Answer:
101.8 g/ equiv
Explanation:
The equivalence point for a titration is reached when
# Equivalents of Acid = # Equivalents of Base
and the number of equivalents is defined as the mass divided into the equivalent weight.
The equivalent weight is the molecular weight divided into the number of protons ( H⁺) per formula of the acid and number of hydroxyl groups ( OH⁻ ) for the base.
Now we are not told in this question the number of protons, H⁺, so lets assume our unknown is monoprotic acid.
From the formulas above we can set the following expression
#~Equiv Acid = mass/ equiv Weight = # Equiv NaOH = V NaOH x Equiv Wt
Since we used 24.68 mL of .1165 M of NaOH for the titration the equivalents are:
= ( 24.68 mL x 1 L /1000 mL ) x 0.1165 mol / L NaOH
= 0.0029 mol = 0.00288 equiv ( 1 OH⁻ )
and,
Equiv acid = 0.0029 equiv
Equiv acid = 0.2931 / Equiv Weight
Equiv Weight = 0.2931 q / 0.00288 equiv
⇒ Equiv Weight = 101.8 g/ equiv
The equivalent mass of the acid should be 101.94 g/mol.
But first determine the moles of NaOH
Moles = molarity(M) * Volume(L)
= 0.1165M * 0.02468L
= 0.00287522mol
Now
moles = mass / molar mass
molar mass = 0.2931g / 0.002875mol
= 101.94 g/mol
This value should be the equivalent mass of the unknown acid.
hence, The equivalent mass of the acid should be 101.94 g/mol.
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