A compound contains 2.8% Fe by mass.If the compound contains single Fe atom in its one molecule, then the molar mass(g/ml) of the compound is? (Fe=56 amu)

Question

The answer is 2000.

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Answer 1 · 2018-03-06T04:17:14

You get 2,000 by basically dividing then multiplying.

If iron, with 56 amu, therefore 56 grams/mol, composes 2.8% of the mass, then for every 2.8% of mass, 56 grams/mol is added to the molar mass.

#100/2.8 = 35.714~#

That means about 35.714 2.8 percents in the whole compound, so multiply 56 by 35.714~.

#56 * 35.714~ = 2000#

Therefore, molar mass of 2,000 grams/mol.

Answer 2 · 2018-03-06T12:59:39

The molar mass of the compound is 2000 g/mol.

Let's do this by the unitary method.

#"2.8 % of the molecular mass = 56 u"#

#"1 % of the molecular mass" = 56/2.8color(white)(l) "u"#

#"100 % of the molecular mass" = 100 × 56/2.8 color(white)(l)"u" = 2.0 × 10^3 color(white)(l)"u or 2000 u"#

If the mass of one molecule is 2000 u, the mass of one mole is 2000 g.