An impure sample of (COOH)2 ·2 H2O that

has a mass of 3.4 g was dissolved in water
and titrated with standard NaOH solution.
The titration required 42.7 mL of 0.156 molar
NaOH solution. Calculate the percent
(COOH)2 · 2 H2O in the sample.
Answer in units of %.

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(COOH)2.2H2O + 2NaOH ==> (COONa)2 + 4H2O

mols NaOH = M x L = ?
mols (COOH)2 = 2 x mols NaOH from the coefficients in the balanced equation.
grams (COOH)2.2H2O = mols x molar mass. This is the theoretical yield (TY)
%(COOH)2.2H2O in the sample is
(TY/mass sample)*100 = ?

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To calculate the percent (COOH)2 · 2 H2O in the sample, we need to determine the moles of (COOH)2 · 2 H2O and the total mass of the impure sample.

Let's break down the steps to solve the problem:

Step 1: Calculate the moles of NaOH used in the titration.
The volume of NaOH solution used is given as 42.7 mL. We need to convert this to liters:
42.7 mL = 42.7 / 1000 = 0.0427 L

The molarity of the NaOH solution is given as 0.156 mol/L.
Using the formula: moles = molarity × volume, we can calculate the moles of NaOH:
moles of NaOH = 0.156 mol/L × 0.0427 L

Step 2: Calculate the moles of (COOH)2 · 2 H2O.
According to the balanced chemical equation, the reaction between NaOH and (COOH)2 · 2 H2O has a 1:1 stoichiometric ratio. This means that the moles of NaOH used in the titration are equal to the moles of (COOH)2 · 2 H2O in the sample.

Step 3: Calculate the moles of (COOH)2 · 2 H2O in the sample.
We know the moles of NaOH from Step 1. Let's use that value to calculate the moles of (COOH)2 · 2 H2O:
moles of (COOH)2 · 2 H2O = moles of NaOH

Step 4: Calculate the mass of (COOH)2 · 2 H2O in the sample.
The mass of the sample is given as 3.4 g.

Step 5: Calculate the percent (COOH)2 · 2 H2O in the sample.
The percent (COOH)2 · 2 H2O in the sample can be calculated using the formula:
% (COOH)2 · 2 H2O = (moles of (COOH)2 · 2 H2O / mass of sample) × 100

Let's plug in the values into the formula:

% (COOH)2 · 2 H2O = (moles of NaOH / mass of sample) × 100

Now you need to calculate the values for moles of NaOH and mass of the sample, and then substitute these values into the formula to solve for the percent (COOH)2 · 2 H2O.