Describe how you can prepare 0.25 molar solution of sodium hydroxide from an 80 percent stock solution in a 500mls beaker
80% what. I presume you mean 80% w/v .
80% w/v solution NaOH means 80 g NaOH/100 mL solution. mols NaOH in 80g is mols = grams/molar mass = 80/40 = 2 mols. 2 mols/100 mL solution = 2mol/0.1L = 20 M
mL1 x M1 = mL2 x M2
500mL x 0.25M = mL2 x 20
Solve for mL2, place that amount of the stock solution in a 500 mL volumetric flask and make to the mark. Mix thoroughly.
To prepare a 0.25 molar solution of sodium hydroxide from an 80 percent stock solution, you will need to dilute the stock solution with water. Here's a step-by-step guide on how to do it in a 500 ml beaker:
1. Determine the volume of the 80 percent stock solution needed to make the desired concentration. In this case, you want to make a 0.25 molar solution, so you need to calculate the moles of sodium hydroxide required. You can use the formula:
Moles = Molarity × Volume (in liters)
Rearranging the formula, Volume (in liters) = Moles / Molarity
Since you want to make a 0.25 molar solution and have a 500 ml beaker (which is 0.5 liters), you need to calculate the moles required. Let's assume you want to make 500 ml (0.5 liters) of the solution.
Moles = 0.25 mol/L × 0.5 L = 0.125 moles
2. Calculate the volume of the 80 percent stock solution needed to obtain the desired moles of sodium hydroxide. To find this, you'll need to know the molarity of the stock solution. Let's assume the stock solution has a molarity of 2 M.
Volume of stock solution = Moles / Molarity
Volume = 0.125 mol / 2 mol/L = 0.0625 L or 62.5 ml
So, you need 62.5 ml of the 80 percent stock solution.
3. Measure 62.5 ml of the 80 percent stock solution using a graduated cylinder or a pipette and place it into the 500 ml beaker.
4. Add distilled water to the beaker to bring the total volume up to 500 ml. Make sure to mix the solution thoroughly using a stir rod to ensure uniformity.
5. Once you have reached the desired volume, your 0.25 molar sodium hydroxide solution is ready. You can now use it for your intended purpose.
Remember to handle sodium hydroxide with caution as it can be caustic and can cause burns. Be sure to wear appropriate protective equipment, such as gloves and goggles, and work in a well-ventilated area.