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Topic: Word Problem concerning Q's on: % mass and gravimetric factor  (Read 9551 times)

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Offline Funk Master Widge

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Word Problem concerning Q's on: % mass and gravimetric factor
« on: September 03, 2008, 06:57:15 PM »
A nickel (II) ammonia compound was prepared in the laboratory.  Its formula was supposed to be [Ni(NH3)6](NO3)2.  In order to verify the composition of the compound, a solution of the compound was treated with the reagent  dimethylglyoxime.  This reagent reacts with nickel (II) to produce an insoluble red compound Ni(DMG)2.
0.1324 gram of the nickel ammonia compound was dissolved in water and treated with an excess of the dimethylglyoxime reagent.  The mass of the red Ni(DMG)2] produced was 0.1343 gram.

Molar masses:
[Ni(NH3)6](NO3)2 = 284.887 g/mol
Ni(DMG)2 = 288.917 g/mol
Ni = 58.693 g/mol

1.) Calculate the mass of nickel in the nickel(II) ammonia compound.

2.) Calculate the %mass of nickel in the compound.

3.) What percent mass of nickel was expected?

4.) What is the gravimetric factor for this analysis?

1 - I think that the mass of nickel would be the mass for 1 molar mass, 58.69g Ni.

2 - And I think that the %mass of nickel is 20.60%, but I'm not sure.

3 - The %mass nickel that is expected is the theoretical yield.  So would you find the % mass Nickel of Ni(DMG)2 ?
Otherwise i dont understand why the masses are given if theyre not used, but they probably are to be used and i just dont know how so..

4 - Gravimetric factor isnt in wikipedia but it means something along the lines of gravitational force of the ions.  Our teacher in GT last year didnt show us that so i dont know what it is or the units.

Offline Borek

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Re: Word Problem concerning Q's on: % mass and gravimetric factor
« Reply #1 on: September 04, 2008, 03:04:12 AM »
Gravimetric factor is a ratio of the mass of a determined substance to the mass of compound made during weight analysis.

For example, if you plan to determine calcium in water, and you precipitate it as CaCO3, gravimetric factor for this analysis will MCa/MCaCO3 = 40.08/100.09 (where M is a molar mass).

If you know mass of the precipitate and you want to calculate mass of the determined substance, you just multiply mass of th epreicipitate by the gravimetric factor.

Think if it helps you to solve rest of the question. Think about ratios of masses and numbers of moles of substances you deal with.
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