A sample of 6.41 grams of NaOH is dissolved into 675 mL of aqueous 0.250 M NaOH (assume no volume change). This solution is then poured into 2.28 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.

Mr. Bob, I got 0.038119 and it's wrong.

Unfortunately you didn't show your work so I can't find the error for you. I expect you converted 2.28 gallons incorrectly (or you may have forgotten to add in the 675 mL to the 2.28 gallons). My answer is 0.03535M which rounds to 0.0354M to three s.f.

To find the concentration of NaOH in the final solution, we need to calculate the number of moles of NaOH in the initial solution, and then calculate the final volume of the solution after it is poured into the water.

First, let's find the number of moles of NaOH in 6.41 grams. We can use the formula:

moles (n) = mass (m) / molar mass (M)

The molar mass of NaOH can be calculated by adding the atomic masses of sodium (Na), oxygen (O), and hydrogen (H) from the periodic table.

Na: 22.99 g/mol
O: 16.00 g/mol
H: 1.01 g/mol

Molar mass of NaOH = 22.99 + 16.00 + 1.01 = 40.00 g/mol

moles of NaOH = 6.41 g / 40.00 g/mol = 0.16025 mol

Next, let's calculate the final volume of the solution. Since the volume of NaOH solution is given in mL and the volume of water is given in gallons, we need to convert the volume of water to mL.

1 gallon = 3.78541 liters
1 liter = 1000 mL

2.28 gallons = 2.28 * 3.78541 * 1000 mL = 8627.28 mL

Now we can calculate the concentration of NaOH in the final solution using the formula:

C1V1 = C2V2

Where:
C1 = initial concentration of NaOH solution = 0.250 M
V1 = initial volume of NaOH solution = 675 mL
C2 = final concentration of NaOH in the solution (what we need to find)
V2 = final volume of the solution (sum of initial volume of NaOH solution and volume of water) = 675 mL + 8627.28 mL = 9302.28 mL

Plugging in the values:

(0.250 M)(675 mL) = C2(9302.28 mL)

C2 = (0.250 M)(675 mL) / 9302.28 mL

C2 = 0.018 M

Therefore, the concentration of NaOH in the final solution is 0.018 M.

Convert 6.41g NaOH to moles. moles = grams/molar mass. Call this soln 1.

Convert the 0.25O M solution to moles. moles = M x L = ? Call this soln 2.

Convert 2.28 gallons H2O to L.

Add moles soln 1 to moles soln 2. Then total moles NaOH/L (from the 2.28 gallons) = M of the final soln with respect to NaOH.

Hint: Remember that reactions happen in

moles. So figure out the moles that reacted
then use the molarity formula to continue
solving the problem.
What volume of 0.699 M K3PO4 is required
to react with 68 mL of 0.661 MMgCl2 accord-
ing to the equation
2K3PO4 + 3MgCl2 ! Mg3(PO4)2 + 6KCl
Answer in units of mL