Which has the lowest molarity?

[anitra627]

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Which of the following solutions has the lowest molarity?

A. 2N H3PO4
B. 2N HCl
C. 1M H3PO4
D. 2N H2CO3


Answer's A. Can someone explain why?
Thanks.

 

[silkworm]

A: 2N = 3(H+) * Molarity
B: 2N = 1(H+) * Molarity
C: Molarity = 1
D: 2N = 2(H+) * Molarity

So A would have the lowest Molarity value

 

[anitra627]

Ok, I'm probably really brain pooping on something simple here- but isn't normality referring the number of equivalents? Doesn't a 2N solution of H3P04 have 6(H+) equivalents?

 

[anitra627]

Nevermind! Once again, I spoke too fast. I didn't realize that you were using * as a multiplication sign. A 2 MOLAR solution of H3PO4 has 6 H+ equivalents. So a 6N solution is 2/3 molar.

Thanks!

 

[MDtoBe777]

Someone explain this to me:

2N = 2(3 M)=~6M
or 6H+of equivalence.

So if it has 6H+ of equivalence why does it have a lower molarity. This is probably really dumb..but I haven't seen normality mentioned at all in the TPR workbook/review book.

So are you always looking for H+ equivalence? Or how does this work? Please help.

 

[MDtoBe777]

oh wait...

A: 2N = 3(H+) * Molarity
B: 2N = 1(H+) * Molarity
C: Molarity = 1
D: 2N = 2(H+) * Molarity


okay I see it..never mind. 2/3 would be the lowest 1..duh. But I'm confused by the last post...saying that it is a 6M solution.

 

[OHare]

It's a 2/3 molar solution, not 6

oh wait...

A: 2N = 3(H+) * Molarity
B: 2N = 1(H+) * Molarity
C: Molarity = 1
D: 2N = 2(H+) * Molarity


okay I see it..never mind. 2/3 would be the lowest 1..duh. But I'm confused by the last post...saying that it is a 6M solution.

 

[smc927]

I suppose I should be worried that I'm taking the MCAT in a few days and have no clue what you guys are talking about.

 

[spiritgirl]

Which of the following solutions has the lowest molarity?

A. 2N H3PO4
B. 2N HCl
C. 1M H3PO4
D. 2N H2CO3


Answer's A. Can someone explain why?
Thanks.

I have a very stupid question. Um, what is N?

Thanks...

EDIT: Nevermind I just looked it up: The concentration of a solution, expressed in gram equivalent weights of solute per liter of solution.

Wow I've got a long way to go...

ANOTHER EDIT: Right...? This isn't mentioned in the TPR review book as far as I know... yikes?

 

[Code Brown]

I have a very stupid question. Um, what is N?

Thanks...

EDIT: Nevermind I just looked it up: The concentration of a solution, expressed in gram equivalent weights of solute per liter of solution.

Wow I've got a long way to go...

ANOTHER EDIT: Right...? This isn't mentioned in the TPR review book as far as I know... yikes?

Easy way to remember.

1 M HCl has 1 N of H+
1 M H2SO4 has 2N of H+

 

[shaq786]

Im not taking the mcat till next year...but um yea I had no clue what N was until now. I finally gained a better understanding of it becuase the kaplan book doesnt go into the best detail on it in their review section and it was never even discussed in my chem class.

Thanks for posting the question.

 

[jon0013]

thank god i read the thread...wasnt in TPR and dont think it had examples in EK...and they say to quit SDN a week before test...

 

[Clemson Doc]

Think of normality as the number of hydrogens that a 1 M solution can donate. A 1 M H3PO4 solution can contribute 3 hydrogens (i.e., equivalents), so it is 3 N. I am pretty certain that normality can never be less than molarity. For instance, a 1 M solution of HCl is also 1 N. However, a 1 M solution of H2SO4 is 2 N.

To convert between N and M:

Assume you're given a 3 N H2SO4 solution. Divide 3 N by the number of equivalents in 1 M of H2SO4 (2 equivalents). So a 3 N solution of H2SO4 is 1.5 M.

Assume you're given a 3 M solution of HCl. Multiply 3 M by the number of equivalents in 1 M of HCl (1 equivalent). So a 3 M solution of HCl is 3 N.

I agree that Kaplan didn't cover this particularly well. Hope this helps.