Laboratory Preparation of Nitric Acid
In the laboratory, nitric acid can be prepared by heating sodium or potassium nitrate with concentrated sulphuric acid to about 423-475 K.
NaNO3 + H2SO4 ——> NaHSO4 + HNO3
Anhydrous nitric acid can be obtained by distillation of concentrated aqueous nitric acid with P4010.
Manufacture of Nitric Acid
Nitric acid is commonly manufactured by Ostwald process in which it is prepared by the catalytic oxidation of ammonia by atmospheric oxygen. The reaction is carried out at about 500 K and 9 x 105 Pa (9 bar) pressure in the presence of Pt or Rh gauge as catalyst.
4NH3(g) + 502(g)——> 4NO(g) + 6H20(g) ΔH =- 90.2 kJ
Pt/Rh gauge, 500K, 9 bar
Nitric oxide thus formed combines with oxygen to form nitrogen dioxide.
2NO(g) + O2 (g) ——> 2 NO2 (g)
Nitrogen dioxide so formed, dissolves in water to give nitric acid.
3NO2 (g) + H2O(l) —–> 2HNO3(aq) + NO(g)
Dilute nitric acid is further concentrated by dehydration with concentrated sulphuric acid to get about 98% acid.
Properties of Nitric Acid
Physical Properties
<div class="code-block code-block-20" style="text-align:start; -webkit-text-stroke-width:0px; margin:8px 0px"> </div>
1) Pure nitric acid is a colourless liquid.
2) It has boiling point 355.6 K and freezing point 231.4 K.
3) laboratory grade nitric acid contains about 68% of HNO3 by mass and has a specific gravity of 1.504.
4) The impure acid is generally yellow due to the presence of nitrogen dioxide as impurity. Nitric acid containing dissolved nitrogen dioxide is known as fuming nitric acid.
5) It has a corrosive action on skin and produces painful blisters.
Chemical Properties
(1) Acidic character: It is one of the strongest acids because it is highly ionised in aqueous solution giving hydronium and nitrate ions.
2HNO3(aq) +H2O (l) ——> H3O+ + NO3¯(aq)
It turns blue litmus red. It forms salts with alkalies, carbonates and bicarbonates.
NaOH + HNO3 —-> NaNO3 + H2O
Na2CO3 + HNO3 —-> 2NaNO3 + H2O + CO2
NaHCO3 + HNO3 —-> NaNO3 + H2O + CO2
(2) Action on metals: With the exception of gold and platinum, nitric acid attacks all metals forming a variety of products. The product depends upon the nature of metal, the concentration of acid and temperature.
(A) Metals that are more electropositive than hydrogen (Mg, Al, Mn, Zn, Fe, Pb, etc.). In this case nascent hydrogen is liberated which further reduces nitric acid.
M + 2HNO3 ——> M(NO3)2 + 2H
HNO3 + H —-> Reduction product + H2O
The principal product is NO2, with conc. HNO3, N2O with dil. HNO3, and ammonium nitrate with very dil. HNO3.
For example: Zn reacts as:
Laboratory Preparation of Nitric Acid
In the laboratory, nitric acid can be prepared by heating sodium or potassium nitrate with concentrated sulphuric acid to about 423-475 K.
NaNO3 + H2SO4 ——> NaHSO4 + HNO3
Anhydrous nitric acid can be obtained by distillation of concentrated aqueous nitric acid with P4010.
Manufacture of Nitric Acid
Nitric acid is commonly manufactured by Ostwald process in which it is prepared by the catalytic oxidation of ammonia by atmospheric oxygen. The reaction is carried out at about 500 K and 9 x 105 Pa (9 bar) pressure in the presence of Pt or Rh gauge as catalyst.
4NH3(g) + 502(g)——> 4NO(g) + 6H20(g) ΔH =- 90.2 kJ
Pt/Rh gauge, 500K, 9 bar
Nitric oxide thus formed combines with oxygen to form nitrogen dioxide.
2NO(g) + O2 (g) ——> 2 NO2 (g)
Nitrogen dioxide so formed, dissolves in water to give nitric acid.
3NO2 (g) + H2O(l) —–> 2HNO3(aq) + NO(g)
Dilute nitric acid is further concentrated by dehydration with concentrated sulphuric acid to get about 98% acid.
Properties of Nitric Acid
Physical Properties
<div class="code-block code-block-20" style="text-align:start; -webkit-text-stroke-width:0px; margin:8px 0px"> </div>
1) Pure nitric acid is a colourless liquid.
2) It has boiling point 355.6 K and freezing point 231.4 K.
3) laboratory grade nitric acid contains about 68% of HNO3 by mass and has a specific gravity of 1.504.
4) The impure acid is generally yellow due to the presence of nitrogen dioxide as impurity. Nitric acid containing dissolved nitrogen dioxide is known as fuming nitric acid.
5) It has a corrosive action on skin and produces painful blisters.
Chemical Properties
(1) Acidic character: It is one of the strongest acids because it is highly ionised in aqueous solution giving hydronium and nitrate ions.
2HNO3(aq) +H2O (l) ——> H3O+ + NO3¯(aq)
It turns blue litmus red. It forms salts with alkalies, carbonates and bicarbonates.
NaOH + HNO3 —-> NaNO3 + H2O
Na2CO3 + HNO3 —-> 2NaNO3 + H2O + CO2
NaHCO3 + HNO3 —-> NaNO3 + H2O + CO2
(2) Action on metals: With the exception of gold and platinum, nitric acid attacks all metals forming a variety of products. The product depends upon the nature of metal, the concentration of acid and temperature.
(A) Metals that are more electropositive than hydrogen (Mg, Al, Mn, Zn, Fe, Pb, etc.). In this case nascent hydrogen is liberated which further reduces nitric acid.
M + 2HNO3 ——> M(NO3)2 + 2H
HNO3 + H —-> Reduction product + H2O
The principal product is NO2, with conc. HNO3, N2O with dil. HNO3, and ammonium nitrate with very dil. HNO3.
Uses of Nitric Acid
(i) It is used in the manufacture of ammonium nitrate for fertilizers.
(ii) It is used in the manufacture of sulphuric acid by lead chamber process.
(iii) It is used in the manufacture of explosives such as trinitro toluene (TNT), nitroglycerine, picric acid, etc.
(iv) It is used in the manufacture of dyes, perfumes and silk.
(v) It is used for the manufacture of nitrates for use in explosive and pyrotechnics.
(vi) It is used in picking of stainless steel and etching of metals.
(vii) It is also used as an oxidiser in rocket fuels.
(viii) It is used in the purification of gold and silver as aqua regia.
Gaurav Seth 4 years, 1 month ago
Laboratory Preparation of Nitric Acid
In the laboratory, nitric acid can be prepared by heating sodium or potassium nitrate with concentrated sulphuric acid to about 423-475 K.
NaNO3 + H2SO4 ——> NaHSO4 + HNO3
Anhydrous nitric acid can be obtained by distillation of concentrated aqueous nitric acid with P4010.
Manufacture of Nitric Acid
Nitric acid is commonly manufactured by Ostwald process in which it is prepared by the catalytic oxidation of ammonia by atmospheric oxygen. The reaction is carried out at about 500 K and 9 x 105 Pa (9 bar) pressure in the presence of Pt or Rh gauge as catalyst.
4NH3(g) + 502(g)——> 4NO(g) + 6H20(g) ΔH =- 90.2 kJ
Pt/Rh gauge, 500K, 9 bar
Nitric oxide thus formed combines with oxygen to form nitrogen dioxide.
2NO(g) + O2 (g) ——> 2 NO2 (g)
Nitrogen dioxide so formed, dissolves in water to give nitric acid.
3NO2 (g) + H2O(l) —–> 2HNO3(aq) + NO(g)
Dilute nitric acid is further concentrated by dehydration with concentrated sulphuric acid to get about 98% acid.
Properties of Nitric Acid
<div class="code-block code-block-20" style="text-align:start; -webkit-text-stroke-width:0px; margin:8px 0px"> </div>Physical Properties
1) Pure nitric acid is a colourless liquid.
2) It has boiling point 355.6 K and freezing point 231.4 K.
3) laboratory grade nitric acid contains about 68% of HNO3 by mass and has a specific gravity of 1.504.
4) The impure acid is generally yellow due to the presence of nitrogen dioxide as impurity. Nitric acid containing dissolved nitrogen dioxide is known as fuming nitric acid.
5) It has a corrosive action on skin and produces painful blisters.
Chemical Properties
(1) Acidic character: It is one of the strongest acids because it is highly ionised in aqueous solution giving hydronium and nitrate ions.
2HNO3(aq) +H2O (l) ——> H3O+ + NO3¯(aq)
It turns blue litmus red. It forms salts with alkalies, carbonates and bicarbonates.
NaOH + HNO3 —-> NaNO3 + H2O
Na2CO3 + HNO3 —-> 2NaNO3 + H2O + CO2
NaHCO3 + HNO3 —-> NaNO3 + H2O + CO2
(2) Action on metals: With the exception of gold and platinum, nitric acid attacks all metals forming a variety of products. The product depends upon the nature of metal, the concentration of acid and temperature.
(A) Metals that are more electropositive than hydrogen (Mg, Al, Mn, Zn, Fe, Pb, etc.). In this case nascent hydrogen is liberated which further reduces nitric acid.
M + 2HNO3 ——> M(NO3)2 + 2H
HNO3 + H —-> Reduction product + H2O
The principal product is NO2, with conc. HNO3, N2O with dil. HNO3, and ammonium nitrate with very dil. HNO3.
For example: Zn reacts as:
Laboratory Preparation of Nitric Acid
In the laboratory, nitric acid can be prepared by heating sodium or potassium nitrate with concentrated sulphuric acid to about 423-475 K.
NaNO3 + H2SO4 ——> NaHSO4 + HNO3
Anhydrous nitric acid can be obtained by distillation of concentrated aqueous nitric acid with P4010.
Manufacture of Nitric Acid
Nitric acid is commonly manufactured by Ostwald process in which it is prepared by the catalytic oxidation of ammonia by atmospheric oxygen. The reaction is carried out at about 500 K and 9 x 105 Pa (9 bar) pressure in the presence of Pt or Rh gauge as catalyst.
4NH3(g) + 502(g)——> 4NO(g) + 6H20(g) ΔH =- 90.2 kJ
Pt/Rh gauge, 500K, 9 bar
Nitric oxide thus formed combines with oxygen to form nitrogen dioxide.
2NO(g) + O2 (g) ——> 2 NO2 (g)
Nitrogen dioxide so formed, dissolves in water to give nitric acid.
3NO2 (g) + H2O(l) —–> 2HNO3(aq) + NO(g)
Dilute nitric acid is further concentrated by dehydration with concentrated sulphuric acid to get about 98% acid.
Properties of Nitric Acid
<div class="code-block code-block-20" style="text-align:start; -webkit-text-stroke-width:0px; margin:8px 0px"> </div>Physical Properties
1) Pure nitric acid is a colourless liquid.
2) It has boiling point 355.6 K and freezing point 231.4 K.
3) laboratory grade nitric acid contains about 68% of HNO3 by mass and has a specific gravity of 1.504.
4) The impure acid is generally yellow due to the presence of nitrogen dioxide as impurity. Nitric acid containing dissolved nitrogen dioxide is known as fuming nitric acid.
5) It has a corrosive action on skin and produces painful blisters.
Chemical Properties
(1) Acidic character: It is one of the strongest acids because it is highly ionised in aqueous solution giving hydronium and nitrate ions.
2HNO3(aq) +H2O (l) ——> H3O+ + NO3¯(aq)
It turns blue litmus red. It forms salts with alkalies, carbonates and bicarbonates.
NaOH + HNO3 —-> NaNO3 + H2O
Na2CO3 + HNO3 —-> 2NaNO3 + H2O + CO2
NaHCO3 + HNO3 —-> NaNO3 + H2O + CO2
(2) Action on metals: With the exception of gold and platinum, nitric acid attacks all metals forming a variety of products. The product depends upon the nature of metal, the concentration of acid and temperature.
(A) Metals that are more electropositive than hydrogen (Mg, Al, Mn, Zn, Fe, Pb, etc.). In this case nascent hydrogen is liberated which further reduces nitric acid.
M + 2HNO3 ——> M(NO3)2 + 2H
HNO3 + H —-> Reduction product + H2O
The principal product is NO2, with conc. HNO3, N2O with dil. HNO3, and ammonium nitrate with very dil. HNO3.
Uses of Nitric Acid
(i) It is used in the manufacture of ammonium nitrate for fertilizers.
(ii) It is used in the manufacture of sulphuric acid by lead chamber process.
(iii) It is used in the manufacture of explosives such as trinitro toluene (TNT), nitroglycerine, picric acid, etc.
(iv) It is used in the manufacture of dyes, perfumes and silk.
(v) It is used for the manufacture of nitrates for use in explosive and pyrotechnics.
(vi) It is used in picking of stainless steel and etching of metals.
(vii) It is also used as an oxidiser in rocket fuels.
(viii) It is used in the purification of gold and silver as aqua regia.
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