It is found that 24.68 mL of 0.1165 NaOH is needed to titrate 0.2931 g of an unknown acid to the phenolphthalein end point. What is the equivalent mass of the acid?

equivalent mass = grams acid/moles H+

1-10 complete the (%m)of 54.00g of AgNo3 is dissolved in 128.00g of weter

To find the equivalent mass of the acid, we need to determine the moles of H+ ions in the reaction. Since NaOH is a strong base, it can be assumed that it fully dissociates in water, producing one mole of OH- ions for every mole of NaOH.

First, we need to find the moles of NaOH used in the reaction. To do this, we'll use the molarity (concentration) of NaOH and the volume used.

moles of NaOH = molarity × volume (in liters)
moles of NaOH = 0.1165 mol/L × (24.68 mL / 1000 mL/L)
moles of NaOH = 0.1165 mol/L × 0.02468 L
moles of NaOH = 0.00287762 mol

Since the reaction between NaOH and the acid is a 1:1 ratio, the moles of NaOH are equal to the moles of H+ ions produced by the acid.

Next, we need to find the mass of the acid used in the reaction. We are given that the mass of the acid is 0.2931 g.

Finally, we can calculate the equivalent mass of the acid using the formula:

equivalent mass = grams acid / moles H+

equivalent mass = 0.2931 g / 0.00287762 mol
equivalent mass ≈ 101.808 g/mol

Therefore, the equivalent mass of the acid is approximately 101.808 g/mol.