Family of Salts
Category : 10th Class
Washing Soda - \[N{{a}_{2}}C{{O}_{3}}.10{{H}_{2}}O\] (Sodium Carbonate Decahydrate)
It is manufactured by Solvay's process also known as ammonia soda process.
Raw Materials Required
Steps Involved
\[N{{H}_{3}}+{{H}_{2}}O+C{{O}_{2}}\to N{{H}_{4}}HC{{O}_{3}}\]
Ammonium hydrogen carbonate
\[N{{H}_{4}}HC{{O}_{3}}+NaCl\to N{{H}_{4}}Cl+NaHC{{O}_{3}}\]
\[2NaHC{{O}_{3}}\to N{{a}_{2}}C{{O}_{3}}+C{{O}_{2}}+{{H}_{2}}O\]
\[N{{a}_{2}}C{{O}_{3}}+10{{H}_{2}}O\to N{{a}_{2}}C{{O}_{3}}.10{{H}_{2}}O\]
(Washing soda)
Properties of Washing Soda
\[N{{a}_{2}}C{{O}_{3}}.10{{H}_{2}}O\to N{{a}_{2}}C{{O}_{3}}.{{H}_{2}}O+9{{H}_{2}}O\]
\[N{{a}_{2}}C{{O}_{3}}.10{{H}_{2}}O\to N{{a}_{2}}C{{O}_{3}}.{{H}_{2}}O\to N{{a}_{2}}C{{O}_{3}}\to C{{O}_{3}}(l)\]
\[N{{a}_{2}}C{{O}_{3}}+2HCl\to NaCl+{{H}_{2}}O+C{{O}_{2}}\]
Uses
Baking Soda (NaHCO3) (Sodium hydrogen carbonate)
\[N{{a}_{2}}C{{O}_{3}}+{{H}_{2}}O+C{{O}_{2}}\to 2NaHC{{O}_{3}}\] .
\[N{{H}_{3}}+{{H}_{2}}O+C{{O}_{2}}\to N{{H}_{4}}HC{{O}_{3}}\]
\[N{{H}_{4}}HC{{O}_{3}}+NaCl\to NaHC{{O}_{3}}+N{{H}_{4}}Cl\]
Properties of Sodium Hydrogen Carbonate
\[2NaHC{{O}_{3}}\to N{{a}_{2}}C{{O}_{3}}+C{{O}_{3}}+C{{O}_{2}}+{{H}_{2}}O\]
\[NaHC{{O}_{3}}+HCl\to NaCl+{{H}_{2}}O+C{{O}_{2}}\]
Uses
\[{{H}_{2}}S{{O}_{4}}+2NaHC{{O}_{3}}\to N{{a}_{2}}S{{O}_{4}}+2C{{O}_{2}}+2{{H}_{2}}O\]
Bleaching Powder \[(CaOC{{l}_{2}})\] (Calcium Oxychloride)
It is prepared by the action of chlorine gas on dry slaked lime.
\[Ca{{(OH)}_{2(S)}}+C{{l}_{2(g)}}\to CaC{{l}_{2(s)}}+{{H}_{2}}{{O}_{(l)}}\]
Because of this reaction bleaching powder is also called chloride of lime.
Properties
\[CaOC{{l}_{2}}+2HCl\to CaC{{l}_{2}}+C{{l}_{2}}+{{H}_{2}}O\]
\[CaOC{{l}_{2}}+{{H}_{2}}S{{O}_{4}}\to CaS{{O}_{4}}+{{H}_{2}}O+C{{l}_{2}}\]
Uses
Plaster of Paris \[(CaS{{O}_{4}}.\frac{1}{2}{{H}_{2}}O)\] (Calcium Sulphate Hemi hydrate)
It is prepared by heating gypsum at 390 k in a kiln.
\[2CaS{{O}_{4}}.2{{H}_{2}}{{O}_{(s)}}\to {{(CaS{{O}_{4}})}_{2}}{{H}_{2}}O+3{{H}_{2}}O\]
OR
\[CaS{{O}_{4}}.2{{H}_{2}}O\to CaS{{O}_{4}}.\frac{1}{2}{{H}_{2}}O+\frac{1}{2}{{H}_{2}}O\]
During manufacturing of plaster paris heating should be done carefully. Temperature should not exceed 390 k, else gypsum will loose all water molecule and anhydrous calcium sulphate will be formed.
Properties
\[CaS{{O}_{4}}\frac{1}{2}{{H}_{2}}O+\frac{1}{2}{{H}_{2}}O\to CaS{{O}_{4}}.2{{H}_{2}}O\]
For filling small gaps in walls and on roofs.
The water of crystallization of washing soda is:
(a) 10
(b) 9
(c) 5
(d) 1
(e) None of these
Answer: (a)
A salt on treatment with excess of ammonium hydroxide produces a complex tetraammine copper (II) ions. the salt contains:
(a) Cuprous ions
(b) Cupric ions
(c) Calcium ions
(d) Chloride ions
(e) None of these
Answer: (b)
Explanation
Cupric ions, as they react with excess of ammonia solution to form
\[{{[Cu{{(N{{H}_{3}})}_{4}}]}^{2+}}\]
When dilute hydrochloric acid is poured over powdered calcium carbonate, efflorescence are formed. It is because:
(a) Acids are corrosive
(b) Calicum carbonate is very reactive
(c) Calcium oxide in formed
(d) Carbon dioxide is evolved
(e) None of these
Answer: (d)
When sodium hydroxide is added to ammonium carbonate salt and then a glass rod dipped in dilute hydrochloric acid is brought near the test tube, we observe:
(a) Brisk efflorescence
(b) Dense white firms
(c) Yellowish green vapours
(d) Reddish brown gas
(e) None of these
Answer: (b)
A solution when reacts with zinc metal liberates a gas which burn with a pop sound. The pH of the solution is
(a) Equal to 7
(b) Less than 7
(c) Greaterthan7
(d) Between 8 and 14
(e) None of these
Answer: (b)
What is pH of a solution whose hydrogen ion concentration is \[1\times {{10}^{-3}}\] modes?
(a) 3
(b) 2
(c) 7
(d) 0-3
(e) None of these
Answer: (a)
Explanation
\[pH=-\log \,[{{H}^{+}}]\]
\[-\log \,[1\times {{10}^{-3}}]=-(-3)\log \,10=3\]
Aqueous solution of common salt is
(a) Acidic
(b) Alkaline
(c) Basic
(d) Neutral
(e) None of these
Answer: (d)
\[[{{H}^{+}}]=\] Concentration of hydrogen ion
\[{{H}_{3}}{{O}^{+}}=\] hydronium ion a = heat.
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