Sodium Hydroxide solution?

Question

If I need to prepare a sodium hydroxide solution from solid sodium hydroxide pellets that is approximately 0.2M, how many grams of sodium hydroxide and how many mL of water do I need?

How much KHP do I need to standardize the 1 L solution?

Answer 1

How much of the solution do you need?

Let's assume you want to make 1 L of solution. You'll need 0.2 mol of NaOH.

Since the molar mass of NaOH = 40 g/mol, 0.2 mol X 40 g/mol = 8 g NaOH.

Dissolving 8 g NaOH in enough water to produce 1 L of solution would give you a 0.2 M solution of NaOH.

If you want a different volume, you can just use the 8 g/L and multiply that by the volume (in L) that you want to make.

Answer 2

One uses the moleculkar weight of NaOH to calculate concentration. The molecular weight is the sum of the individual atomic weights. The atomic weights can be found in a periodic table. They are the numbers with decimal points. For NaOH, the molecular weight is 1+15.99+22.99 = 39.98, the weight of 1 mole of Sodium hydroxide. Molarity is expressed in moles/liter, so if a liter is to be prepared, use 0.20 moles. This would 0.20 * 39.98 grams of NaOH in 1 liter of water.

FYI: Sodium hydroxide is unstable because it absorbs atmospheric CO2, forming Sodium carbonate. After the solution is prepared, it is usually titrated with hydrogen pthalate (I think) and phenolphthalien indicator to determine the true molarity. A phthalate solution of known molarity is used to titrate a certain volume of the NaOH solution. The end point of the titration is when the indicator turns bright pink.

Answer 3

A molar (M) of a substance is the number of moles of the substance per liter of solution. This means you have to have 0.2 moles of sodium hydroxide and dissolve it in a liter of solution (1000 mL) to have 0.2M aqueous solution of sodium hydroxide.

the number of grames per mol of NaOH is 39.996 (rounded off to 5SF). Do the math by multiplying this by 0.2 and there you have the amount you needed to dissolve in 1000 mL of solution.

Answer 4

0.2mol/L x 40.0g/mol = 8 g/L