Neutralization Titrations: The Determination of Soda Ash

Neutralization Titrations: The Determination of Sodium Carbonate from Unknown Soda Ash
Unknown #
I. Purpose: The goal of this experiment is to determine the weight % of Na2CO3 through the preparation of NaOH and HCl standards. The molarity of the standards will be found through titration of KHP for NaOH, HCl vs the known NaOH, and the unknown Soda Ash sample vs the known HCl.

II. Equations and Sample Calculations:

Titration of HCl with NaOH:
Complete Equation:
HCl (aq) + NaOH (aq)  H2O (l) + NaCl (aq)

Net Ionic Equation:
H+ + OH-  H2O(l)

Calculations (10mL 0.1M HCL, 100mL H20, 7.8mL NaOH):

# mols NaOH = 0.1M (known concentration) x 0.0078L (titrated volume) = 0.00078mol

1:1 ratio mol NaOH to HCL = 0.00078 mol HCl

M HCl= = 0.078 M HCl

Standardization of NaOH vs KHP
Complete Equation:
NaOH + KHC8H4O4  KNaC8H4O4 + H2O

Net Ionic Equation:
OH- + HC8H4O4-  C8H4O42- + H20

Calculations (0.3291g KHP, 18mL NaOH):

# mols/M NaOH: = = 0.089M NaOH

Determination of the Unknown Soda Ash Sample (Unknown # 67):
Complete Equation:
Na2CO3 (aq) + 2HCl  CO2 (g) + H2O (l) + 2NaCl (aq)

Net Ionic Equation:
CO32- + 2H+  H2O + CO2

Calculations (0.1887g Soda Ash, reaction completed with 22.80mL HCL total):

#mols HCL = 0.0228L x 0.078M (standardized HCL M) = 0.00117mol
#moles Na2CO3 = 2:1 HCl : Na2CO3  = = 0.00089 mol
Grams Na2CO3 = 0.00089mol x 106.0 g/mol = 0.094g

% Na2CO3 by wt = X 100 = 49.94%
III. Data and Results
All titrations done with micropipette #8. All masses found using balance #16.

Standardization of HCl with NaOH
10mL 0.1M HCl diluted in 100mL H2O, Titrated with NaOH

Volume NaOH (mL) Description of Color at volume added
Flask #1 7.8 Dark pink, fast change
Flask #2 7.85 Light pink, fast change
Flask #3 7.9 Light pink, slow change

Mean Volume NaOH: 7.85 mL
SD: 0.05
RSD: 0.64%
Standardization of 0.1M NaOH
Quantity of KHP added to 100mL H20, Phenolphthalein indicator then titrated