iodine diffusing to an area of higher concentration?
My biology class recently did an experiment in which we mixed 4ml of glucose and 4ml of starch in a bag made of dialysis tubing (a synthetic selectively permeable membrane), and submerged it in a beaker containing an iodine solution (200ml of distilled water mixed with 0.8ml of iodine), to see what size of molecules and ions that can pass through a selectively permeable membrane. Through lab execution and research, I found that the glucose molecules pass through the membrane into the beaker solution, and the iodine particles also passes through the membrane, to the bag solution. On the experiment sheet it says that the concentration of the bag solution is larger than the concentration of the beaker solution. This was where the confusion started. I began wondering why the iodine passed through the membrane, going from an area of lower concentration to higher concentration. How could the iodine ions diffuse through the membrane if this were the case? I tried researching online but no sources i visited mentioned the issue of particles from a lower concentration moving to an area of higher concentration. I found, however, that there is something called active transport, but that could not have occurred in this particular experiment as that process requires energy (from what I read), and dialysis tubing is non-living. Moments later I thought of a possible explanation, being that the water molecules in the iodine solution diffused through the membrane as there was no water located in the bag. This therefore caused the concentration of the beaker solution to further increase (as the glucose molecules entering the beaker solution already was increasing its concentration), so the iodine particles perhaps had to move through the membrane into the bag solution to balance out this large gain in concentration in the beaker solution. However, I am very unsure of this explanation. Can someone please explain why the iodine particles moved from an area of lower concentration to higher concentration if there is no evidence of active transport? I have an analysis due soon and I'm not very sure how to provide reasoning for the iodine particles "diffusing" to the bag solution. Thank you in advance. (Note that I am positive that the iodine ions were supposed to move through the membrane).
Free Energy Question
Hi,
Hydrogen peroxide can be prepared in several ways. One method is the reaction between hydrogen and oxygen, another method is the reaction between water and oxygen. Given the ?G°rxn values for each reaction, which method (reaction 1 or 2) requires less energy under standard conditions?
1. H2(gas) + O2(gas) <---> H2O2(liquid) ?G°rxn = -120.4 kJ
2. H2O(liquid) + 1/2 O2(gas) <---> H2O2(liquid) ?G°rxn = +116.7 kJ
Would the answer be reaction 2 because it is lower in magnitude? I know that a negative free energy value indicates a spontaneous reaction and a positive value a nonspontaneous reaction but is the sign significant in this case?
?G = ?G° + RTln(Q)
?G = -72.6 kJ + (0.008314 kJ mol- K-)(298 K)(ln 32.4)
?G = -72.6 + 8.6174 = -63.98 kJ
I am not sure about my approach to this question. Can anyone confirm if I am on the right track?
Thanks. All help Is very much appreciated.
dilute of HNO3
Hello guys
Please excused my english skills. I am from germany.
Currently I try to dilute or better create a 0,1 mol/l HNO3 acid. My parent substance is a 53% HNO3 whitout other data.
I need to run a electrolysis a 0,1 mol/l HNO3. Maybe my chemestry skills are very low, althougt I have a degree in a chemeststy similar profession. But I today I work in a other job, so that my chemestry skills fall day by day.
HNO3 = M = 63g/mol
W = 53%
But I have no idea how it goes on? Can anybody tell me, how I can fix this problem?
Precipitate with Si
Elemental silicon is oxidized by O2 to give a compound
which dissolves in molten Na2CO3. When this solution is
treated with aqueous hydrochloric acid, a precipitate
forms. What is the precipitate?
(A) SiH4 (B) SiCO3 (C) SiO2 (D) SiCl4
The answer is (C). I'm just very confused about what happens here. I thought that after elemental silicon is oxidized (the first step), SiO2 would be produced...but I have no idea if that's correct. I don't know what the reaction with HCl has to do with anything either. Could someone guide me through what happens after each reaction? Thanks in advance!
Conetration/Percent by mass
A solution is mad containing 22.8g of magnesium nitrate per 325g of water.
What is the weight/weight % or percent by mass of the solute?
I have tried twice to answer this and I don't seem to be getting it right. I know that for weight weight % you divide the two weights and then multiply by 100 to get the percent, but it's still incorrect.
Chemical Equilibrium: Position Shifts and Concentration Changes
Hi there,
My questions are in relation to the following system:
NaOH(s) <> Na (aq) + OH (aq) + energy
When NaCl (or just Na) is added:
i) Does the equilibrium shift to the left still despite the reactants being a solid?
ii) Does the concentration of OH reduce as a result of the equilibrium shifting to the left even though it isn't technically being consumed to form anything (as NaOH is solid)?
Thanks in advance.
Help Please! Redox Reactions!
Quickly wondering
What is oxidized and what is reduced as well as how many electrons are gained/lost by the elements in this redox reaction?
2H2 + O2 --> 2H2O + energy
Homework Help
I need help with a problem. it is due tonight at 10pm. please *delete me* I really don't know what to do.
How many grams of sucrose (C12H22O11) must be dissolved in 100 g water to make a solution in which the mole fraction of sucrose is 0.3?
Equilibrium and other calculations
Need help with two question please. If they can be done before 7 pm (CST) on March 1 2017...pleasee
1.What is the concentration of Fe3+ (after mixing but before reacting) in a solution made with 3.17 mL of 0.0621 M Fe(NO3)3 and 3.55 mL of 0.0235 M KSCN? Please include units in your answer.
2. A reaction mixture contains an initial concentration of 0.00617 M SCN- (after mixing, before reacting). At equilibrium, the concentration of FeSCN2+ is 0.00253 M. What is the equilibrium concentration of SCN-? Please include units in your answer. Please put your answer in decimal form.