NS5 Chem/Phys #54 *SPOILER

[Mr. otcoD]

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hey guys could you explain this to me please?
NS explanation is that a Potassium ion (39 amu) is smaller than oxygen (32 amu) but I don't understand this.

 

[YayPudding]

In a biological system you'd see O2

 

[Mr. otcoD]

In a biological system you'd see O2

I don't understand. can you explain more

 

[YayPudding]

I don't understand. can you explain more

Although on its own Oxygen is smaller than potassium, in a biological environment, you would have oxygen bound with another oxygen (O2) and thus it would be much larger than a single K+ ion. Also narrow things down by using the information in the question. Sodium and chloride are key players in axons and membrane potentials, so that can help narrow it down to 50/50

 

[aldol16]

In a biological system you'd see O2

I don't understand. can you explain more

In any system, you will see O2. You never see oxygen atoms or O2- floating around. They are far too unstable.

 

[YayPudding]

In any system, you will see O2. You never see oxygen atoms or O2- floating around. They are far too unstable.

But don't forget reactive oxygen species, which do in fact regularly appear in living beings. Such is not listed among OPs answer choices though

 

[aldol16]

But don't forget reactive oxygen species, which do in fact regularly appear in living beings. Such is not listed among OPs answer choices though

Reactive oxygen species are still two oxygens bonded together, with the exception of hydroxyl radical, which isn't an oxygen atom by any count. They are in fact common - that's why we have evolved enzymes like superoxide dismutase to get rid of them. If you had oxygen atoms floating around, that would be much more problematic than reactive oxygen species.

 

[Mr. otcoD]

Although on its own Oxygen is smaller than potassium, in a biological environment, you would have oxygen bound with another oxygen (O2) and thus it would be much larger than a single K+ ion. Also narrow things down by using the information in the question. Sodium and chloride are key players in axons and membrane potentials, so that can help narrow it down to 50/50

But isn't O2 (32 amu) still smaller than K+ (39 amu)?

 

[YayPudding]

But isn't O2 (32 amu) still smaller than K+ (39 amu)?

I would focus on the atomic radius

 

[aldol16]

But isn't O2 (32 amu) still smaller than K+ (39 amu)?

Mass =/ steric size. Van der Waals radius is the relevant measure here.

 

[sazerac]

But isn't O2 (32 amu) still smaller than K+ (39 amu)?

Which is easier to fit into your backpack, a kettle bell weighing 39 lbs or a barbell with two 16 lb weights separated by a 6 foot wooden bar?