Homework Help

Please explain the answer to the following question in detail.If you have 1. 0 kg of...

user profile pic

adolphina | Student, Grade 9 | Honors

Posted November 24, 2010 at 4:53 PM via web

dislike 0 like

Please explain the answer to the following question in detail.

If you have 1. 0 kg of iron, how many atoms of iron are in it?

NB: take the atomic weight of iron to be 56.

Present your result in Scientific Notation, A x 10B, and complete the form:

A = B =

(1 significant figure for A, B a whole number)

2 Answers | Add Yours

Top Answer

user profile pic

justaguide | College Teacher | (Level 2) Distinguished Educator

Posted November 24, 2010 at 5:13 PM (Answer #1)

dislike 2 like

We need to find the number of atoms of iron in 1.0 kilogram of iron. For this we need the atomic mass of iron. As you have given, the atomic weight of iron is 56. So we can use this. The 56 represents that one mole of iron weighs 56g.

Now one mole is 6.022*10^23 atoms.

So one kilogram has 1000/ 56 moles of iron. This is 17.857 moles.

Each mole has 6.022*10^23 atoms or in total there are 17.857*6.022*10^23 atoms = 1.075*10^25 atoms.

In the notation A*10^B, we get A = 1.0 and B = 25.

Therefore the required values of A and B are 1.0 and 25 respectively

user profile pic

wisdomhunters | High School Teacher | Honors

Posted November 24, 2010 at 11:27 PM (Answer #2)

dislike 0 like

Atomic weight of iron is 56, then 56g of iron will have Avogadro number of atoms, that is 6.023 x 10^23.

Hence, 1kg of iron will have 1000g/56g x 6.023 x 10^23 atoms

or 1.075 x 10^25 atoms.

Therefore, A = 1 and B = 10^24

A=B=1( both are having only one significant figure)

Join to answer this question

Join a community of thousands of dedicated teachers and students.

Join eNotes