Question

determine the molarity of phosphoric acid if 20ml acid titrated with 15.9 ml of 0.200 m sodium hyhdroxide

Answer 1

To determine the molarity of phosphoric acid (H3PO4) when titrated with 15.9 mL of 0.200 M sodium hydroxide (NaOH), we can use the balanced equation and mole ratios. By calculating the moles of NaOH used and the resulting moles of H3PO4, we can determine the molarity of phosphoric acid.

Step-by-step explanation:

To determine the molarity of phosphoric acid, we can use the equation:

H3PO4 + 3 NaOH → Na3PO4 + 3 H2O

From the balanced equation, we can see that 1 mole of H3PO4 reacts with 3 moles of NaOH. Therefore, if 15.9 mL of 0.200 M NaOH is required to neutralize 20 mL of phosphoric acid, we can calculate the moles of NaOH used and the moles of H3PO4 present. Then, we can divide the moles of H3PO4 by the volume of the phosphoric acid to calculate the molarity.

Let's do the calculations:

1. Calculate the moles of NaOH: 15.9 mL * 0.200 mol/L = 3.18 mmol
2. Since the ratio between NaOH and H3PO4 is 3:1, there are also 3.18 mmol of H3PO4.
3. Calculate the molarity of H3PO4: Molarity = moles/volume = (3.18 mmol)/(20 mL) = 0.159 M

Answer 2

The molarity of phosphoric acid is 0.053 M.

Step-by-step explanation:

To determine the molarity of phosphoric acid, we need to use the equation of the balanced chemical reaction. Phosphoric acid (H3PO4) reacts with sodium hydroxide (NaOH) to form water (H2O) and sodium phosphate (Na3PO4).

The balanced equation is: H3PO4(aq) + 3NaOH(aq) → 3H2O(l) + Na3PO4(aq)

From the equation, we can see that the ratio of phosphoric acid to sodium hydroxide is 1:3. Since 15.9 mL of 0.200 M sodium hydroxide was used, the moles of sodium hydroxide can be calculated as follows: (15.9 mL)(0.200 mol/L) = 3.18 mmol NaOH.

Since the ratio of NaOH to H3PO4 is 3:1, the moles of phosphoric acid will be 1/3 of the moles of NaOH: (3.18 mmol NaOH)(1/3) = 1.06 mmol H3PO4.

Finally, to determine the molarity of phosphoric acid, divide the moles of H3PO4 by the volume of acid used in liters: (1.06 mmol H3PO4) / (20 mL) = 0.053 M H3PO4.