Thank you for answering the last question. Mass of Unknown B weighed for your po

Question

Thank you for answering the last question.

Mass of Unknown B weighed for your potentiometric titration: _______________ Molarity of your HCl (based on your standardization titrations): _____________ Volume of HCl needed to reach the bromocresol green endpoint for your potentiometric titration (The volume of HCl corresponding to the second spike on your first derivative graph.) ____________ Write the chemical equation for the reaction between HCl and Na_2CO_3 to completely protonate Na_2CO_3, and calculate the percent Na_2CO_3 in Unknown B. Show your work. Percent Na_2CO_3 in Unknown B ___________% Na_2CO_3

Explanation / Answer

Solution:- The balanced equation is..

Na2CO3 + 2HCl -----> 2NaCl + H2O + CO2

from this equation, Na2CO3 and HCl react in 1:2 mol ratio. we could calculate the moles of HCl from its given molarity and volume and then using the mol ratio we could calculate the moles of Na2CO3 that would be multiplied by molar mass to get its grams. molar mass of it is 106 g/mol.

39.925 ml x (1L/1000ml) x (0.09193 mol/L) x (1 mol Na2CO3/2mol HCl) x (106g Na2CO3/1mol Na2CO3)

= 0.1945 g Na2CO3

mass percent of Na2CO3 in unknown B = (0.1945/0.4415) x 100 = 44.05%

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