Homework Help: chemistry

Posted by Jessica on Tuesday, April 1, 2008 at 11:53pm.

Let me repost the important information only:

Purpose: The purpose of this experiment is to determine the Ksp for calcium hydroxide.

Materials are:
*50.0 mL of 0.10 M HCl(aq)
*bromophenol blue indicator
*50.0 mLsaturated calcium hydroxide
*50.0 mL buret
*125 mL Erlynmyer Flask
*50.0 mL of distilled water
*10.0 mL pipet with pump
*waste beaker

The procedure for the lab is:
1.Fill the buret with the acid solution.
2.Pipet 10.0 mL of calcium hydroxide into the flask.
3.Add approximately 10.0 mL of water to the flask.
4.Add 4 drops of bromophenol blue to the flask.
5.Titrate the base to an endpoint and record the volume of acid added.
6.Dispose of the flask contents into a waste beaker.
7.Repeat steps 2-6 four more times.

The following is what I am having trouble with.

Present your data in a table.Use the following table as a guide:
Trial 1 Trial 2 Trial 3
*Initial volume
of HCL(mL)

*Final volume
of HCL (mL)

*Volume of
HCL added (mL)

I am having difficulty regarding the trial 1 column. What is my initial volume of HCL(mL) supposed to be?

chemistry - Jessica, Tuesday, April 1, 2008 at 11:53pm
Regarding the table, trial 1, trial 2 and trial 3 are not so neatly written but they should be shifted a little to the right
chemistry - DrBob222, Wednesday, April 2, 2008 at 12:02am
I answered this at the original post. If you still have questions, repost here.
- chemistry - Jessica, Wednesday, April 2, 2008 at 12:28am
  Here are my results:
  
  *Initial volume
  of HCL(mL)
  Trial 1- 0.0
  Trial 2- 2.51
  Trial 3- 4.95
  Trial 4- 7.4
  Trial 5- 9.9
  
  *Final volume
  of HCL (mL)
  Trial 1- 2.51
  Trial 2- 4.95
  Trial 3- 7.4
  Trial 4- 9.9
  Trial 5- ?
  
  *Volume of
  HCL added (mL)
  Trial 1- 2.51
  Trial 2- 2.44
  Trial 3- 2.45
  Trial 4- 2.50
  Trial 5- ?
  
  How would I get Final volume of HC (mL) and Volume of HCL added (mL) for trial 5?
- chemistry - Jessica, Wednesday, April 2, 2008 at 1:59pm
  When I have the table filled out, what would I need to do in order to calculate the solubility product for calcium hydroxide?
  
  The following is what I have in mind, please tell if I am incorrect or correct.
  
  Ksp = [Ca+2][OH-1]2
  
  You should have an average value for the amount of H+ that you put into solution.
  
  For every 2 Mol of HCl added you neutralize one mol of CaOH2 right?
  
  Take the number of mol of hydroxide neutralized and divide by the volume of solution this will give you molarity of the CaOH2.
  
  You know from the stoichiometry that there is 2 times as much OH- present as calcium.
  
  So.. plug these numbers into the equation for the Ksp and you should arrive at your answer.
  
  Ksp = [molarity of OH- / 2 ][molarity of OH-]2
chemistry - DrBob222, Wednesday, April 2, 2008 at 12:47am
You must not have read the final volume for trial 5. Either that or you have misaligned the other readings.
- chemistry - Jessica, Wednesday, April 2, 2008 at 1:58pm
  When I have the table filled out, what would I need to do in order to calculate the solubility product for calcium hydroxide?
  
  The following is what I have in mind, please tell if I am incorrect or correct.
  
  Ksp = [Ca+2][OH-1]2
  
  You should have an average value for the amount of H+ that you put into solution.
  
  For every 2 Mol of HCl added you neutralize one mol of CaOH2 right?
  
  Take the number of mol of hydroxide neutralized and divide by the volume of solution this will give you molarity of the CaOH2.
  
  You know from the stoichiometry that there is 2 times as much OH- present as calcium.
  
  So.. plug these numbers into the equation for the Ksp and you should arrive at your answer.
  
  Ksp = [molarity of OH- / 2 ][molarity of OH-]2
- chemistry - Jessica, Wednesday, April 2, 2008 at 1:59pm
  When I have the table filled out, what would I need to do in order to calculate the solubility product for calcium hydroxide?
  
  The following is what I have in mind, please tell if I am incorrect or correct.
  
  Ksp = [Ca+2][OH-1]2
  
  You should have an average value for the amount of H+ that you put into solution.
  
  For every 2 Mol of HCl added you neutralize one mol of CaOH2 right?
  
  Take the number of mol of hydroxide neutralized and divide by the volume of solution this will give you molarity of the CaOH2.
  
  You know from the stoichiometry that there is 2 times as much OH- present as calcium.
  
  So.. plug these numbers into the equation for the Ksp and you should arrive at your answer.
  
  Ksp = [molarity of OH- / 2 ][molarity of OH-]2
chemistry - ~christina~, Wednesday, April 2, 2008 at 12:56am
I don't like to intrude but if I may make a comment on this.

I have to say that just like the previous trials didn't you record how much you added for trial 5?
(I'm not understanding how you don't know the volume you added for trial 5)
You CAN however, theoretically calculate about how much HCl you should have added to trial 5)
ycjarbw wnvgefaro - ycjarbw wnvgefaro, Thursday, February 5, 2009 at 3:15am
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