A 0.2861 gram sample of an unknown acid (HX) required 32.63 mL of 0.1045 M NaOH for neutralization to a phenolphthalein endpoint. What is the molar mass of the acid?
moles NaOH = M x L
Moles HX = same (the problem tells you it is HX; therefore, we know the reaction is 1:1 with NaOH).
moles HX = grams/molar mass.
You have moles and grams, solve for molar mass.
To determine the molar mass of the acid (HX), we can use the given information about its sample mass and the volume and the concentration of the NaOH solution used for neutralization.
First, let's calculate the number of moles of NaOH used:
moles of NaOH = volume of NaOH solution (L) × molarity of NaOH (mol/L)
Given that the volume of NaOH solution used is 32.63 mL (or 0.03263 L) and the molarity of NaOH is 0.1045 M, we can substitute these values into the equation:
moles of NaOH = 0.03263 L × 0.1045 mol/L
Now, let's determine the mole ratio between the acid (HX) and NaOH. From the balanced chemical equation, we know that for every 1 mole of acid (HX), 1 mole of NaOH is required for neutralization.
Therefore, the moles of acid (HX) will be equal to the moles of NaOH.
Next, we can use the equation for molar mass:
molar mass (g/mol) = mass of the sample (g) / moles of the substance (mol)
Substituting the values we have:
molar mass of the acid (HX) = mass of the sample (g) / moles of acid (HX)
Given that the mass of the sample is 0.2861 grams and we know the moles of acid (HX) is equal to the moles of NaOH, we can substitute these values into the equation:
molar mass of the acid (HX) = 0.2861 g / moles of NaOH
Now, we can calculate the molar mass of the acid (HX) using the information provided.