DAT- Gen. Chem question

[SpikeyMike83]

if you've taken the DAT....

how much of the general chemistry section has questions with answer choices like this?

35mL of .10M KOH is required to neutralize 50 mL of a monoprotic acid solution. The molarity of the acid solution is:

A. (35)(50)(.10)
B. (35/.10)(50)
C. (50/35)(.10)
D. (35/50)(.10)
E. (50/.10)(35)

this one is fairly simple, but when they put the answer choices like this it throws me off. As you're aware there isn't time to calculate out every choice to see if it matches up to what you get... so any way that I can understand this better? It's my stellar math skills shining through....

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[surgeon]

if you've taken the DAT....

how much of the general chemistry section has questions with answer choices like this?

35mL of .10M KOH is required to neutralize 50 mL of a monoprotic acid solution. The molarity of the acid solution is:

A. (35)(50)(.10)
B. (35/.10)(50)
C. (50/35)(.10)
D. (35/50)(.10)
E. (50/.10)(35)

this one is fairly simple, but when they put the answer choices like this it throws me off. As you're aware there isn't time to calculate out every choice to see if it matches up to what you get... so any way that I can understand this better? It's my stellar math skills shining through....

The equation that should be used I think is NA VA = NB VB
and you solving for NA the nomality or molarity since it is (monoprotic), of the acid. Which is answer B.

 

[SpikeyMike83]

its not that I can't solve the question, its just that when the answer choices are given that way they throw me off.

 

[Utes]

surgeon, correct reasoning but I believe you typo'd the answer, the answer is D.
35mL of .10M KOH is required to neutralize 50 mL of a monoprotic acid solution. The molarity of the acid solution is:
So if you're looking at NaVa = NbVb and you know it's monoprotic then 35 = Vb and .10 = Nb and 50 = Va and we're solving for Na.
so.... Na*50 = 35*.10
so divide both sides by 50 and it should be (.10)(35)/50 which would be D.

Some people have said in previous posts that the DAT doesn't calculate all the answers, it leaves some of the answer choices like the example you listed. If you can calculate that in your head though, you should be able to pick it out from the multiple choice.

 

[surgeon]

surgeon, correct reasoning but I believe you typo'd the answer, the answer is D.
35mL of .10M KOH is required to neutralize 50 mL of a monoprotic acid solution. The molarity of the acid solution is:
So if you're looking at NaVa = NbVb and you know it's monoprotic then 35 = Vb and .10 = Nb and 50 = Va and we're solving for Na.
so.... Na*50 = 35*.10
so divide both sides by 50 and it should be (.10)(35)/50 which would be D.

Some people have said in previous posts that the DAT doesn't calculate all the answers, it leaves some of the answer choices like the example you listed. If you can calculate that in your head though, you should be able to pick it out from the multiple choice.

That is correct, the answer is D I made a typo
Once the equation is set up you can eloimnate 3 choices right away. Just look where the the Acids vloume is in the denominator

 

[cowsgomoo]

if you've taken the DAT....

how much of the general chemistry section has questions with answer choices like this?

35mL of .10M KOH is required to neutralize 50 mL of a monoprotic acid solution. The molarity of the acid solution is:

A. (35)(50)(.10)
B. (35/.10)(50)
C. (50/35)(.10)
D. (35/50)(.10)
E. (50/.10)(35)

this one is fairly simple, but when they put the answer choices like this it throws me off. As you're aware there isn't time to calculate out every choice to see if it matches up to what you get... so any way that I can understand this better? It's my stellar math skills shining through....

Best way is to set up NV = NV equation and solve for N and in this case it is equal to M. don’t try to calculate. I find these questions the easiest because I hate calculating stuff when you have to estimate.

 

[Yellow-Jellow]

The answer is D,,,,here's why

Va Ma =Vb Mb
.since they gave you Va=35 , Ma = 10 , and Vb= 50...you'r searching for Mb


Va Ma...........................................................Vb Mb
----------- ============================ ------------
Vb..................................................................Vb


(35) (10)....................................................(50) (Mb)
------------- ====================== -------------- =
50...............................................................50



the 50 on top cancel out the 50 on bottom .


you end up with:-

(35) (10)
--------------- = Mb
50


Final answer = [ (35) / (50) * (10) ]

easy ....right ?!