SODA ASH
Experiment
ANALYSIS OF SODA ASH
The CCLI Initiative
Computers in Chemistry Laboratory Instruction
LEARNING OBJECTIVES
The objectives of this experiment are to . . .
•
understand the titration curve for a diprotic base.
•
use the titration curve to calculate the percent of Na2 CO3 in an unknown sample of soda ash.
BACKGROUND
Sodium carbonate is an important industrial chemical. It is used in the manufacture of soap, glass, paper and as a source of alkalinity, that is, as a base. About half the sodium carbonate used in the United States is manufactured by the Solvay process. In this process, which is carried out at 0 °C, carbon dioxide is bubbled through a concentrated sodium chloride solution which is saturated with ammonia. Sodium hydrogen carbonate precipitates from the solution and is isolated:
CO2(g) + NH3(g) + H2O(l) + Na+ (aq) + Cl! (aq) ==> NaHCO3(s) + NH4+ (aq) Cl! (aq)
(1)
When heated to 300 °C, the sodium hydrogen carbonate decomposes to form sodium carbonate, carbon dioxide, and water.
2 NaHCO3(s) ==> Na2 CO3(s) + CO2(g) + H2 O(g)
(2)
The crude product obtained from this thermal decomposition is called soda ash, which is primarily Na2 CO3 , although it also contains unreacted NaHCO3 and other impurities.
The total acid neutralizing capacity of a soda ash sample, its alkalinity value, can be stated in terms of percent sodium carbonate. In doing so, any sodium hydrogen carbonate present in the sample is converted to its equivalent neutralizing capacity in terms of sodium carbonate. That is, a 100% NaHCO3 sample is represented as a 50% Na2 CO3 sample in terms of its acid neutralization capacity. It is sometimes convenient for chemical purposes to group compounds of similar behavior together and then state composition in terms of only one of them. For example, the potassium content of fertilizer is stated as percent K2 O, although the potassium compounds actually present may be phosphates, nitrates or
ANALYSIS OF SODA ASH
The CCLI Initiative
Computers in Chemistry Laboratory Instruction
LEARNING OBJECTIVES
The objectives of this experiment are to . . .
•
understand the titration curve for a diprotic base.
•
use the titration curve to calculate the percent of Na2 CO3 in an unknown sample of soda ash.
BACKGROUND
Sodium carbonate is an important industrial chemical. It is used in the manufacture of soap, glass, paper and as a source of alkalinity, that is, as a base. About half the sodium carbonate used in the United States is manufactured by the Solvay process. In this process, which is carried out at 0 °C, carbon dioxide is bubbled through a concentrated sodium chloride solution which is saturated with ammonia. Sodium hydrogen carbonate precipitates from the solution and is isolated:
CO2(g) + NH3(g) + H2O(l) + Na+ (aq) + Cl! (aq) ==> NaHCO3(s) + NH4+ (aq) Cl! (aq)
(1)
When heated to 300 °C, the sodium hydrogen carbonate decomposes to form sodium carbonate, carbon dioxide, and water.
2 NaHCO3(s) ==> Na2 CO3(s) + CO2(g) + H2 O(g)
(2)
The crude product obtained from this thermal decomposition is called soda ash, which is primarily Na2 CO3 , although it also contains unreacted NaHCO3 and other impurities.
The total acid neutralizing capacity of a soda ash sample, its alkalinity value, can be stated in terms of percent sodium carbonate. In doing so, any sodium hydrogen carbonate present in the sample is converted to its equivalent neutralizing capacity in terms of sodium carbonate. That is, a 100% NaHCO3 sample is represented as a 50% Na2 CO3 sample in terms of its acid neutralization capacity. It is sometimes convenient for chemical purposes to group compounds of similar behavior together and then state composition in terms of only one of them. For example, the potassium content of fertilizer is stated as percent K2 O, although the potassium compounds actually present may be phosphates, nitrates or