The source of Fe^3+ is the commercially available solid reagent, iron (III) nitr

Question

The source of Fe^3+ is the commercially available solid reagent, iron (III) nitrate nonahydrate, whose formula is Fe(NO_3)_3 middot 9 H_2O. When computing the molecular weight of this reagent, be sure to include the nine water molecules in the formula above. All solutions containing Fe^3+ should be prepared in 0.5 M nitric acid and not in distilled water. This is because Fe^3+ forms polymeric iron hydroxy species at neutral or basic pH that will interfere with the analysis method - at acidic pH formation of these species is suppressed. If any of your Fe^3+ solutions are distinctly orange or yellow without addition of any SCN^-, this means you neglected to prepare the solutions in 0.5 M nitric acid, and these solutions must then be discarded and prepared again. The source for SCN^- is another commercially available solid, KSCN. SCN^- slow decomposes in 0.5 M HNO_3, so all solutions containing only SCN^- should be prepared water. Furthermore, Fe(SCN)^2+ solutions cannot be stored due to the SCN these must be discarded at the end of the laboratory period.

Explanation / Answer

Fe(NO3)3. 9H2O

In order to determine molecular weight of ferric nitrate , the nine water of crystallization present in the molecule need to included in molecular wieght.

molecular weight = (1* atomic mass of Fe) + (3* atomic mass of N) + (9 * Atomic mass of O) + 9 * [(2 * atomic mass of H) + (1 * atomic mass of oxygen)]

Molecular wieght = (1* 56) + (3 *14) + (9 * 16) + 9 [(2 * 1) + (1 * 16)]

= 404 g/mol

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