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Hydrofluoric acid is a substance used to etch glass. Determine the mass of 4.95 x 10^25...

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persianimmortal | Student, Grade 10 | Valedictorian

Posted March 10, 2013 at 5:03 AM via web

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Hydrofluoric acid is a substance used to etch glass. Determine the mass of 4.95 x 10^25 HF molecules?

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted March 10, 2013 at 5:14 AM (Answer #1)

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The molar mass of a chemical substance is the mass of 6.022*10^23 elementary units. Hydrofluoric acid is made of molecules with chemical formula HF that have one atom of hydrogen and one atom of fluorine. The molar mass of hydrogen is 1 g/mole and the molar mass of fluorine is 19 g/mole. The molar mass of HF is 20 g/mole. Each set of 6.022*10^23 molecules of HF have a mass of 20 g.

The mass of 4.95*10^25 molecules is given by the expression (4.95*10^25/6.022*10^23)*20 which is equal to 1643 g

The mass of 4.95*10^25 HF molecules is 1.643 kg.

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