# Chem

posted by .

1.75 x 10^25 selenium atoms contains how many moles of selenium?

• Chem -

1 mol contains 6.02E23 atoms.

• Chem -

I am still not understanding.

• Chem -

Set up a proportion if you don't understand it any other way. For example, you have 5 oranges. They weigh 8 lbs. How much does one weigh?
(8 lbs/5 oranges) = (?lb/1 orange)
Solve for ? = 8*(1/5) = 1.6 lb each.

(1.75E25 atoms/?mol) = (6.02E23 atoms/1 mol).
? mol = 1.75E23 x (1/6.02E23) = ?

Any problem that is directly proportional can be done this way. Another way is to use dimensional analysis.
You know 1 mol contains 6.02E23 atoms. You want to know how many mols in 1.l75E25 atoms.
1.75E25 x conversion factor to convert atoms to mols.
1.75E23 atoms x (1 mol/6.02E23 atoms = ?
Note that atoms in the numerator cancel with atoms in the denominator and leaves mols (w3hich is what you wanted). Dimensional analysis always works.

## Similar Questions

1. ### Chemistry

What is the valency of selenium in hydrogen selenide?
2. ### Physical Science

Compare the number of valence electrons an oxygen, O, atom has with the number of valence electrons a selenium, Se, atom has. Are oxygen and selenium in the same period or group?
3. ### chemistry

Mole and Particle practice How many representative particles (atoms, ions, molecules, etc) are present in each of the following?
4. ### Science

compare the number of valence electrons an oxygen, O, atom has with the number of valence electrons a selenium, Se, atom has. are oxygen and selenium in the same period or group?
5. ### Physical science

Compare the number of valence electrons an oxygen atom has with the number of valence electrons a selenium atom has. Are oxygen and selenium in the same period or group?
6. ### Physical science

Compare the number of valence electrons an oxygen atom has with the number of valence electrons a selenium atom has. Are oxygen and selenium in the same period or group?
7. ### chemistry

A laboratory has a 2.0-mol sample of pure selenium and a 2.0-mol sample of pure chromium. How many more grams of selenium than chromium does this represent?
8. ### Chemistry

1) What is the atomic # for selenium? 34 2) Write the full electron configuration for selenium following the (n+l) rule?
9. ### Chemistry

1) What is the charge on the ion that Selenium forms in an ionic compound?
10. ### chemistry

draw a diagram showing the arrangement of the valency electrons in one molecule of the covalent compound selenium chloride. use x to represent an electron from an atom of selenium. use o to represent an electron from an atom of chlorine

More Similar Questions