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
• 9 years ago

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

• 9 years ago

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!!!!

• 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
• 9 years ago

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

• 9 years ago

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

Should be right I followed my notes.

• 9 years ago

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