quick chem question Options

[batman]

I must be too tired or something. Seriously. I'm going through old chem quizzes to review for the cumulative exam. On the very first quiz, I got one question wrong and I can't seem to figure it out. I'd email my TA, but he most likely wont get back to me on time.

Anyways, it's a standard (C1)(V1) = (C2)(V2) equation.

You're preparing a diluted solution: 200 mL of .096 M solution. Your stock solution is 1.6 M (error +/- 0.1). The pipette available is 10.0 +/- 0.1 mL. What's the volume of stock solution needed?

So it's basically (.096 M)(200 mL) = (1.6 M)(x volume of stock solution needed)

Right?

Am I completely blanking out? Because when I solve for that, I'm getting 12.0 +/- 0.2 mL needed and the correct answer is supposed to be 15.0 +/- 0.2 mL.

[batman]

hehe I figured it out. Apparently, we're making 200mL solution, but we're using a 250mL volumetric flask (which I left out of the original post bc I didn't think it was important, lol), which only has one line at the 250 mark. So I was supposed to use "250" for v2 instead of "200." I love my roommate.

Arright, this can be closed, etc.

[Jenni]

hehe I figured it out. Apparently, we're making 200mL solution, but we're using a 250mL volumetric flask (which I left out of the original post bc I didn't think it was important, lol), which only has one line at the 250 mark. So I was supposed to use "250" for v2 instead of "200." I love my roommate.

Arright, this can be closed, etc.

well at least u got it withought our help i think