Chemistry help please!

[Ginofan]

I'm having a bit of trouble figuring out this problem and I've looked all throughout the chapter in my book and I still don't understand how to solve, any help would be appreciated!

There are four naturally occurring isotopes of Iron: 54Fe, 56Fe, 57Fe & 58Fe. Use the atomic mass of Iron listed on the periodic table (55.85amu) to identify the most abundant isotope.

[IceColdBrewski]

89frRi8GgGA

[robino2001]

I'm having a bit of trouble figuring out this problem and I've looked all throughout the chapter in my book and I still don't understand how to solve, any help would be appreciated!

There are four naturally occurring isotopes of Iron: 54Fe, 56Fe, 57Fe & 58Fe. Use the atomic mass of Iron listed on the periodic table (55.85amu) to identify the most abundant isotope.

The simple answer is it's 56 because it's the closest to 55.85... there really isn't much of a way to figure it out just with what they gave you. Because atomic mass is 55.85, you know the most abundant must be 54 or 56. If you look into/know about the isotopes, 54 is unstable - the others are stable... so it's 56 by process of elimination.

The typical, most often seen on test question for this is what is most abundant, the 35 or 37 isotope of Chlorine... since the atomic weight is 35.45, the answer is 35. Or you'll see what is the ratio of chlorine isotopes in nature using the 35.45 and 35/37... which is like 76% and 24%.

[Ginofan]

The simple answer is it's 56 because it's the closest to 55.85... there really isn't much of a way to figure it out just with what they gave you. Because atomic mass is 55.85, you know the most abundant must be 54 or 56. If you look into/know about the isotopes, 54 is unstable - the others are stable... so it's 56 by process of elimination.

The typical, most often seen on test question for this is what is most abundant, the 35 or 37 isotope of Chlorine... since the atomic weight is 35.45, the answer is 35. Or you'll see what is the ratio of chlorine isotopes in nature using the 35.45 and 35/37... which is like 76% and 24%.

Maybe that was why I was having so many issues with trying to figure out how to solve this thing...there's no mathematical way to, from what you're saying! This book is BS but thank you for your reply.

[resistanze]

Pretty sure there's a mathematical forumla for this, at least for two isotopes:

Isotope1 (x) + Isotope 2 (y) = atomic weight, where x + y = 1

For that question, it would be something like:

54 (w) + 56 (x) + 57 (y) + 58 (z) = 55.85

where w + x + y + z = 1

But I don't think that's solvable without more info (too many variables).

[E20]

Whichever Iron is closest to the atomic weight. So Iron 56, reason being is because the atomic weight is an average so the number closest to the average must be the most abundant because it is being factored in to the average so many times so that is why the atomic weight average is closes to Fe 56.

[Spur-Addict]

89frRi8GgGA

Three "Girth Units" :lol

[robino2001]

Whichever Iron is closest to the atomic weight. So Iron 56, reason being is because the atomic weight is an average so the number closest to the average must be the most abundant because it is being factored in to the average so many times so that is why the atomic weight average is closes to Fe 56.

I'm gonna go all geeky saying that's not necessarily true... at least the reasoning isn't. In most of the real life cases, that reasoning works (closest to the average is the most abundant). Without knowing anything about the isotopes, you can make up numbers to throw percentages together where 54, 56 or 57 are the right answer. The only way to make 54 or 57 the most abundant though is to relatively high percentages of Fe54 (40% or more) but like I said up top, that isotope is not stable at all. I'd assume the textbook expects you to know Fe54 is not stable, therefore 54 or 57 are not possible...? I guess that's what the book is aiming for.

[ploto]

Mathematically speaking, you can not say that the number closest is the most abundant.

[Cant_Be_Faded]

lol.

[Wild Cobra]

I'm having a bit of trouble figuring out this problem and I've looked all throughout the chapter in my book and I still don't understand how to solve, any help would be appreciated!

There are four naturally occurring isotopes of Iron: 54Fe, 56Fe, 57Fe & 58Fe. Use the atomic mass of Iron listed on the periodic table (55.85amu) to identify the most abundant isotope.
That's a ridiculous and impossible question to answer other than best guess.

If this is a college class you're paying for, you should demand your money back.

It can be any of the isotopes.

It can be 54 if it had about 50% of that isotope, 2% of 56, 11% of 57 and 37% of 58.

It can be 57 if it had about 40% of 57, 29% of 54, 30% of 56, and 1% of 58.

It can be 56 because it's between the two above examples.

It cannot be 58.

56 is the correct answer at 91.754%, but closest doesn't count. This isn't horseshoes. Mercury has a mass of 200.59, but isotope 202 is the most abundant at 29.86%. Isotope 200 is less, at 23.1%, then isotope 199 at 16.87%, then 201 at 13.18%. The last notable stable isotope is 204 at 6.87%.

I guess schools today are teaching phony physics to keep up with phony global warming theories.

[Wild Cobra]

What's funny, is not long before coming here, I quoted Mark Twain in the politics forum:

"I have never let my schooling interfere with my education."

[Wild Cobra]

Here’s a good one. Ask your instructor using Germanium:

There are five naturally occurring isotopes of Germanium: 70Ge, 72Ge, 73Ge, 74Ge, & 76Ge. Use the atomic mass of Germanium listed on the periodic table (72.64amu) to identify the most abundant isotope.

74Ge is the correct answer!

20.38% 70Ge
27.31% 72Ge
7.76% 73Ge
36.72% 74Ge
7.83% 76Ge

[Ginofan]

Here’s a good one. Ask your instructor using Germanium:

There are five naturally occurring isotopes of Germanium: 70Ge, 72Ge, 73Ge, 74Ge, & 76Ge. Use the atomic mass of Germanium listed on the periodic table (72.64amu) to identify the most abundant isotope.

74Ge is the correct answer!

20.38% 70Ge
27.31% 72Ge
7.76% 73Ge
36.72% 74Ge
7.83% 76Ge

Sorry for coming off as dumb, but how did you get the percentage of abundancy for each isotope?

[ploto]

Sorry for coming off as dumb, but how did you get the percentage of abundancy for each isotope?

He looked up the actual figures and showed that the closest is not always the right answer.

[spurster]

That's a ridiculous and impossible question to answer other than best guess.

If this is a college class you're paying for, you should demand your money back.

It can be any of the isotopes.

It can be 54 if it had about 50% of that isotope, 2% of 56, 11% of 57 and 37% of 58.

It can be 57 if it had about 40% of 57, 29% of 54, 30% of 56, and 1% of 58.

It can be 56 because it's between the two above examples.

It cannot be 58.

56 is the correct answer at 91.754%, but closest doesn't count. This isn't horseshoes. Mercury has a mass of 200.59, but isotope 202 is the most abundant at 29.86%. Isotope 200 is less, at 23.1%, then isotope 199 at 16.87%, then 201 at 13.18%. The last notable stable isotope is 204 at 6.87%.

I guess schools today are teaching phony physics to keep up with phony global warming theories.

I could be that something like this answer is what the teacher wants. I know it seems unfair but sometimes college teachers ask questions that don't make sense to find out which students can think, to change the "wrong" question into the "right" question. If I were Ginofan and his teacher was cool, I would be tempted to submit this thread as the answer with the statement "The question didn't make sense to me, so I asked for help on this forum." His teacher (again assuming that the teacher can laugh about things like this) can easily look at this forum to see that Ginofan isn't getting all his answers from Wild Cobra.

[Wild Cobra]

Sorry for coming off as dumb, but how did you get the percentage of abundancy for each isotope?
Wikipedia is a good source for material. However, double check things as sometimes it is in error.

wiki link: Isotope Index Page (http://en.wikipedia.org/wiki/Index_to_isotope_pages)

[to21]

I though for sure this was a Dallas Cowboys thread.

[Wild Cobra]

I could be that something like this answer is what the teacher wants. I know it seems unfair but sometimes college teachers ask questions that don't make sense to find out which students can think, to change the "wrong" question into the "right" question.
This is possible, but I doubt it. However, that is exactly what I would do. I would say pretty much like I posted, that with the data given, there are three possible answers.

I would include the radioactive one because it is a natural isotope, just like uranium. How would you answer the same question for uranium is you exclude the radioactive isotopes, since all are radioactive?

Would you exclude uranium Robino?

[ORION]

all I know is that its cool to pour bleach in the toilet and then pee in it

[robino2001]

This is possible, but I doubt it. However, that is exactly what I would do. I would say pretty much like I posted, that with the data given, there are three possible answers.

I would include the radioactive one because it is a natural isotope, just like uranium. How would you answer the same question for uranium is you exclude the radioactive isotopes, since all are radioactive?

Would you exclude uranium Robino?

I wouldn't worry too much about proving the book/professor to be wrong - most of the times the professors never really look closely at the questions in the books... I assume it's a homework problem anyway so it's not like it's life or death or you have to get exactly what the teacher wants right. I taught intro/general chem for a while and these questions are usually only asked with Chlorine and Magnesium... I wouldn't stress about it too much because at least Ginofan realized there was something afoul with the question which at least shows an understanding. If there is a similar question on a test, I'd almost put money on it being much clearer and being on Chlorine.

[SequSpur]

baseline bum is a master of this stuff.

[baseline bum]

Nah man, I suck at chemistry. My old chemistry textbook is full of bad problems like that one though.

[PakiDan]

eHarmony.com promises perfect chemistry.

[Wild Cobra]

I wouldn't worry too much about proving the book/professor to be wrong - most of the times the professors never really look closely at the questions in the books... I assume it's a homework problem anyway so it's not like it's life or death or you have to get exactly what the teacher wants right. I taught intro/general chem for a while and these questions are usually only asked with Chlorine and Magnesium... I wouldn't stress about it too much because at least Ginofan realized there was something afoul with the question which at least shows an understanding. If there is a similar question on a test, I'd almost put money on it being much clearer and being on Chlorine.
Maybe you should apply some of your understanding of the sciences to the Global Warming threads in the political forum.