Explain with equation where appropriate, the functions of the following substances in the Solvay process: (i) limestone (ii) ammonia (iii) brine

 Explain with equation where appropriate, the functions of the following substances in the Solvay process: (i) limestone (ii) ammonia (iii) brine 

(b) Explain why the reaction between aqueous sodium trioxocarbonate (IV) solution and dilute hydrochloric acid is a neutralization reaction.

(c) Calculate the mass of sodium trioxocarbonate (IV) produced by the decomposition of 16.8g of sodium hydrogen trioxocarbonate (IV). (H=1, O=16, Na=23, S=33).

Solution:

(a)(i) Limestone is one of the principal raw materials which is heated to produce carbon (IV) oxide and quicklime which are important ingredients in the solvay process.

CaCO3(s) -h-e-a-t-> CaO(s) + CO2(g) 

(ii) Ammonia dissolves in concentrated sodium chloride solution (brine) to form ammoniacal brine which constitutes an important reactant in the Solvay process. Ammonia also reacts with CO2 to form NH4HCO3 (Ammonium hydrogen trioxocarbonate (IV)).

NH3(g) + CO2(g) + H2O(l) ---> NH4HCO3

(iii) Sodium chloride (brine) is a rich source of sodium which displaces ammonium ion from Ammonium Hydrogen trioxocarbonate (IV) (NaHCO3), is a major product of the Solvay process.

NH4HCO3(aq) + NaCl(aq) ---> NaHCO3(s) + NH4Cl(aq)

(b) When sodium trioxocarbonate (IV) is hydrolyzed in a chemical reaction with water, it produces a strong basic medium.

2Na+ CO32-  + 2H+2OH --->2NaOH + H2CO3.

Hence, the reaction between dilute hydrochloric and sodium trioxocarbonate (IV) solution can be said to be Acid-Base reaction, a neutralization reaction.

(c) There are two ways of answering this question.

Firstly Write out a balanced equation and calculate the molar mass of NaHCO3 and Na2CO3. 

2NaHCO3(s) -------> Na2CO3(s) + H2O(g) + CO2(g)

168g of NaHCO3 produced 106g of Na2CO3

16.8g of NaHCO3 will produce

106*16.8/168 = 10.6g of Na2CO3.

Secondly

Write a balanced equation of the reaction first. Calculate the molar mass of NaHCO3 and Na2CO3. 

2NaHCO3(s) ---> Na2CO3(s) + H20 + CO2(g)

mass                        mass

------                       -------

molar mass             molar mass

                                  

16.8g                      mass?

--------                  --------              CROSS MULTIPLY

168                         106

  

16.8*106=168*mass

mass= 16.8* 106/168=10.6g of Na2CO3

QUESTION SOURCE: WAEC 1988 THEORY QUESTION 11(a)(i)(ii)(iii)(b)(c)