Anonymous
Anonymous asked in Science & MathematicsMathematics · 9 years ago

# Hard Chemistry Question 10 points best answer?

Heres the question from my General Chemistry Class.

10. One atom of an unknown element (monatomic) is found to have a mass of 1.79 * 10^-23 grams, what is the molar mass (specify units) and identify the element.

I checked my lecture but I can't find any formuals to solve molar mass based off the mass alone without the element's atomic mass. Am I missing something in the question or is it impossible. Please solve if it's possible. Thanks.

Relevance

first we must find the number of moles so to do that we use the equation: n (moles) = N (number of entities of that element = 1)/Na (avogadro's number = 6.022*10^23)

so n=1/6.022*10^23

n=1.66*10^-24

now that we know the number of moles and the mass, we can use the equation n(moles=1.66*10^-24) = m (mass in grams = 1.79*10^-23)/Mr (molar mass)

Mr=1.79*10^-23/1.66*10^-24

Mr=10.8 g/mol

now by simply looking at a periodic table, we can see that this is approximately the same as boron's atomic mass (different because of rounding) so we have our mystery element: Boron (B) and its atomic weight or molar mass of 10.8 g/mol

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• There are 6.02 * 10^23 atoms in one mole of a substance

1 atom has a mass of 1.79 * 10^(-23) grams

1 mole of the atoms has a mass of:

1.79 * 10^(-23) * 6.02 * 10^23 =

1.79 * 6.02 =

10.7758

Looking at the Periodic Table of Elements, we find that Boron has an AMU (the mass of 1 mole of an element) 10.8

We have found Boron

This answer has been brought to you by...MOLTEN BORON!!

NOBODY DOESN'T LIKE MOLTEN BORON!!!!

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• Anonymous
9 years ago

We're given the mass for 1 atom. 1 mole is 6.02 * 10^23 atoms (Avogadro's number). Use dimensional analysis to solve for the molar mass.

[(1.79 * 10^-23 grams) / 1 atom] * [(6.02 * 10^23 atoms) / 1 mole)] =

10.78 grams/mole

Upon looking at the periodic table you should realize that this mass is closest to Boron's mass of 10.81 grams/mole.

Element: Boron (B)

Source(s): A+ in AP Chemistry 800 on the Chemistry SAT II
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• You can solve for the atomic mass thus...

a mole of atoms = 6.02 x 10^23 atoms/mole, x 1.79 x 10^-23 g/atom, = 10.775 grams/mole = molar mass

Closest I can find on the Periodic table is Boron at 10.811 grams/mole

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• It has a molar mass of 10.779 grams. The element is Boron from my calculations.

Should be right I followed my notes.

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• mass of atom X avogadro constant = relative atomic mass

so...(1.79 x10^-23) x (6.022x10^23)

1.79 x 6.022 = 10.78

Boron (10.81) comes the closest

units would be g/mol

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• there is no known formula. it is like a black hole, where supposedly nothing can escape. if you believe the black hole THEORY, then what is a QUASAR?

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