a 10.0mL sample of an unknown H3PO4 solution requirs 112mL of 0.100 M KOH to completely react with the H3PO4. What was the concentrartion of the unknown H3PO4 solution?

H3PO4 + 3KOH -----> 3H2O + K3PO4
Ive seen these problems with one volume but not two volumes Im lost please help me with this problem

DrBob222 I think Im doing something wrong. When I worked this problem out I came up with the right answer but wrong units.

0.112L KOH x 0.100molKOH/LKOH x 1mol H3PO4/3 mol KOH x 0.01 L H3PO4/1 mol H3PO4 = 0.373 L H3PO4

To solve this problem, we can use the concept of stoichiometry. Here's how you can calculate the concentration of the unknown H3PO4 solution:

1. Write the balanced chemical equation:

H3PO4 + 3KOH → 3H2O + K3PO4

2. Determine the molar ratio between H3PO4 and KOH from the balanced equation:

From the balanced equation, we can see that the ratio is 1 mole of H3PO4 reacts with 3 moles of KOH.

3. Calculate the number of moles of KOH used in the reaction:

Given that the volume of KOH used is 112 mL, which is 0.112 L (convert mL to L), and the concentration of KOH is 0.100 M, we can use the formula:

moles of KOH = concentration × volume
moles of KOH = 0.100 M × 0.112 L = 0.0112 mol

4. Use the molar ratio from step 2 to determine the number of moles of H3PO4:

Since the ratio of KOH to H3PO4 is 3:1, the number of moles of H3PO4 used is 0.0112 mol ÷ 3 = 0.00373 mol.

5. Calculate the concentration of H3PO4 in the unknown solution:

The sample volume provided is 10.0 mL, which is 0.010 L (convert mL to L). To find the concentration (M) of H3PO4, use the formula:

concentration of H3PO4 = moles of H3PO4 ÷ volume
concentration of H3PO4 = 0.00373 mol ÷ 0.010 L = 0.373 M

Therefore, the concentration of the unknown H3PO4 solution is 0.373 M.

To solve this problem, we can first determine the moles of KOH used in the reaction, and then use that information to calculate the concentration of the unknown H3PO4 solution.

1. Calculate the moles of KOH used:
The given volume of KOH solution is 112 mL, and its concentration is 0.100 M (moles per liter). To convert the volume to liters, divide by 1000:
112 mL ÷ 1000 = 0.112 L
Now, use the equation:
Moles of KOH = volume (L) × concentration (M)
Moles of KOH = 0.112 L × 0.100 M = 0.0112 moles

2. Determine the mole ratio between KOH and H3PO4:
From the balanced chemical equation:
H3PO4 + 3KOH → 3H2O + K3PO4
We see that 1 mole of H3PO4 reacts with 3 moles of KOH.

3. Calculate the moles of H3PO4 in the unknown solution:
Since the mole ratio between H3PO4 and KOH is 1:3, the moles of H3PO4 in the unknown solution are:
Moles of H3PO4 = 0.0112 moles × (1 mole H3PO4 / 3 moles KOH) = 0.00373 moles

4. Calculate the concentration of the unknown H3PO4 solution:
The given volume of the unknown H3PO4 solution is 10.0 mL, which is equal to 0.0100 L (10.0 mL ÷ 1000).
Concentration (M) = Moles / Volume (L)
Concentration of H3PO4 = 0.00373 moles / 0.0100 L = 0.373 M

Therefore, the concentration of the unknown H3PO4 solution is 0.373 M.

That's not a big complication.

moles KOH = M x L = ?
Convert moles KOH to moles H3PO4 with the coefficients in the balanced equation.
M H3PO4 = moles H3PO4/L H3PO4.
done.