Chemical Forums

Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: nothincomin on May 20, 2010, 02:42:48 PM

Title: Few Chem Questions!
Post by: nothincomin on May 20, 2010, 02:42:48 PM

Step by step answers and explanations please!

1) How many electrons would it take to the equal the mass of a proton?

2) A helium nucleus has two protons and two neutrons. How many electrons would it take to equal the mass of a helium nucleus?

Title: Re: Few Chem Questions!
Post by: sjb on May 20, 2010, 04:00:56 PM

Quote from: nothincomin on May 20, 2010, 02:42:48 PM

Step by step answers and explanations please!

1) How many electrons would it take to the equal the mass of a proton?

2) A helium nucleus has two protons and two neutrons. How many electrons would it take to equal the mass of a helium nucleus?

What is the mass of an electron? Of a proton? Of a neutron? What about binding energy?

Title: Re: Few Chem Questions!
Post by: nothincomin on May 20, 2010, 10:35:05 PM

Mass of Proton- 1.67262 X 10^-27
Mass of Electron 0.00091 X 10^-27

Mass of Proton/Mass of Electron
1.67262 X 10^-27/ 0.00091 X 10^-27= 1838.04 g
So therefore it would take 1838.04g of electrons to equal the mass of a proton. Let me know if I'm wrong.

Title: Re: Few Chem Questions!
Post by: AWK on May 21, 2010, 01:18:31 AM

Quote

So therefore it would take 1838.04g of electrons to equal the mass of a proton. Let me know if I'm wrong.

OK

Quote

1838.04 g

Should be without mass unit (g)

Title: Re: Few Chem Questions!
Post by: nothincomin on May 21, 2010, 09:53:17 PM

Quote from: nothincomin on May 20, 2010, 02:42:48 PM

Step by step answers and explanations please!

1) How many electrons would it take to the equal the mass of a proton?

2) A helium nucleus has two protons and two neutrons. How many electrons would it take to equal the mass of a helium nucleus?

For the 2nd question do I multiply 4 (protons + neutrons) X mass of electrons (0.00091 X 10^-27)?

Title: Re: Few Chem Questions!
Post by: Borek on May 22, 2010, 04:57:50 AM

Quote from: nothincomin on May 21, 2010, 09:53:17 PM

For the 2nd question do I multiply 4 (protons + neutrons) X mass of electrons

Why multiply? What will be units of your answer if you multiply mass X mass?

If I will ask you how many apples weight the same as you would you multiply your weight with apple weight?

Title: Re: Few Chem Questions!
Post by: nothincomin on May 22, 2010, 12:25:05 PM

So instead I would take mass of the helium nucleus/mass of an electron?

(2(1.67262 X 10^-27)) + (2(1.67493^10^-27))/ (0.00091 X10^-27)= 7357.25 electrons to equal the mass of the helium nucleus.

Title: Re: Few Chem Questions!
Post by: Borek on May 22, 2010, 12:47:21 PM

Close, and in general good approach, unfortunately final result is incorrect. Mass of helium nucleus is smaller than the sum of the masses of protons and neutrons, google "mass deficit".

Title: Re: Few Chem Questions!
Post by: nothincomin on May 22, 2010, 01:09:37 PM

Were you referring to the the mass of a neutron? It was a typo, fixed it now.

Title: Re: Few Chem Questions!
Post by: Borek on May 22, 2010, 01:54:31 PM

I have explained precisely what I was referring to. Have you read my post?