Unit: Stoichiometry Lesson: #10 Topics: Solvay Process

Unit: Stoichiometry Lesson: #10 Topics: Solvay Process The Solvay Process: A Case Study  Many important industrial processes involve chemical reactions that are difficult to perform and still be economically feasible.  In some cases, the overall process must follow a series of reaction steps.  Sodium carbonate is a chemical that is needed in large amounts – it is used in the production of glass and soap.  Historically, sodium carbonate was produced by burning plants or coal and mixing the ashes with water  This method was both inefficient and very expensive because of the large amount of material that needed to be burned.  The Solvay process was developed as a cost effective alternative. It involves a series of reaction steps and has a net reaction of: CaCO3 (s) + 2 NaCl (aq)  Na2CO3 (aq) + CaCl2 (aq)  A net reaction is determined by looking at the various reaction steps and eliminating any chemical that appears as both a reactant and a product in the various steps. These chemicals are known as intermediates.  Step 1: Calcium carbonate (limestone) is decomposed by heat to form calcium oxide (lime) and carbon dioxide. CaCO3 (s)  CaO (s) + CO2 (g)  Step 2: Carbon dioxide reacts with aqueous ammonia and water to form aqueous ammonium hydrogen carbonate. CO2 (g) + NH3 (aq) + H2O (l)  NH4HCO3 (aq)  Step 3: The aqueous ammonium hydrogen carbonate reacts with sodium chloride to produce ammonium chloride and solid baking soda. NH4HCO3 (aq) + NaCl (aq)  NH4Cl (aq) + NaHCO3 (s)  Step 4: The baking soda is heated up and decomposed into sodium carbonate, water vapor and carbon dioxide. 2 NaHCO3 (s)  Na2CO3 (s) + H2O (g) + CO2 (g)  Step 5: The lime that was produced in the first step is mixed with water to produce slaked lime (calcium hydroxide). CaO (s) + H2O (l)  Ca(OH)2 (s)  Step 6: The slaked lime is added to the ammonium chloride produced in the third step to produce ammonia, calcium chloride and water. Ca(OH)2 (s) + 2 NH4Cl (aq)  2 NH3 (aq) + CaCl2 (aq) + 2 H2O (l)  Net Reaction): CaCO3 (s) + 2 NaCl (aq)  Na2CO3 (s) + CaCl2 (aq)  The two raw materials used up in the Solvay process (calcium carbonate and sodium chloride) are abundantly available and very cheap.  The primary product is the sodium carbonate.  A by-product is the calcium chloride which can be sold as a dessicant or as road salt to melt ice.  The baking soda made in step 3 can also be sold as a byproduct but this limits the amount of sodium carbonate that can be produced. Homework:  See accompanying sheet. <ul style="display: flex;"><li style="flex:1">Chem 20 </li><li style="flex:1">Stoichiometry and the Solvay Process </li></ul>Use a above balanced equation to answer each of the following questions. 1. What mass of lime (see step 1 for names) can be produced by the decomposition of 400 kg of limestone in step 1 of the Solvay process? m = 224 kg 2. What volume of 1.45 mol/L ammonia would be required to produce 275 kg of ammonium hydrogen carbonate in step 2 of the Solvay process? V = 2.40 X 103 L 3. What volume of 0.75 mol/L sodium chloride would be required to react with 350 kg of ammonium hydrogen carbonate in step 3 of the Solvay process? V = 5.9 X 103 L 4. What volume of carbon dioxide gas will be generated at SATP by the decomposition of 180 kg of sodium hydrogen carbonate in step 4 of the Solvay process? V = 2.66 X 104 L 5. What mass of water is required to react with lime in step 5 of the Solvay process in order to produce 370 kg of slaked lime? m = 90.0 kg 6. Calculate the concentration of ammonium chloride if 87 kL is required to react with 190 kg of slaked lime in step 6 of the Solvay process. C = 0.059 mol/L 7. What mass of sodium carbonate can be produced during the Solvay process if 250 kg of calcium carbonate is allowed to react with 3000 L of 1.72 mol/L sodium chloride (refer to the net reaction equation)? m = 265 kg

Unit: Stoichiometry Lesson: #10 Topics: Solvay Process

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