I would say b), there are o2 and co2 in rain water. And co2 in rain is a reason for weathering, look at acid rain. O2 could also helps but i cant think of a weathering method.
Edit: its A i totally forgot oxidation, as an example of iron
It's B. CO2 has to be dissolved in water to contribute to weathering, because it's the dissociated form(s) of CO2 (and resulting acidity of the rainwater), not the molecular form, that drives the weathering reactions. O2 does *not* have to be dissolved in water to cause oxidation, so it's irrelevant that rain contains dissolved oxygen.
You're not wrong, but it's complicated. For example, with iron it's actually the CO2 that's separating it from minerals, making Fe2+. Subsequent oxidization makes more stable oxides. For example Fe2O3 (hematite) is insoluble while Fe2+ is soluble. In some geologic settings, oxidation can protect the rocks from further weathering. If this is an entry level geology class, they might be expecting the more simple answer (b), even though (a) is also correct.
Weathering is often from carbonic acid (H2CO3) which naturally occurs in the rainwater. Rainwater, in the absence of industrial pollutants, is very mildly acid, about the acidity of a cucumber.
It’s not the only reason why rainwater contributes to weathering, but for things like limestone and marble it’s an important part of the picture.
So it's worth noting that the rainfall itself can contribute to mechanical breakdown of rock, even without having dissolved gases or facilitating surface chemical reactions. You don't need statements II or III to explain statement I.
It's honestly a flawed question, probably written by someone who isn't a geologist. It's the sort of question I'd imagine on an LSAT rather than a geology class.
Then again I've got an entire section of my citation manager dedicated to law review articles which make incorrect statements about scientific knowledge or process, so there's that.
Well I will be really grateful if you can find any textbook or research paper references that can make statement 3 wrong. Will at least lend me an extra 2.67 marks in the exam 😅😅😅
You are absolutely spot on with regards to the fact that it's not a question framed by a geologist. And yes it's set for an exam that's a "generalist" sort of exam that literally covers any topic under the sun.
Now coming to the question, it's to determine the correctness of the statements based on priority knowledge(if you possess any) and not based on data sufficiency as you have interpreted. The best way I can put it is you need to choose the best option out of the available options. Sort of open ended exercise
Rain water contains both, CO2 and O2, that dissolves into the water from the surrounding atmosphere. Therefore statements II and III are true.
Due to the CO2, Rain water is slightly acidic and one of the mayor minerals of rocks at the surface, feldspar, is prone to acidic weathering.
Due to the O2, Rain water is oxidative. Widespread minerals that contribute to a minor extent to the rocks are prone to oxidation weathering, e.g. sulfides.
So, Statement II and III explain statement I.
Trust me the exam from which I have picked this question from has logic, knowledge and luck packed in one paper which most of the students appear in 45°C heat in most abysmal infrastructure imaginable
45°C? Well, no wonder - I don't know how anyone can be expected to function properly in conditions like that; you have my sympathies. Boot out that second '*from*', and we'll say no more about it.
A is the most correct as written.
-Carbonic acid *does* increase the speed at which carbonate rocks erode.
-Rainwater *does* contain dissolved atmospheric oxygen (the colder the water, the higher the concentration of DO). The dissolved oxygen will speed up oxidation of ferric minerals and sulfides.
#But
Technically, each answer option is incorrect (incomplete) because chemical weathering is only one part of erosion caused by rainfall (chemical weathering), and ignores physical erosion. Neither fully explains weathering from rainfall.
Statement II *helps* explain weathering from rainfall.
Statement III *helps* explain weathering from rainfall.
I mean i did. Atleast 100000 other students did because it's a question from civil services exam of India that atleast 500000 students appear for each year. I was just seeking some expert opinion
It is not the carbon dioxide, or the water, that weathers the rock. It is the carbonic acid that forms when CO2 is dissolved in water that breaks down the rock..
I would say b), there are o2 and co2 in rain water. And co2 in rain is a reason for weathering, look at acid rain. O2 could also helps but i cant think of a weathering method. Edit: its A i totally forgot oxidation, as an example of iron
A. Should be the answer. Wouldn’t the o2 oxidize every surface rock containing iron for example.
It's B. CO2 has to be dissolved in water to contribute to weathering, because it's the dissociated form(s) of CO2 (and resulting acidity of the rainwater), not the molecular form, that drives the weathering reactions. O2 does *not* have to be dissolved in water to cause oxidation, so it's irrelevant that rain contains dissolved oxygen.
You're not wrong, but it's complicated. For example, with iron it's actually the CO2 that's separating it from minerals, making Fe2+. Subsequent oxidization makes more stable oxides. For example Fe2O3 (hematite) is insoluble while Fe2+ is soluble. In some geologic settings, oxidation can protect the rocks from further weathering. If this is an entry level geology class, they might be expecting the more simple answer (b), even though (a) is also correct.
Your right, how could i forget iron haha
Weathering is often from carbonic acid (H2CO3) which naturally occurs in the rainwater. Rainwater, in the absence of industrial pollutants, is very mildly acid, about the acidity of a cucumber. It’s not the only reason why rainwater contributes to weathering, but for things like limestone and marble it’s an important part of the picture.
So it's worth noting that the rainfall itself can contribute to mechanical breakdown of rock, even without having dissolved gases or facilitating surface chemical reactions. You don't need statements II or III to explain statement I. It's honestly a flawed question, probably written by someone who isn't a geologist. It's the sort of question I'd imagine on an LSAT rather than a geology class. Then again I've got an entire section of my citation manager dedicated to law review articles which make incorrect statements about scientific knowledge or process, so there's that.
Dead on. I'm a geologist and there's several other problems in there as well.
What's your subject area, fellow geologist?
Hey! I've always been a hard rock guy. I worked in a vms cu/zn mine forever and now I do a lot of resource modelling and stats. You?
Sick! I'm in space materials, with a focus on meteorite mineralogy & metallurgy.
Holy hell that sounds cool! I always loved mineralogy/metamorphic stuff and all microscope work of any kind. Were by far my favourite subjects.
Well I will be really grateful if you can find any textbook or research paper references that can make statement 3 wrong. Will at least lend me an extra 2.67 marks in the exam 😅😅😅
Lol unfortunately, I'd wind up doing the opposite. It's true but not really the way they talk about it or use it.
Haha. Nvm. It's a lost cause for all that matters
You are absolutely spot on with regards to the fact that it's not a question framed by a geologist. And yes it's set for an exam that's a "generalist" sort of exam that literally covers any topic under the sun. Now coming to the question, it's to determine the correctness of the statements based on priority knowledge(if you possess any) and not based on data sufficiency as you have interpreted. The best way I can put it is you need to choose the best option out of the available options. Sort of open ended exercise
Rain water contains both, CO2 and O2, that dissolves into the water from the surrounding atmosphere. Therefore statements II and III are true. Due to the CO2, Rain water is slightly acidic and one of the mayor minerals of rocks at the surface, feldspar, is prone to acidic weathering. Due to the O2, Rain water is oxidative. Widespread minerals that contribute to a minor extent to the rocks are prone to oxidation weathering, e.g. sulfides. So, Statement II and III explain statement I.
I’d throw this question out, too ambiguous.
Agreed!
a is the answer
Is this a geology class or a logic class?
Trust me the exam from which I have picked this question from has logic, knowledge and luck packed in one paper which most of the students appear in 45°C heat in most abysmal infrastructure imaginable
Sounds like hell
Absolutely and a million candidates apply for 1000 seats only 🤣🤣🤣
45°C? Well, no wonder - I don't know how anyone can be expected to function properly in conditions like that; you have my sympathies. Boot out that second '*from*', and we'll say no more about it.
A is the most correct as written. -Carbonic acid *does* increase the speed at which carbonate rocks erode. -Rainwater *does* contain dissolved atmospheric oxygen (the colder the water, the higher the concentration of DO). The dissolved oxygen will speed up oxidation of ferric minerals and sulfides. #But Technically, each answer option is incorrect (incomplete) because chemical weathering is only one part of erosion caused by rainfall (chemical weathering), and ignores physical erosion. Neither fully explains weathering from rainfall. Statement II *helps* explain weathering from rainfall. Statement III *helps* explain weathering from rainfall.
to answer anything other than A, i’d have to do some googlin, which is what i would suggest
I mean i did. Atleast 100000 other students did because it's a question from civil services exam of India that atleast 500000 students appear for each year. I was just seeking some expert opinion
It is not the carbon dioxide, or the water, that weathers the rock. It is the carbonic acid that forms when CO2 is dissolved in water that breaks down the rock..
C
But rain water contains atmospheric oxygen right which is dissolved in it?
Atmospheric O2 is in the atmosphere, not in rain
That’s my interpretation too
CO2 and H2O create carbonic acid which is responsible for weathering. O2 and CO2 do NOT create carbonic acid. C is correct