Conductivity

[drowningfish134]

hey im doin a chemistry assignment and i cant figure out how to do the following things

Account for the difference in the conductivity of

1.)sucrose solution and silver nitrate solution


2.) solid silver nitrate and solid sodium metal


3.) liquid (fused) sucrose and liquid(fused)silver nitrate

please help

[cristo]

Hi, and welcome to PF! Please note that our rules on homework help state that we cannot give out solutions before you have shown us your effort. Please post your thoughts on the question. Also, in future, please post in the other sciences section of the homework forum!

[drowningfish134]

sorry i well do so

[drowningfish134]

well for the first one i was thinking the difference would be because sucrose solution is molecular and insolube in water the conductivity is really low, and the conductivity of the silver nitrate in solution is very good because it is ionic and ionic bonded compounds generally have better conductivity? am i right? and if not whats wrong?

[drowningfish134]

for the second one, the AgNO3 would not conduct because of an ionic compound in the solid state, and the sodium metal conducts well because if not all most mettcalic compound always conduct.

[drowningfish134]

for the third one the ligquid solution of AgNO3 would be just as good as the solution of AgNO3 but i do not have ne ideas on the liquid silver nitrate

[cristo]

well for the first one i was thinking the difference would be because sucrose solution is molecular and insolube in water
Sucrose is soluble in water

the conductivity is really low, and the conductivity of the silver nitrate in solution is very good because it is ionic and ionic bonded compounds generally have better conductivity?
This is correct. Do you know why ionic solutions are more conductive?

[cristo]

for the second one, the AgNO3 would not conduct because of an ionic compound in the solid state, and the sodium metal conducts well because if not all most mettcalic compound always conduct.

Correct. Do you know which specific properties of metals enable them to be good conductors?

[drowningfish134]

because the ions are free to move around in the water

[drowningfish134]

becuase in the a metal the electrons are not attcher to any particular cation and so theres a larger amount of mobile electrons?

[cristo]

for the third one the ligquid solution of AgNO3 would be just as good as the solution of AgNO3 but i do not have ne ideas on the liquid silver nitrate

Read what you've put here again. I think the last bit should read but i do not have any ideas on the liquid sucrose.

You're right with the AgNO3; the fused ions move and therefore the liquid conducts. For the sucrose, what has changed? Is the liquid sucrose molecular or ionic?

[drowningfish134]

nothing has changed, its still molecular, so it still doesnt conduct

[cristo]

because the ions are free to move around in the water Well, the ions are free to move around in the solution.

becuase in the a metal the electrons are not attcher to any particular cation and so theres a larger amount of mobile electrons?

Correct. Metallic bonding is usually described as having a "sea of free electrons" enabling the metal to conduct.

nothing has changed, its still molecular, so it still doesnt conduct

Correct

[drowningfish134]

im sorry to keep asking questions but i am strugglin in this class...

i have to draw the cooling curves of both a pure solvent and solution.
which one is correct


PS
-
-
-
- ---------
- -
--

solution

-
-
- -----------
- -
--


or

PS
-
-
-
-
-----------
-
-
-
and solution is the same but the flat line has a slight negative slope??

[drowningfish134]

that didnt work....is it this http://home.att.net/~v.d.singleton/genchem/curve.gif
which i think is right or is it go down than parabolas back up then flattens out at the freezin point

[cristo]

that didnt work....is it this http://home.att.net/~v.d.singleton/genchem/curve.gif
which i think is right or is it go down than parabolas back up then flattens out at the freezin point

Strictly, as you say, a pure solution would undergo a stage of "supercooling" in which the temperature drops below the freezing point, and then parabolically increases back to the freezing point, and levels out.

Other than that, the graphs look fine.

[drowningfish134]

so is ut rge pciture on the website or the wordsi wrote

[cristo]

You can add the parabolic part onto the graph on the website, so in answer to your question... both!

It really depends how advanced your class is, but since you mentioned the "supercooling" then you should draw it on.

[drowningfish134]

alright thanks a bunch!!

[cristo]

alright thanks a bunch!!
You're very welcome!

[drowningfish134]

all right, im glad i found someone can help me!

Concentrated sulfuric acid (18.4 molar) has a density of 11.84 g per ml
dilution with water to 5.20 molar, density of 1.38 g per ml
can be used as an a electroyte is lead batterys.

What is the molality of the 5.20 molar H2SO4 solution?

well im not exactly sure where to start, but i know that i need to find moles of solute/kg of solvent. i think i should start with grams in one liter and use that to find the number of grams or moles of solution, but other than that i am pretty lost.

where am i wrong and whats next?

[cristo]

It's a long time since I've studied any chemistry, and so I'm rather rusty on calculations. I think it's best if I leave this one for someone else to help you with!

[drowningfish134]

should i repost witha new topic name?

[cristo]

Well, I guess you already have! Here's the link to the question, for anyone that's reading through this thread: Molarity (http://www.physicsforums.com/showthread.php?t=151231)