What is the mole fraction of NaOH in an aqueous solution that contains 16.9% NaOH by mass?
molefraction: moles of NaOH/totalmoles
Assume 1000 total grams. Then 169 grams of NaOH, figure the moles of that. Also, figure the moles of 931 grams of water.
molefraction: molesNaOH/(molewater+molesNaOH)
To find the mole fraction of NaOH in the solution, we need to calculate the amount of NaOH and the total amount of solute.
First, calculate the amount of NaOH in grams using the percent by mass:
mass of NaOH = percent by mass × mass of solution
= 16.9% × mass of solution
Next, calculate the amount of water (or solvent) in grams:
mass of water = mass of solution - mass of NaOH
To find the number of moles of NaOH, divide the mass of NaOH by its molar mass. The molar mass of NaOH can be calculated as follows:
molar mass of NaOH = (atomic mass of Na) + (atomic mass of O) + (atomic mass of H)
Once you have the moles of NaOH and the moles of water, you can calculate the mole fraction using the formula:
mole fraction of NaOH = moles of NaOH / (moles of NaOH + moles of water)
Now let's plug in some example values to solve this problem:
Let's assume we have 100 grams of the solution.
mass of NaOH = 16.9% × 100 grams = 16.9 grams
mass of water = 100 grams - 16.9 grams = 83.1 grams
The molar mass of NaOH is approximately 40 grams/mol for Na, 16 grams/mol for O, and 1 gram/mol for H, giving us molar mass of NaOH ≈ 40 + 16 + 1 = 57 grams/mol.
Now we can calculate the number of moles:
moles of NaOH = mass of NaOH / molar mass of NaOH
= 16.9 grams / 57 grams/mol
moles of water = mass of water / molar mass of water
= 83.1 grams / molar mass of water
Finally, use the mole fraction formula:
mole fraction of NaOH = moles of NaOH / (moles of NaOH + moles of water)
By substituting the calculated values, you will get the mole fraction of NaOH in the solution.