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Difficulty: EasyIndustrial Chemical Processes and Biotechnology Applications

In the Solvay process for the industrial manufacture of sodium trioxocarbonate(IV), ammonia is an expensive reagent that must be recovered and reused to make the process economically viable. Which compound is reacted with ammonium chloride in the recovery tower to regenerate ammonia gas?

  1. Calcium hydroxideAnswer
  2. B
    Calcium chloride
  3. C
    Carbon(IV) oxide
  4. D
    Sodium chloride

Answer

Calcium hydroxide
Calcium hydroxide is a strong base that reacts with ammonium chloride in the Solvay process recovery plant according to the equation 2NH4Cl+Ca(OH)2→CaCl2+2H2O+2NH32NH_4Cl + Ca(OH)_2 \rightarrow CaCl_2 + 2H_2O + 2NH_3. This step regenerates ammonia gas for continuous recycling, making the Solvay process economically efficient.

Step-by-Step Solution

1
Identify the byproduct formed when ammonia reacts during the carbonating phase of the Solvay process.
Ammonium chloride (NH4ClNH_4Cl) is formed along with sodium hydrogentrioxocarbonate(IV) (NaHCO3NaHCO_3).
Ammonia absorbs carbon(IV) oxide and reacts with brine to form ammonium chloride in solution.
2
Determine the reagent added to ammonium chloride in the recovery tower to liberate free ammonia gas.
Calcium hydroxide (Ca(OH)2Ca(OH)_2), obtained from slaking quicklime (CaOCaO), is added.
Ammonium salts react with strong bases like calcium hydroxide upon heating to yield ammonia gas, water, and a calcium salt.
3
Write the balanced chemical equation for the recovery step.
2NH4Cl(aq)+Ca(OH)2(aq)→CaCl2(aq)+2H2O(l)+2NH3(g)2NH_4Cl(aq) + Ca(OH)_2(aq) \rightarrow CaCl_2(aq) + 2H_2O(l) + 2NH_3(g)
This reaction regenerates ammonia gas, which is recycled back into the ammoniating tower.

Key Concept

Ammonia recovery in the industrial Solvay process using calcium hydroxide
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Topics

Industrial Chemical Processes and Biotechnology Applications