How many mL of 0.0500 M phosphoric acid (H3PO4) are needed to titrate completely 50.0 mL of 0.150 M barium hydroxide (Ba(OH)2)) solution?

1. Write the equation and balance it.

2. moles Ba(OH)2 = M x L
3. Using the coefficients in the balanced equation, convert moles Ba(OH)2 to moles H3PO4.
4. M = moles/L. Substitute M and moles H3PO4 and solve for L.

The answer is 50.0 mL

To determine the volume of phosphoric acid needed to titrate the barium hydroxide solution completely, we can use the concept of stoichiometry. Here's how you can calculate it:

Step 1: Write and balance the equation for the reaction between phosphoric acid and barium hydroxide:

H3PO4 + 3Ba(OH)2 --> Ba3(PO4)2 + 6H2O

According to the balanced equation, one mole of phosphoric acid (H3PO4) reacts with 3 moles of barium hydroxide (Ba(OH)2).

Step 2: Determine the number of moles of barium hydroxide used in the titration:

Given that the volume of the barium hydroxide solution is 50.0 mL and the concentration is 0.150 M, we can use the formula:

moles = concentration × volume
moles of Ba(OH)2 = 0.150 M × 0.0500 L (converting mL to L)
moles of Ba(OH)2 = 0.00750 mol

Step 3: Determine the number of moles of phosphoric acid required:

According to the stoichiometry of the balanced equation in step 1, it takes 1 mole of H3PO4 to react with 3 moles of Ba(OH)2. Therefore, the moles of H3PO4 required can be calculated as:

moles of H3PO4 = (moles of Ba(OH)2 / 3)
moles of H3PO4 = (0.00750 mol / 3)
moles of H3PO4 = 0.00250 mol

Step 4: Calculate the volume of phosphoric acid needed:

Given the concentration of phosphoric acid (H3PO4) is 0.0500 M, we can use the formula:

volume = moles / concentration
volume = 0.00250 mol / 0.0500 M
volume = 0.0500 L (converting from L to mL)

Therefore, you would need 50.0 mL of 0.0500 M phosphoric acid to titrate completely with 50.0 mL of 0.150 M barium hydroxide solution.