A sample of 8 grams of NaOH is dissolved into 599 mL of aqueous 0.250 M NaOH (assume
no volume change). This solution is then
poured into 1.68 gallons of water. (You may
assume that the two volumes can be added.)
What is the concentration of NaOH in the
final solution?
Answer in units of M
What volume of ethanol must be diluted with
water to prepare 674 mL of 0.854 M solution?
The density of ethanol is given as 0.789 g/mL.
Answer in units of mL
post #1.
Work with mols.
mols NaOH in 8g = grams/molar mass = ?
mols NaOH in 599 mL of 0.250M = M x L = ?
Total mols NaOH = ?
Now total volume is
599 mL + 1.68 gallons. Convert mL to L and convert 1.68 gallons to L. Add to find total L.
Then (NaOH) in final solution is mols/L
To find the concentration of NaOH in the final solution, we need to calculate the total moles of NaOH before and after mixing.
1. First, let's calculate the number of moles of NaOH in the 8 grams of solid NaOH. We can use the molar mass of NaOH to convert grams to moles:
Molar mass of NaOH = 22.99 g/mol (atomic mass of Na) + 16.00 g/mol (atomic mass of O) + 1.01 g/mol (atomic mass of H)
= 39.99 g/mol
Number of moles of NaOH = mass / molar mass
= 8 g / 39.99 g/mol
2. Next, let's calculate the number of moles of NaOH in the 599 mL of 0.250 M aqueous NaOH solution. The concentration (molarity) of a solution is defined as moles of solute per liter of solution:
Concentration (M) = moles / volume (in liters)
= (0.250 moles/L) * (0.599 L)
3. Now we can calculate the total moles of NaOH. Since the volume of the solid NaOH and the aqueous NaOH solution does not change when mixed, we add the number of moles calculated in step 1 and step 2:
Total moles of NaOH = moles from solid NaOH + moles from aqueous NaOH solution
4. Finally, we convert the volume of water from gallons to liters:
1.68 gallons * (3.78541 L/gallon)
5. The concentration of NaOH in the final solution is given by:
Concentration (M) = total moles / total volume (in liters)
By following these steps, you can calculate the concentration of NaOH in the final solution.