Titrations on the DAT

[Avery07]

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So I've spent the last couple hours reviewing titrations and I want to jump off a cliff.

The AADSAS guide doesn't say anything about titrations but I wanted to review them just in case. The only problem I have now is that these problems seem to be way to complex to work out for something like the DAT.

Anyone have an idea as to if these questions will show up?

As in:

It takes 52.6mL of a 0.724M solution of KOH to titrate 86.8mL of a solution of HNO3. What is the molar concentration of the HNO3 solution?

52.6mL KOH (1L/1,000mL)(0.724M/1L)(1 mol HNO3/1 mol KOH) = 0.0381 mol HNO3

0.0381 mol HNO3 (1L/1 mol HNO3)(1,000mL/1L)(1/868mL) = 0.0438M HNO3


Problems like this are practically impossible in your head and I hope that none of you have ever seen titrations on the DAT.

 

[UndergradGuy7]

So I've spent the last couple hours reviewing titrations and I want to jump off a cliff.

The AADSAS guide doesn't say anything about titrations but I wanted to review them just in case. The only problem I have now is that these problems seem to be way to complex to work out for something like the DAT.

Anyone have an idea as to if these questions will show up?

As in:

It takes 52.6mL of a 0.724M solution of KOH to titrate 86.8mL of a solution of HNO3. What is the molar concentration of the HNO3 solution?

52.6mL KOH (1L/1,000mL)(0.724M/1L)(1 mol HNO3/1 mol KOH) = 0.0381 mol HNO3

0.0381 mol HNO3 (1L/1 mol HNO3)(1,000mL/1L)(1/868mL) = 0.0438M HNO3


Problems like this are practically impossible in your head and I hope that none of you have ever seen titrations on the DAT.

The are easy. It is just basic stiochiometry.
For example:
It takes 52.6mL of a 0.724M solution of KOH to titrate 86.8mL of a solution of HNO3. What is the molar concentration of the HNO3 solution?

millimoles of KOH (if you leave it in millimoles it makes it easier/less work, dividing everything by 1000 is useless and a waste of time then you have to deal with decimals) = (52.6)(0.724M) = 38.0824 mmoles
KOH has 1 OH- and HNO3 has 1 H+ so they react 1:1. So moles of KOH used = moles of HNO3 used. So if we have 38.0824 millimoles of KOH = 38.0824 millimoles of HNO3.

If you know the moles of HNO3 then you can find the concentration since they gave you the volume. Moles/Volume = Concentration

So all we did was one multiplication to find the moles and then divided at the end to find the concentration.

I always thought the dat would use numbers that would divide/multiply easily. Like 1 M, 10 mL, etc. These practice exams use random numbers. As long as you know how to do it you are OK. Right? Can someone who took the dat confirm they use easier numbers to divide/multiply?

 

[AmpedUp]

I had one on my DAT...and it wasn't 1:1.

 

[OU11BB]

Is this not just m1v1=m2v2??? also if there happened to be a 2:1 base to acid ration how does this change, if you use m1v1=m2v2 you are screwed right?"

 

[Avery07]

I had one on my DAT...and it wasn't 1:1.

The ration shouldn't be hard to figure out. Were the numbers easy to divide or multiply?

 

[AmpedUp]

The ration shouldn't be hard to figure out. Were the numbers easy to divide or multiply?

Yeah, they were whole numbers. I think it was 1:2 ratio (off the top)...Find some practice in your Destroyer or Kaplan Subject Tests and (I'm pretty sure) you'll get the hang of it.

 

[OU11BB]

Yeah, they were whole numbers. I think it was 1:2 ratio (off the top)...Find some practice in your Destroyer or Kaplan Subject Tests and (I'm pretty sure) you'll get the hang of it.

is that a normality problem

 

[AmpedUp]

is that a normality problem

nope. it was not.

 

[AmpedUp]

here's some nice problems to look at...

http://www2.ucdsb.on.ca/tiss/stretton/chem2/acidwk05.htm

 

[Avery07]

is that a normality problem

What's a normality problem?

 

[OU11BB]

What's a normality problem?

30 ml of .2 M Ba(OH)2 is required to neutralize 25 ml of citric acid H3C6H5O7. what is the molarity of citric acid solution.

 

[Maygyver]

We can use the dry erase board for the science sections right?

 

[AmpedUp]

We can use the dry erase board for the science sections right?

You can use it for all sections. They won't take it away.