How to prepare this NaCl solution

[suhshi]

15. A student wants to prepare 250. mL of 0.10 M NaCl solution. Which procedure is most appropriate? (The molar mass of NaCl is 58.4 g mol¯1)
(A) Add 5.84 g of NaCl to 250. mL of H2O
(B) Add 1.46 g of NaCl to 250. mL of H2O
(C) Dissolve 5.84 g of NaCl in 50 mL of H2O and dilute to 250. mL.
(D) Dissolve 1.46 g of NaCl in 50 mL of H2O and dilute to 250. mL.

whats the difference btw B and D?

answer is D by the way

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[hausee]

add all Nacl to 250ml H2O will change the final volume(suppose to be 250 ml), which in turn affect final concentration.

 

[doc3232]

15. A student wants to prepare 250. mL of 0.10 M NaCl solution. Which procedure is most appropriate? (The molar mass of NaCl is 58.4 g mol¯1)
(A) Add 5.84 g of NaCl to 250. mL of H2O
(B) Add 1.46 g of NaCl to 250. mL of H2O
(C) Dissolve 5.84 g of NaCl in 50 mL of H2O and dilute to 250. mL.
(D) Dissolve 1.46 g of NaCl in 50 mL of H2O and dilute to 250. mL.

whats the difference btw B and D?

answer is D by the way

This won't come up on the actual DAT. Only thing I see is one says add and the other says Dissolve. Adding it isn't technically dissolving it.

Actually, now I got it: Adding the solid straight up will change the volume. Hence, you have to start with a lesser volume then dilute exactly to 250. Answer B will have about 251 mL which is not what we want.

EDIT: Basically explaining what Haus said.

 

[Pat Kelly]

-jackass mode-

So you took your undergrad in microbio, worked on research that resulted in a publication, and you still don't know how to prep a solution correctly? didn't your TA tell you the difference in your general chem lab or hell any lab in general? 😕

 

[sixkiller]

Harsh man...

 

[suhshi]

-jackass mode-

So you took your undergrad in microbio, worked on research that resulted in a publication, and you still don't know how to prep a solution correctly? didn't your TA tell you the difference in your general chem lab or hell any lab in general? 😕

haha first i just switched to microbio and i havent taken any lab classes for it.
research i did had nothing to do with titrations, mostly did analysis of computer data and extractions of proteins, and last time i dd any dilutions or any gchem was freshman year

no one asked for you opinion but thanks for pointin that out

 

[jrobb220]

haha funny I work in a lab and just the other day I was making a 10M TBS buffer for westerns. and I definitely just added NaCl into tris and HCl. Guess I did it wrong!

 

[solstice]

-jackass mode-

So you took your undergrad in microbio, worked on research that resulted in a publication, and you still don't know how to prep a solution correctly? didn't your TA tell you the difference in your general chem lab or hell any lab in general? 😕

HAHA now this is funny. You give more credit to undergrad than u should!
Most of TAs I had were imported from other countries and could not speak in clear English and we all looked at each other in class and somehow learned somethings. Then come your lab courses. Hmmm my Microbiol lab did not have anything about titration and these stuff and biochem lab was not required