You have a bottle of 20% NaOH. You will use some of it to make a new solution by dilution with water. How musch 20% NaOH is needed to prepare 150mL of 7% NaOH by dilution.
To determine how much 20% NaOH is needed to prepare 150mL of 7% NaOH by dilution, we need to consider the relationship between the concentrations, volumes, and amount of solute.
Let's break down the problem step-by-step:
Step 1: Determine the amount of NaOH needed for the final solution.
The final solution will be 150mL in volume and have a concentration of 7% NaOH. To find the amount of NaOH needed, we can multiply the final volume (in milliliters) by the desired concentration (as a decimal):
Amount of NaOH = Volume of solution * Concentration of NaOH
= 150 mL * 0.07
= 10.5 mL
Therefore, we need 10.5 mL of NaOH for the final solution.
Step 2: Calculate the concentration of the 20% NaOH.
A 20% NaOH solution means that there are 20 grams of NaOH per 100 milliliters of solution (or 20g/100mL). We need to convert this to a ratio of grams per milliliter to match the units we have for the final solution.
Concentration of 20% NaOH = (20g / 100mL) = 0.2 g/mL
Step 3: Calculate the volume of the 20% NaOH needed for the final solution.
Since the concentration of the 20% NaOH is given as grams per milliliter, we can use the formula:
Volume of NaOH needed = Amount of NaOH (in grams) / Concentration of NaOH (in g/mL)
Plugging in the values:
Volume of NaOH needed = 10.5 mL / 0.2 g/mL
= 52.5 mL
Therefore, you will need 52.5 mL of 20% NaOH to prepare 150 mL of 7% NaOH by dilution.