Question

Solution Concentration and Conductivity.
Any help would be greatly appreciated.



To 30 mL of the Ba(OH)2 solution, 10 mL portions of H2SO4 were added until a total of 50 mL of H2SO4 were used. The following results were recorded.

DATA TABLE
Total H2SO4 Added Meter Reading Observations
0 mL 150 mA Ba(OH)2 and H2SO4 clear, colorless
10 mL 65 mA milky white precipitate forms
20 mL 31 mA more precipitate forms
30 mL 0 mA precipitate heavy and settles
40 mL 29 mA no added precipitate seen to form
50 mL 62 mA no change seen

Answer 1

Does the number of ions in solution increase, decrease, or remain constant?

Answer 2

What is the indicator of the number of ions in solution?

Answer 3

How does this evidence indicate that the reaction has occurred between ions?

Answer 4

If it helps, here is a cruddy graph.

Answer 5

Does the number of ions in solution increase, decrease, or remain constant?
fist decrease until 30ml then increase again

What is the indicator of the number of ions in solution?
the conductivity = mA

How does this evidence indicate that the reaction has occurred between ions?
by adding H2SO4 to Ba(OH)2 you are producing BaSO4, a mostly insoluble compound. as you increase the volume, and thereby the concentration of SO4-2 ions, you will see a precipitate form. this means that the [Ba+2] will decrease, the [H+] will increase with each addition of H2SO4, the [OH-] will react with the [H+] making H2O the same and the [SO4-2] will decrease becose react with the [Ba+2]. The more precipitate formed, the fewer Ba+2 and SO4-2 ions will be in solution and the fewer [H+] and [OH-] until the current is near 0 mA, then you will have excess of SO4-2 and H+ the number of ions increase again increasing the conductivity

Answer 6

I have a few more questions, if that is alright.
Does the conductivity increase or decrease? Is this the same as the number of ions? Decrease then increase?

The Ba(OH)2 dissociates as Ba+2 + 2 OH-. H2SO4 dissociates as 2 H+ + SO4 -2.

Write a balanced equation for this reaction.

When the conductivity is at a minimum, what must be true about the amount of Ba(OH)2?
There is a lesser amount of Ba(OH)2?

Why does it not conduct at this low point?
Too much of H2SO4?
Why does it conduct more before and after this minimum point?
A proper chemical balance is reached?

Answer 7

I have a few more questions, if that is alright.
Does the conductivity increase or decrease? Is this the same as the number of ions? Decrease then increase?
YES

The Ba(OH)2 dissociates as Ba+2 + 2 OH-. H2SO4 dissociates as 2 H+ + SO4 -2.
H2SO4 has two step dissociation
H2SO4 -> H1SO4- + H+ --> SO4 -2 + 2 H+


Write a balanced equation for this reaction.

Ba(OH)2 + H2SO4 --> BaSO4 + 2H2O

When the conductivity is at a minimum, what must be true about the amount of Ba(OH)2?
There is a lesser amount of Ba(OH)2? Yes

Why does it not conduct at this low point?
Too much of H2SO4? no enough ions in solution

Why does it conduct more before and after this minimum point?
because are more ions in solution before and after the equivalent point

A proper chemical balance is reached?
(???)
I dont understand what is this asking about chemical balance? a balance to weight chemicals or balancing a chemical equation? neither is reached.
If they are talking an equilibrium...always can be an equilibrium at any point of the reaction

At the lowest conductivity point you have the equivalence point when the two ions are in stoichiometric proportion