Final answer:
To calculate the percentage purity, we first determine the moles of HCl reacting with sodium carbonate, then use the mole ratio to find the pure sodium carbonate's moles, and from there, find the mass and compare it to the initial impure mass. The result is a 38.16% purity and consequently 61.84% impurity of the sodium carbonate base.
Step-by-step explanation:
Calculating Percentage Purity and Impurity of a Base
The question involves a titration process where a known volume of HCl is required to neutralize a sodium carbonate solution. To calculate the percentage purity of the base, we need to determine the mass of pure sodium carbonate that reacted with HCl.
First, we calculate the number of moles of HCl used. With the molar ratio between HCl and sodium carbonate, we can then find the moles of pure sodium carbonate. Knowing the molar mass of sodium carbonate, we calculate the mass of the pure substance that would have been in our solution if it were 100% pure. Finally, we compare this calculated mass with the initial mass given.
The steps to find the percentage purity of the sodium carbonate base are:
- Calculate the number of moles of HCl:
(18.00 cm³ HCl) x (1 dm³ / 1000 cm³) x (1 mole HCl / 1 dm³) = 0.018 moles HCl. - Calculate the number of moles of sodium carbonate using the stoichiometry of the reaction, which is a 1:1 ratio with HCl: 0.018 moles sodium carbonate.
- Calculate the mass of pure sodium carbonate:
(0.018 moles) x (105.99 g/mole) = 1.90782 g of pure sodium carbonate. - Calculate the percentage purity:
(1.90782 g / 5.00 g) x 100 = 38.16% purity.
To find the percentage impurity, simply subtract the percentage purity from 100%:
100% - 38.16% = 61.84% impurity.