Chemistry Converting the number of atoms to the mass of an element

[rachelmaddiee]

Homework Statement

I need help with a question

Relevant Equations

N/A

Atoms-to-mass conversion
Step 1: First, convert the number of atoms to moles, then convert miles to grams
Step 2: Second, use the inverse of the Avogadro’s number(moles to number of atoms)

Are these the correct steps?

 

[Charles Link]

I think you have both steps in what you labeled as step 1, and they are correct. (miles=moles=spelling typo). You need to list them as two separate steps, but you should add more detail. How do you get from atoms to moles? How do you get from moles to grams? $\\$ What you labeled step 2, I believe is irrelevant. You need Avagadro's number in step 1, but you need to describe the mathematics accurately.

 

[rachelmaddiee]

I think you have both steps in what you labeled as step 1, and they are correct. (miles=moles=spelling typo). You need to list them as two separate steps, but you should add more detail. How do you get from atoms to moles? How do you get from moles to grams? $\\$ What you labeled step 2, I believe is irrelevant. You need Avagadro's number in step 1, but you need to describe the mathematics accurately.

That’s how it is written in my book

 

[rachelmaddiee]

 

[Charles Link]

Again, how do you get from x atoms to y moles? That is step 1, and it is very simple, but you need to write it out. It involves Avagadro's number, but I'm not supposed to tell you the complete answer.
The second step, going from y moles to z grams is also a simple one, but you need to write it out. It involves the atomic weight, but again, you need to write out how the z grams is computed. $\\$ These two simple calculations are used quite often. It is important for you to know them from memory. You should know them so well, that you don't need to look them up.

 

[rachelmaddiee]

Again, how do you get from x atoms to y moles? That is step 1, and it is very simple, but you need to write it out. It involves Avagadro's number, but I'm not supposed to tell you the complete answer.
The second step, going from y moles to z grams is also a simple one, but you need to write it out. It involves the atomic weight, but again, you need to write out how the z grams is computed.

Step 1 To convert from atoms to moles, divide the atom amount by Avogadro's number (6.02 x 10^23 atoms), or multiply by its reciprocal.
Step 2 To convert the moles of a substance to grams, you will need to multiply the mole value of the substance by its molar mass.
Grams * 1 mole/grams = moles

 

[Charles Link]

Very good, except for the very last line. z grams/(atomic or molecular weight)=y moles, so that $\\$ (y moles)(atomic or molecular weight)=z grams. $\\$ Or how I like to remember it from the chemistry I had in high school: "moles times molecular weight=grams".

 

[rachelmaddiee]

Very good, except for the very last line. z grams/(atomic or molecular weight)=y moles, so that $\\$ (y moles)(atomic or molecular weight)=z grams. $\\$ Or how I like to remember it from the chemistry I had in high school: "moles times molecular weight=grams".

Why does it say to use the inverse in my book?

 

[Charles Link]

Why does it say to use the inverse in my book?

It's a clumsy way to say you divide the number of atoms by Avagadro's number to get the number of moles. Dividing is the same as multiplying by the inverse. Really very clumsy.

 

[rachelmaddiee]

It's a clumsy way to say you divide the number of atoms by Avagadro's number to get the number of moles. Dividing is the same as multiplying by the inverse. Really very clumsy.

So, would I include this too?
Atoms-to-mass conversion
Step 1: First, convert the number of atoms to moles, then convert moles to grams
Step 2: Second, use the inverse of the Avogadro’s number(moles to number of atoms)

 

[Charles Link]

So, would I include this too?

Simply say you divide x atoms by Avagadro's number to get y moles. That's the process that I think most people do. It's the same as multiplying by the inverse of Avagadro's number, N−1ANA−1, but again this "inverse" explanation is too clumsy, IMO. Everyone knows NA=6.02E+23NA=6.02E+23, but I don't think too many people know what N−1ANA−1 is. They should just say " divide by Avagadro's number".

 

[rachelmaddiee]

Simply say you divide x atoms by Avagadro's number to get y moles. That's the process that I think most people do. It's the same as multiplying by the inverse of Avagadro's number, $N_A^{-1}$, but again this "inverse" explanation is too clumsy, IMO. Everyone knows $N_A=6.02 E+23$, but I don't think too many people know what $N_A^{-1}$ is.

But that is the second step? That’s why I’m confused.

 

[Charles Link]

But that is the second step? That’s why I’m confused.

That's the first step. The second step is multiply y moles by the atomic weight to get z grams. (I can't read your book=the print is too small, but this process is simple enough, that you need a book that explains it well).

 

[rachelmaddiee]

Atoms-to-mass conversion
Step 1: First, convert the number of atoms to moles, then convert moles to grams
To convert from atoms to moles, divide the atom amount by Avogadro's number (6.02 x 10^23 atoms), or multiply by its reciprocal.
Step 2: Second, use the inverse of the Avogadro’s number(moles to number of atoms)
To convert the moles of a substance to grams, you will need to multiply the mole value of the substance by its molar mass. moles x molecular weight=grams

 

[Charles Link]

"then convert moles to grams" belongs in step 2. That should replace the first line of what you have for step 2 above, which is extra and/or incorrect. With those edits, you have it correct. $\\$ Note: The inverse of Avagadro's number gets you from x atoms to y moles, when you multiply x by the inverse of Avagadro's number. It is better explained by saying you divide x atoms by avagadro's number to get y moles. That is step 1, but your explanation above is better and very complete, once you remove the "then convert moles to grams" and put it in step 2. $\\$ Meanwhile, Avagadro's number is not used in step 2. Instead, it simply uses the atomic weight or molecular weight.

 

[rachelmaddiee]

Atoms-to-mass conversion
Step 1: First, convert the number of atoms to moles
To convert from atoms to moles, divide the atom amount by Avogadro's number (6.02 x 10^23 atoms), or multiply by its reciprocal.
Step 2: Then convert moles to grams
To convert the moles of a substance to grams, you will need to multiply the mole value of the substance by its molar mass. moles x molecular weight=grams