Gen Chem problem, please help!

[Msmouth]

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The Topscore solution doesn't help at all

In order to reach the = point, what volume of a 5M NaOH solution is needed to titrate 0.25 L of a 4M solution of HCl?

Answer is 0.2L

Thanks for your help!

I've watched Chad so many times but titration still kills me.

 

[Ferneezy]

without typing out a huge answer. essentially you're looking at a strong base vs. a strong acid which neutralize each other one to one.

1) calculate mols H+ in .25L 4M HCL (this will be how many mols OH- you need)

2) calculate volume of 5M NaOH required to deliver required mols of OH- to neutralize H+ (calculated above)

3) Profit!

 

[aqz]

Just like to add that because this is a strong acid-strong base titration...you're essentially using:

M1V1 = M2V2

Since the amount of acid must equal the amount of base.

 

[Msmouth]

Thank you, I didn't realize it was that simple! My test is Friday and I don't feel confident. My last topscore, I ran out of time because I spent too much time in gen chem....I had 14 minutes left for orgo.
At least now I know I need to move faster and I hope there aren't as many calculations on the real thing.

 

[aqz]

How are you with biology? It might be wise to cut down on your biology time instead of gen chem. Personally, I plow through bio in under 20 minutes to give myself ample time for GC and OC.

 

[Msmouth]

I think I went quickly through bio but I wasn't watching the time. According to my pace setter I was ahead of the game when I got to gen chem. I took too much time with some gen chem questions then with orgo I had so little time that I had to guess on the last 5 questions.
It sucked but it made me painfully aware that I need to step up my pace and watch that I leave myself at least 25 minutes for orgo.

I am scared but I know I've truly done my best with studying. Hopefully this exam will show that.

Edit: just to add...I think I'm good with bio. I've done all of the bio qvaults and I average about 20, on topscore it's more like 18.

 

[aqz]

Ok, that's about how I was doing on qvault + topscore.

Yeah, I think all you need to work on is your pace then.

 

[Msmouth]

Thanks so much for your advice!

 

[toyotasupra]

Best way to do it without getting confused.

4 HCl Mol/L * .25L = 1 Mol H+ ions

So now you need to balance out the 1 Mol of H+ ions with 1 Mol of -OH ions to NEUTRAL IT OUT! lol.

So just setup a easy equation. X is the volume you are seeking.

5 Mol/L NaOH * X = 1 Mol

X = 1/5 or .2 Liters