Pwyll Pendefig Dyfed

This is a little known example of Schroedingers Pinnochio. His nose both grows and doesn't grow at the same time.

I've always been a bit fascinated by hypothetical silicon based life forms. My chemistry background reminds me that they are not likely to exist anywhere because silicon has trouble forming catenated double bonds; but that doesn't keep me from entertaining the idea.

 

What's interesting to me is that any silicon based life from would necessarily have to have a water free biochemistry.

 

Someone wrote some science fiction on the topic but I can't seem to recall at the moment. If you can find it, I'm sure it is quite interesting/entertaining.

There was a Doctor Who sory I read once (I'm not sure if it was a TV episode or not) which had Silicon based Alien invaders.

My hangover cure is to drink water with a soluble vitamin C tablet in it, along with vitamin B complex.

If I'm drinking again the next day, then a pint as soon as possible after waking works well (although it seems to be frowned upon by the medical commuity). If I'm not drinking the next day a lie in in a dark room works.

You can convert not too complicated formated pdfs to mobi with calibre, btw.

You can also use calibre to convert RTF Word documnents to mobi format.

One of the problems I've seen with people saying that they're against cencorship is that it may lead to abuse of free speech. IMO making (for example) racist comments is not acceptable, even though the racist would claim free speech.

Shark certainly is not a relic of a dinosaur, it's a fish! Crocodiles a reptiles, which aren't descended from dinosaurs, and a Komodo (I believe) is a lizard, again not descended from dinosaurs.

 

With respect to geological formations, then I'd suggest that somewhere with lots of igneous rock is unlikely to have fissils as the lava would melt them! Sedimentary rocks would be more likely.

I've just realised I forgot the word not in that first sentence

Is it possible to edit post6s by the way?

I think crocodile, shark and also comodo was a living relict of dinosaur

Well.. i'm living in Indonesia, but there was no dinosaur fossils found in my area..is there any conditions in the past or geological formations that being dinosaur's places to live?

Shark certainly is not a relic of a dinosaur, it's a fish! Crocodiles a reptiles, which aren't descended from dinosaurs, and a Komodo (I believe) is a lizard, again not descended from dinosaurs.

With respect to geological formations, then I'd suggest that somewhere with lots of igneous rock is unlikely to have fissils as the lava would melt them! Sedimentary rocks would be more likely.

Which do you think has stronger attractions between their structural units: ions or molecules. Why?

 

There is the right answer, then there are stupid answers...

Molecules could exhibit Van der Waals forces, dipole-dipole attractions and hydrogen bonding between them.

Ions would exhibit electrostatic attraction between them.

Washing soda is added to hard water to allow soap to lather. A brand of washing soda contains partially hydrated sodium carbonate solid. A 0.300 g sample completely reacts with 20.0 mL of 0.250 M hydrochloric acid.

 

a) What mass of sodium carbonate was present?

 

b) Calculate the percentage by mass of sodium carbonate in the washing soda.

 

Please.

Any help would be appreciated!

How do I do this question? Would anyone be able to give me some hints/advice on how to tackle this question?

a) is a moles question. Calculate the number of moles of HCl, then using a balanced equation work out the moles of Na₂CO₃. Once you've got the moles, you can work out the mass.

b) use your answer to part a to answer part be as a percentage.

that's ok, but i'd just write: the indicator is used to tell when the solution is neutralized.

or: the indicator is used to tell when the sodium hydroxide has been completely neutralized.

Suppose now we have two acids

A. 10 cm3 of 1M sulphuric acid

B. 10 cm3 of 1M hydrochloric acid

 

I just want to ask how should I calculate in order to know which acid has a higher concentration of H+

Think about the definition of an acid, then the formulae of the two acids.

Most of the sugar in a potato is a glucose polymer known as starch. Is your question about the flavor of potatoes? I don't really see much other significance for the sucrose content of potatoes.

It could be an osmosis experiment, where the OP needs to calculate the concentration of the potato.

would atomic oxygen react with a water molecule, on contact, to give hydrogen peroxide?

(if i've got it wrong again i mean a single oxygen atom ion thingymajig, not combined with another oxygen atom)

At normal temperature and pressure it's going to go the other way:

H₂O₂ -> H₂O + O₂

The question is whether it is an equilibrium reaction, so can uthe equilibrium be shifted the other way by changing the temperature and/or pressure (using Le Chateliers principle)

When I take the last step for the slow step (as the rate law depends only on the slow step), I get something like

The first step (not the last step) is the slow, rate determining step.

Ok, yep I'm pretty sure I understand that now. Cheers

 

And so do u balance an ionic equation which contains unequal charges among the reactants and products, just like a normal (molecular) equation?

Do you have an example of the type of question you're referring to?

Ok, yep I'm pretty sure I understand that now. Cheers

 

And so do u balance an ionic equation which contains unequal charges among the reactants and products, just like a normal (molecular) equation?

Are you talking about an ionic half equation? If so the easiest way to do it would be to balance the electrons.

And is it the case in ionic reactions, that the closest matching ions within the formula of the reaction will come together, so therefore in a reaction the various ions won't just randomly react with whatever other ion..

I don't quite understand what you're asking here.

There is an electrostatic force attracting the positive ions to the negative ions. This force is similar to gravity in that the further away the ions are from each other, the smaller the attraction will become. The ions will attract those closest to each other.

Calculate the number of moles of each element.

I was wondering how you get the following: 2.00g H + 2.00g O2 = 1.75g H + 2.25g H2O...

 

and is it the case in ionic reactions, that the closest matching ions within the formula of the reaction will come together, so therefore in a reaction the various ions won't just randomly react with whatever other ion..

You need to look at it terms of moles.

Calculate the number of moles of Hydrogen, and the number of moles of oxygen (in 2g each).

You can then use the balanced equation to calculate how many moles of water could be formed.

Convert the number of moles back into mass, and you'll find your figures are true. 2.25g of water formed, and 1.75g of hydrogen left unreacted.

This question gets a lot of students.

 

The answer is quite counter intuitive, but there are several ways to analyze this. Hydrofluoric acid is a weak acid, unlike the other binary halo-acids. The "best" reason is the that the aqueous solvation shell that forms around a dissociated fluoride ion is highly organized; so much so that it creates a positive [math] \Delta S [/math] [change in entropy term] for the thermodynamics of the solubility equilibrium. Positive changes in entropy are not thermodynamically favored.

 

Also, HF in concentrated solution can begin to polymerize somewhat as a result of very strong hydrogen bonding interactions: [ce][HFHFHF]_{n}[/ce].

Ahhh, thanks.

Would that bit in bold be linked to the size of the fluoride ion?

Chlorine doesn't exhibit hydrogen bonding (even though it's very electronegative - more than Nitrogen IIRC which does exhibit H-bonding) but Fluorine does - kind of thing?

I recently saw a question about the difference between strong and weak acids. The question stated that hydrochloric acid is known as a strong acid as it dissociates completely, whereas a weak acid would reach a dissociated equilibrium (or words to that effect).

This is true for acids such as ethanoic acid of course, the question used hydrofluoric acid as an example. I was under the impression that Hydrofluoric acid is a strong acid, and the electronegativity of fluorine would mean that it would readily form the fluoride ion.

Is there a mistake in this question, or is there a reason why some could consider hydrofluoric acid a weak acid?

A far safer fireball is to light a splint, keeping it around 2cm off the floor (using a stand and clamp for example). Then sprinkle dried (fine) powdered milk onto it. The flame leaps up throught particles of dried milk, resulting in a fireball.

Ceribethlam,

 

For future reference, try not to simply give out answers to what are clearly homework questions.

Sorry. Is it possible to edit the reply?

Is the amu mass of an element reflected in molarity? I think 1 mole of a substance refers to a large but specific number of atoms, and thus the mass of this amount of a substance would reflect the exact mass of each atom. Now I'm wondering how you would count the required number of atoms to test the mass of a single mole of atoms.

Not molarity exactly, that's to calculate the number of moles in solution.

Number of moles = mass / Mr

1 mole contains 6 x 10^23 particles - Avogadros number. This is the equivalent to the number of atoms in 12 grams of the Carbon - 12 isotope.

Mass has units. The mass of H-1 is not 1, the mass of H-2 is not 2. Those are the mass numbers. The mass of H-1 is 1.0078250 atomic mass units (using C-12 as exactly 12), and the mass of H-2 is 2.0141018 amu.

Ah, get you, sorry, I misunderstood you

I meant atomic mass numbers, but wrote it as atomic mass (as oppose to mass number)