Unasked Questions from 2009

-November 2009

• "Titration of acetylsalicylic acid"

I could have helped with that, I've already got sections on titration of monoprotic acids so maybe they found something useful here.

• "Assume that no heat is lost to the surroundings or to the coffee"

I would guess another calorimetry problem like the few I have solved here already.

• "How much faster do ammonia molecules effuse than carbon monoxide?"

Ahh, a problem that actually has enough information.  I actually already got this one here.

• "How to find the amount of NaCl in a sample of chips?"

Depends on how specific a person would want to be.  Covered a similar question previously but it was specifically worded to measure the amount of chloride ion.  Chloride can also be present as potassium chloride in some foodstuffs as well as present from other sources less frequently.  I would think that you would need to do some flame AAS to check for your sodium or some more exotic method and then compare to your sodium.

• "Hydrogen sulfide color"

Colorless, as a liquid, in solution, as a gas.  It's one of the reasons it's so dangerous.

• "Imagine that you have a 6.00 L gas tank and a 2.50 L gas tank."

Imagining... sorry, can't help beyond that.

• "Mercury and nitric acid"

Depends on the temperature and concentration of the acid.  Concentrated acid and heating will afford mercuric nitrate, more dilute acid and less aggressive heating will give the +1 nitrate.

• "Helium-oxygen mixtures are used by divers to avoid the bends"

Statement of fact, wonder why that lead to my site?

 

-October 2009

• "Bubbling ammonia into a solution of bromic acid will produce what?"

  Ammonium bromate, just an acid/base reaction.  The real question is what happens when you try to evaporate this solution to isolate your ammonium bromate?  If you know anything about ammonium chlorate you can guess what the answer is.  Boom!  Some bromates are more stable than the chlorate counterparts (I could be wrong, I know that perbromates are higher oxidation potentials but are more kinetically slow).

-September 2009

• "Why lead bromine is insoluble in water"

  The easy answer for me is that the dissolution is not thermodynamically favorable.  That the crystal structure is very stable, there is no energy gain in dissolving.  Good overlap between the orbital and all that jazz.  Honestly without looking it up I cannot properly defend my answer.  I know that cations such as lead that don't coordinate well with water can be dragged into solution so to speak by an appropriately hydrophilic anion such as nitrate or triflate.

  
  

• "A red highly reactive fuming liquid with a foul smell"

  A number of these liquids are colored due to impurities but:  Chromyl chloride, sulfonyl chloride, thionyl chloride, sulfur dichloride, disulfur dichloride, and bromine all fit the bill off the top of my head.

• "Distilling sulfuric acid"

  You distill it just like any other compound, you just have to really kick in the joules to get it coming over and also it is known for bumping in the historical literature and in practice.  It's a pretty scary affair in improvised glassware.

-August 2009

• "Activation energy of potassium permanganate experiment"

  I'm at a loss...

-July 2009

• "lead in nitric acid"

  The amount of lead in nitric acid depends on the grade.  There is a trace metal grade available along with others that will have a bare minimum of lead.  If you are asking of adding lead to nitric acid it will form lead (II) nitrate, lead (IV) nitrate is going to be out of reach in aqueous conditions.

• "neutralize acetone"

  Fire?  Not really sure what the question was but it was a funny thing to search.  Acetone is actually consumed by a number of microorganisms in the waste water treatment process.

• "Basic solution store glassware silica reaction"

  Strong bases with react with glass over time to give silicates and also borates to some extent.  The reaction is usually slow but it does occur.  I've had occasion to melt sodium hydroxide in glassware where the speed of the reaction is in the visible range (scary!).  My old chemistry book warned against storing cesium hydroxide in glassware due to dissolving glass, I have to wonder how much faster the cesium hydroxide does its magic than the standard sodium hydroxide reagents for which I see glass bottles around from time to time. 

  2OH^- + SiO₂ ---> SiO₃^(2-) + H₂O

-June 2009

• "Carbon disulfide gas color"

  Colorless, this doesn't suddenly become chromophoric in the gas phase.

• "Add Cu coil into a test tube containing AgNO3 solution. what will happen?"

  You make a silver tree.  the silver will precipitate out by growing onto the copper wire and the copper will go into solution to replace the silver.

-May 2009

• "reaction of sodium hydroxide on urea"

  One of the steps for the synthesis of hydrazine from urea is to add in a quantity of sodium hydroxide.  This is to neutralize acid as the reaction progresses / free up the hydrazine.  Looking at it from a mechanistic point of view, in the aqueous phase you've got your hydroxide which is going to be a neucleophile and you've got your electrophillic carbon.  If they meet head on you end up with your tetrahedral intermediate... then what?  You are not going to split off amide (NH₂^-) you're going to spit off your hydroxide and go back to what you started with.  At higher temperatures and non-aqueous conditions however urea can react with various hydroxides to give carbamates which can go further to give cyanates.

-April 2009

• "Preparation of benzoic acid excess HCl"

  My guess is that the person asking the question wanted to make benzoic acid.  They dissolved sodium benzoate in water and they were wondering how much HCl to add in excess to precipitate out all their benzoic acid.  More acid than theoretical will force it out due to common ion effect but benzoic acid itself is not very soluble so you're not going to eek out much more.  Or perhaps they had precipitate out all of their benzoic acid and they were having problems with too much HCl in their product.  Drying under vacuum or with gentle heating could help remove this.  I would recommend against washing with base although another water wash might help.

-March 2009

• "Alcohol acetone and potassium hydroxide reaction"

  This reaction can be used to produce a hemiketal or ketal but it can vary also depending on the properties of the alcohol used.

• "Electrolysis of aqueous lithium chloride"

  Lithium hydroxide and chlorine gas if a proper membrane is present.  Lithium hypochlorite if temps are cool and mixing, chlorate will be present if temp of solution is allowed to rise.

• "Experiment of iron chloride and sodium hydroxide"

  In most instances this will give you iron hydroxide and sodium chloride.

• "Preparation of nickel oxalate"  "preparation of urea oxalate"

  During my experiments I simply used a slight (5%) excess of oxalic acid per calculations on my nickel chloride solutions.  I found out later that heating nickel oxalate usually gives nickel oxide however and not free nickel.

• "Reaction of lead sulphide with nitric acid"

  Although lead sulfide is not soluble (most sulfides are not) it will react with acids to give hydrogen sulfide and the appropriate lead salt, in this case lead nitrate.  Since lead nitrate is soluble it will allow the reaction to keep going and going and going.

-February 2009

• "Bromic acid with NaOH"

  Sodium Bromate and Water

-January 2009

• "Does liquid nitrogen smell like ether?"

  Not normally.  It just smells like cold.  I think even if you spilt ether in it you wouldn't smell it because at those temperatures the vapor pressure is closing in on zero.  Back when I used to use liquid nitrogen around my pump traps I could never smell the contents of my traps when dumping them due to how cold things were.