an impure sample of oxalic acid C2O4H2, with a mass of 0.465g, is dissolved in water. a few drops of phenolphthalein indicator solution are added, and the solution is titrated with 0.190 mol/L aqueous sodium hydroxide held in a burette. the solutointurns pink when 49.5mL of sodium hydroxide has been added. what is the percent purity of the oxalic acid sample.
please somebody help me with that is a assignment and i need to finish it and also understand it clearly....so plz can someone show me how to do it with steps and tell me the answer too plzzzzzzzzz......thank you :)
H2C2O4 + 2NaOH ==> Na2C2O4 + 2H2O
moles NaOH = M x L = ??
moles H2C2O4 = 2 times moles NaOH (from the equation).
grams H2C2O4 = moles H2C2O4 x molar mass H2C2O4.
%H2C2O4 in sample = (grams H2C2O4/mass sample)*100 = ??
To determine the percent purity of the oxalic acid sample, you need to understand the concept of titration and use stoichiometry to calculate the amount of oxalic acid present in the impure sample.
Here are the steps to solve the problem:
Step 1: Calculate the number of moles of sodium hydroxide used.
To do this, you can use the formula:
Number of moles = concentration (mol/L) × volume (L)
Given the concentration of sodium hydroxide as 0.190 mol/L and the volume used as 49.5 mL (which is equal to 0.0495 L), you can calculate the number of moles of sodium hydroxide used as follows:
Number of moles = 0.190 mol/L × 0.0495 L = 0.0093975 mol
Step 2: Determine the balanced chemical equation for the reaction between oxalic acid (C2O4H2) and sodium hydroxide (NaOH).
The balanced chemical equation is:
C2O4H2 + 2 NaOH → 2 H2O + Na2C2O4
From the balanced equation, you can see that 1 mole of oxalic acid reacts with 2 moles of sodium hydroxide.
Step 3: Use stoichiometry to calculate the number of moles of oxalic acid in the impure sample.
Since 2 moles of sodium hydroxide react with 1 mole of oxalic acid, you can calculate the number of moles of oxalic acid as follows:
Number of moles of oxalic acid = (0.0093975 mol NaOH) / 2 = 0.00469875 mol
Step 4: Calculate the mass of the impure sample of oxalic acid.
To do this, you can use the formula:
Mass = Number of moles × molar mass
The molar mass of oxalic acid (C2O4H2) can be calculated as follows:
Molar mass = 2 × (C atomic mass) + 4 × (O atomic mass) + 2 × (H atomic mass)
= 2 × (12.01 g/mol) + 4 × (16.00 g/mol) + 2 × (1.008 g/mol)
= 126.07 g/mol
Now, you can calculate the mass of the impure sample of oxalic acid as follows:
Mass = 0.00469875 mol × 126.07 g/mol = 0.5900 g
Step 5: Calculate the percent purity of the oxalic acid sample.
The percent purity can be calculated using the formula:
Percent purity = (pure mass / impure mass) × 100%
Given that the pure mass of oxalic acid is 0.465 g (as stated in the problem), you can calculate the percent purity as follows:
Percent purity = (0.465 g / 0.5900 g) × 100% ≈ 78.98%
Therefore, the percent purity of the oxalic acid sample is approximately 78.98%.