I need to find the mass of an element that is in cubic cm!!!

Questions and answers on how to convert things from one unit or system to another

Moderator: convert-me.com

I need to find the mass of an element that is in cubic cm!!!

Postby mommyto3girls » Tue Mar 30, 2004 6:20 am

I need to find the mass of the element Neodymium that is 1000. cubic centimeters. I am not sure how to do this can anyone elp? PLEASE!!!!!! I also need to figure out the # of atoms and the # of mole if anyone can help there. Thanks
mommyto3girls
 
Posts: 1
Joined: Tue Mar 30, 2004 6:16 am
Location: South Carolina

Postby shill » Tue Mar 30, 2004 7:18 am

The mass of Neodymium is 144.24 u, according to this web page. One mole of Neodymium has a mass of 2.39516001 × 10^-25 kg according to Google calculator. The density of solid Neodymium is 6800 kg/m³ according to this web page. That converts to 6.8 × 10^8 kg/cm³ (kilograms per cubic centimetre). m = D/v, therefore (6.8 × 10^8 kg/cm³) / (1000 cm³) = 680 000 kg.
shill
Expert
 
Posts: 91
Joined: Fri Feb 06, 2004 8:22 am

Re: I need to find the mass of an element that is in cubic c

Postby Knight » Mon Apr 19, 2004 5:45 am

mommyto3girls wrote:I need to find the mass of the element Neodymium that is 1000. cubic centimeters. I am not sure how to do this can anyone elp? PLEASE!!!!!! I also need to figure out the # of atoms and the # of mole if anyone can help there. Thanks

As Shill pointed out, the density of Neodymiun is 6,800 Kg/m³, however, to convert Kg/m³ to g/cm³, the process is:

Code: Select all
6,800 Kg x 1,000 g/Kg = 6,800,000 g
---------------------------------------
1 m³ x 1,000,000 cm³/m³ = 1,000,000 cm³


Code: Select all
6,800,000 g
------------- = 6.8 g/cm³
1,000,000 cm³


We have 1000 cm³, so 6.8 g/cm³ x 1000 cm³ = 68,000 g or 68 Kilograms.

The answers to the last two questions are closely tied together. They hinge on the value of the mole. the mole is one of the seven basic definitions of the SI system, and is defined as: "The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon-12."

Now, The number of atoms in 0.012 kg of carbon-12 is 6.0221367 x 10²³ - This number was named "Avogadro's number" in honor of Amedeo Avogadro, who's work lead to the definitition of this value.

Now, science mumbo-jumbo aside, this means that a mole is the quantity of a substance whose weight in grams in equal to the molecular weight of the substance. In other words, a mole of one thing has Avogadro's number of that thing in it. A mole of flowers is 6.0221367 x 10²³ flowers. Not a good unit for measuring large things, but a great unit for measuring tiny things - Like so:

The weight of your 1,000 cm³ block of Neodymium is 68,000 grams.

In order to find the number of moles, we need to know the atomic weight of neodymium. We can look that up in just about any periodic chart, and get a value of 144.24 grams.

Now, since a mole is the quantity of a substance whose weight in grams in equal to the molecular weight of the substance, then we need to divide the number of grams we have, by the molecular weight, in grams, and we'll find out how many moles we have:

Code: Select all
68,000 g
------------- = 471.43 mol
144.24 g/mol


There. You've got 471.43 moles of Neodymium.

Next, since we know that one mole is equal to Avogrado's number of molecules:

471.43 mol x 6.022x10²³ atoms/mol = 7.829x10^26.

471.43 moles means that You've got 782,300,000,000,000,000,000,000,000 atoms. As you can see, it's much easier to say that that you've got 471.43 moles of Neodymium.
William J. Knight
Health Physicist
Los Alamos National Labs
User avatar
Knight
Expert
 
Posts: 309
Joined: Tue Jan 13, 2004 9:43 pm
Location: Los Alamos, NM


Return to How to convert?

Who is online

Users browsing this forum: No registered users and 3 guests

Our Privacy Policy       Cooking Measures Converter       Metric conversions