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Calculating Molarity of 1 Percent Sodium Hydroxide Solution in Chemistry

Understanding the Preparation of 1% Sodium Hydroxide (NaOH) Solution and Its Molarity

Sodium hydroxide (NaOH), commonly known as caustic soda or lye, is a highly versatile and widely used chemical in various industrial applications, household cleaning products, and laboratory settings. One common preparation is a 1% NaOH solution, which is often used in various experiments and as a cleaning agent. This article will delve into the process of preparing a 1% NaOH solution and how to convert this concentration into molarity (M).

What is a 1% NaOH Solution?

A 1% NaOH solution means that there is 1 gram of sodium hydroxide dissolved in a total of 100 mL of solution. The percentage concentration by weight (w/v) is used here, which indicates how many grams of solute are present in a given volume of solution. This type of concentration is particularly useful in laboratory settings where precise measurements are essential for experiments.

Preparing a 1% NaOH Solution

To prepare a 1% NaOH solution, you will need the following materials

- Sodium hydroxide (NaOH) pellets - Distilled or deionized water - A balance to measure the NaOH - A volumetric flask or a graduated cylinder - A stir rod or magnetic stirrer

Here are the step-by-step instructions to prepare the solution

1. Weigh the NaOH Measure out 1 gram of sodium hydroxide pellets using a balance. Be cautious, as NaOH is hygroscopic and can absorb moisture from the air, leading to inaccuracies in measurement if left exposed.

2. Dissolve the NaOH Pour about 80 mL of distilled or deionized water into a clean container (preferably a beaker or a glass flask). Gradually add the 1 gram of NaOH pellets to the water. It is crucial to add the NaOH to water and not the other way around to avoid exothermic reactions that can cause splattering.

3. Stir the Solution Use a stir rod or magnetic stirrer to mix the solution thoroughly until all the NaOH has dissolved completely. You should see a clear solution without any solid residues.

4. Adjust the Volume After the NaOH is fully dissolved, transfer the solution to a volumetric flask or graduated cylinder. Add distilled water until the total volume reaches exactly 100 mL. This step is essential to ensure the solution is at the correct concentration.

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5. Storage Store the prepared 1% NaOH solution in a properly labeled container, preferably made of glass or specific plastic that is resistant to caustic substances.

Calculating Molarity from Percentage Concentration

To convert the 1% NaOH solution into molarity (M), we first need to understand the relationship between grams, molar mass, and liters. The molarity is calculated using the formula

\[ \text{Molarity (M)} = \frac{\text{moles of solute}}{\text{liters of solution}} \]

1. Determine the Molar Mass of NaOH The molar mass of sodium hydroxide (NaOH) is approximately 40 g/mol (23 g/mol for Na, 16 g/mol for O, and 1 g/mol for H).

2. Calculate Moles In a 1% solution, there is 1 gram of NaOH in 100 mL (0.1 L). To find the number of moles

\[ \text{Moles of NaOH} = \frac{1 \text{ g}}{40 \text{ g/mol}} = 0.025 \text{ moles} \]

3. Calculate Molarity

\[ \text{Molarity} = \frac{0.025 \text{ moles}}{0.1 \text{ L}} = 0.25 \text{ M} \]

Thus, a 1% NaOH solution corresponds to a molarity of 0.25 M.

Conclusion

In summary, preparing a 1% sodium hydroxide solution is a straightforward process that requires precise measurements and careful handling, given NaOH's caustic nature. Understanding the molarity of such solutions is crucial for various applications, especially in laboratory environments where reaction conditions must be meticulously controlled. By following the outlined steps and calculations, one can confidently prepare and utilize NaOH solutions for a variety of needs.

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