APPARATUS REQUIRED
i) crucible funnel
ii) Test tube is whatman filter paper
iii) Glass rod
iv) Beakers
v) Holders
CHEMICAL REQUIRED
i) Ferrous ammonium sulphate (0.8g)
ii) NH4Cl (5g)
iii) (1:1) ammonia solution
iv) (1:1) Concentrated HCL and HN03
THEORY:
Here, ferrous ion of Mohr's salt is oxidized to ferric state by conc. HNO3: Iron fromdemic salt Solution is precipitated as Fe(OH)3 by adding NH4OH in presence NH4Cl and the precipitate upon ignition gives Fe2O3 from the weight of Fe2O3 amount of Fe is Calculated.
Fe++ Conc. HNO3➡️ Fe+++
Fe+++)+3NH4OH•NH4CL➡️Fe(OH)3⬇️+3NH4
2Fe(OH)3 ➡️ Fe2O3 + 3H2O
Fe2O3 = Fe
159.689 Fe, Og contains 111-68g Fe+++
Fe(II) Bolt is oxidised with HND to Fe(lII) because Fe(ll) hydroxide is slightly soluble in water. Element like Al (IIl), Co (III), T; Zr which are pricipitated by ammonia soln must be absent Anions like arsenats, phosphate, vanadate silicate which yield insoluble compound of iron in ass medium must be absent. salts of hydroxy like citric, tartaric, salicylic and hydroxy compounds like glycerol, sugars, similarly alkali phosphate and fluoride must be absent, bec2 they form complex compound with Fe(III)
"The collodial particles are coagulated by raising tempr. hence, precipitation is carried out near boiling point. Fe(llI) hydroxide has tendency to absord other ions (e.g. +ve ion) present. It is minimized by the presence of excess NH4+ ( this volatilises during ignition).
The precipitation is alwas filtrated through filter paper because suction force the small particles of precipitate into pores of filtrer in media precipitate is wasted with NH4,NO3 Cvolatilises upon ignitation) Ammonia chloride is not used for washing,
Fe2O3 + 6NH4Cl ➡️ 2FeCl3 + 6NH3 + 3H₂O
Fe(lll)hydroxide of Ionic yields Fe2O3 At higher tempt. Fe3O4 is slowly formed. Fe2O3 may reduce thus ignition is carried out under good oxidising Condition
PROCEDURE
1) Accurate 0.8g ferrous ammonium sulphate weighted. Transferred it in a 500ml beaker provided. with stirrer and clock glass cover.
2) Added 1ml dil (1:1)HCL and 2ml conc. HNO3 and boiled gently (3 to 5 min) until colour was clear yellow
3) Dilute solution to 200ml heat to boiling and cool, added 5g of NH4Cl and added slowly with Stirring 1:1 ammonia solution waved air above Solution wth hand.
4) we kept on adding in slight excess until smell. ammonia was detected. Boiled liquid for 1min and allowed the precipitate to settle.
5) Decand the supernant liquid through quantitatives filter paper (whattman no.41)
6) washed precipitate by decandation 4 to 5 times using hot 1% ammonium nitrate Solution finally.transfer precipitate completely over filter paper
7) washed ppt again with ammonium nitrate Solution. free from cl- as dested with AgNo3
8) Dried the pricipitate in air oven and then ignite in previously weighted crucible
9) Headed the ppt in crucible crucible strongly for an hour with free acess of air.
10) Cooted the crucible in a desiccated and weighted it. finally calculated weight of iron in Fe2O3
OBSERVATION AND CALCULATION
weight of Mohr's salt (Fe(NH4)2•so4•6H2O] taken = 0.8g.
weight of ently crucible (w1) = 41.796g.
After ignition."
weight of crucible + Fe2O3 (w2) = 42.990 g.
weight of Fe2O3 = (w2 - w1)
= 42.990-41.796
= 1.194 g. (b)
obs. weight of Fe in Mohr's salt obtained as
Fe2O3 = 111.68 ÷ 159.68 x b g.
= 111.68 ÷ 159.68 × 1.94 g.
= 0.835/g. of Fe (c)
Theo. wt. of Fe in Mohr's salt
= 55.84 ÷ 392 ×a g.
= 55.84 ÷ 392 x 0.8 g.
= 0.114g of Fe(d)
Then,
experimental error:
= {d-c÷a}×100
= {0.114-0.835÷0.8}×100
= 92
RESULT
Hence, we observed 0.114g of Fe (theoritical wt) in a given sample.CONCLUSION
we can determine the amount of iron inMohr's salt as iron (III) oxide
 OXIDE){kind=link}
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