Pentaamminenitrocobalt

The orange-brown precipitate is collected by suction filtration on a 7-cm Buchner funnel, washed with 25 mL of ice water, and tested for the absence of any contaminating pentaamminenitrocobalt(III) chloride, which may be present in small amounts. Twenty-five milliliters of water is poured onto the precipitate and allowed to drain without suction into the filter flask, which has been emptied and rinsed with water. Suction is then applied, and 10 mL of 0.5 M ammonium oxalate is added to the yellowish-brown filtrate. No precipitate or only turbidity within 30 minutes indicates that the amount of pentaammine-... 

Given that the lattice energy of pentaamminenitrocobalt(III) chloride, [Co(NH3)5 (N02)]Cl2, is 1013 kJ/mol, estimate the effective ionic radius of the complex cation and speculate on the crystal structure of this compound rQy = 1.67 A). 

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