[SimoneMeyer]

My apologies if the title make this post sound slightly odd and childish, but that is the question (well, part of it).

The full question is the following: A hot-dog contains approximately 0,450 g of sodium ions. This represents approximately 0,0196 moles of sodium. How many sodium ions are in a hot dog?

Now, I think that my problem here is context. What I find confusing is that from what I see, they have already stated that a hot dog has 0,450 g of sodium ions. Then why would they ask us what they have already stated?

Do they maybe want me to  tell them the exact amount of ions in a hot dog, and if you, how could I do that if they gave me an approximation of how many moles there are in a hot-dog?

I know that none of you can read the teacher's mind, but is it possible that you can see a different side to the question that I can't?

Thank you for your time, it's greatly appreciated as always.

[sjb]

Perhaps it's an exercise in significant figures or similar?

If you had 1.00 mol of sodium ions, how many actual sodium ions would you have? 1, 10, 100, 2654246, ...?

[SimoneMeyer]

I had spoken to my father about this question and he has guessed the same thing. The only problem is that I am at the second unit right now and in this book they do not speak of significant numbers, that was in the first book/unit. Unfortunately, the only book that would ask questions regarding significant numbers would be the first unit/book.

[renge ishyo]

There are 6.022x10^-23 ions in a mole of ions. Using that you can figure it out...

[SimoneMeyer]

I know how many ions are in a mole. My problem is figuring out what they are asking of me.

[renge ishyo]

The question wants to know how many ions are in 0.0196 moles. You know how many ions are in one mole, so how do you calculate how many ions are in 0.0196 moles? That will get you to the answer.

[SimoneMeyer]

But why would they tell me that there are a certain amount of ions in a hot-dog if it's incorrect? It confuses me.

[renge ishyo]

You might just be getting confused because you've thought about things too much (I used to do that too when I was a beginning chem student). Here's the question again so you can look at it in isolation.

A hot-dog contains approximately 0.450 g of sodium ions. This represents approximately 0.0196 moles of sodium. How many sodium ions are in a hot dog?

They have already done one calculation for you by converting the weight of sodium ions in grams into moles. Now they want you to convert the moles into ions. The number of ions and "grams" are not the same thing...for instance, one mole of carbon atoms has 6.022x10²³ atoms in it and weighs 12g. I think the confusion is you are getting the number of ions confused with the weight of the ions?

[sjb]

There are 6.022x10^-23 ions in a mole of ions. Using that you can figure it out...

That should be 10⁺²³, no?

But why would they tell me that there are a certain amount of ions in a hot-dog if it's incorrect? It confuses me.

Whilst you are right in that 0.0196 moles is an exact number, perhaps think of it like "If you have 8 dozen eggs, do you have more or less than 100 eggs?" Are you perhaps confusing moles and molecules?

[renge ishyo]

That should be 10+23, no?

That is correct sir.

Blasted chemistry always makes me so negative exponent happy, but in this case it should be a positive exponent.

[SimoneMeyer]

I think that it was a comprehension problem on my part. Because it's an ILC course I can't really contact a teacher and ask them what they want so when I answer questions I'm going by what I think that they want (so I usually ask others for their opinions).

Thank you so much for helping me out with it, otherwise I don't know what kind of off-base calculations I'd be doing right now. I think that my problem was confusing the ions weight with the number of ions.