, a 10% sodium hydroxide (NaOH) solution has a density of 1.11 g/mL.

Using the volume and density of the solution, the mass of the solution is calculated as follows:

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The mass of the solute can be found using the mass percent concentration and the mass of the solution as follows:

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Therefore, this solution can be prepared by combining 0.2775 grams of NaOH with 2.775 grams of water, or by adding enough water to 0.2775 grams of NaOH, which will result in a total volume of 2.5 mL.