Need Help with Chemistry

[Harkdawg]

guys im a little lost here ::), im gonna take a chem test in June (dunno what to call it exactly in english, but you need certain tests to apply university) anyways i decided to make Chemistry as one of them.

Well anyways, im going through 8-9th Grade chemistry atm and im reading the books. Everything seems very easy and simple, however there is something i do not get. Also the damn book is a short course of 8-9th grade chemistry and it doesnt cover Balancing Equations. It just says in certain exercises that write down the result and balance the equation. As i mentioned, the book itself has no chapter about balancing, it just wants me to do it. Now i do remember mostly how its done from my school years, but i couldnt figure this out

P4O10 + H20 -> H3PO4  now theres 11O on the left side and 4O on the right, now to me, the first multiplier those two meet the requirements for is 44, so that means i have to write 4P4O10 + 4H20 -> 11H3PO4 that would get me right amount of O , but at the same time look at P > left side =16P while right side = 11P and aswell the H, left side H=8 right side H=33

so this wut i couldnt figure out

i did find a little instruction on equation balancing on the web, eventhogh its in English but i understand it.

There is a particular order that you can follow in balancing. It is the MINOH method

(Me know chemistry, said Tarzan as he climbed the stoichiome-tree.)

M - metals. Balance metals such as Fe or Na first.

I - ions. Looks for polyatomic ions (such as PO4

[gunner154]

The answer is P4O10 + 6H20 --> 4H3PO4

If I'm not wrong, the correct equation should lead to H3PO3 first, since you don't get phosphoric acid first but rather phosphorous acid first. My Chemistry is a bit rusty now, but I think that's what it should be.

Good luck with your Chemistry test ;)

Edit: I don't follow any strange guidelines or anything to help me balance equations. I normally rely on trial and error. The only format I need to use when dealing with equations is knowing how to construct balanced ionic equations from their half equations.. but that's another matter.

[Harkdawg]

thnx gunner, that seems simple, how i missed that  :P

also, i dont understand many chemical terms in English ... so alot what u guys say might seem jibberish at first sight but ill try to adapt :)

[gunner154]

You're welcome. I just edited my post - I just rely on trial and error. Of course, the first thing that crossed my mind was to deal with the P first, but after that I decided to deal with the O and magically the H was dealt with too. So perhaps I'm following your format subconsciously. ;)

Oh, and balancing equations properly requires some practice. If you're new to balancing equations, start off with balancing simple ones like neutralisation reactions or the dissolution of metals in acid, and then move on to deal with relatively stranger chemicals like those involving phosphoric acid, etc. After some practice you should be proficient enough to deal with most equations at your level :)

[Harkdawg]

Well while im at i might aswell ask one more thing about Electric Schemes (if thats what they are called in english) ill write something down:

Element Ti

Ti:+22|2)8)9)2)

Those who know how its done then explain me this:

As the rule says-

period number is number of electrical layers

on Ti thats 4

The serialnumber is the number of Electrons in the whole Electron cover

on Ti thats 22

The last layers electorns number = groups number

Ti is from IVB group so B groups oughta have usually 2 electrons in the last layer so i fill the last layer first with 2

and the rest of the layers will fill as follows 2/8/18/32 etc while remembering that last layer can hold maximum of 8 and the one befor that 18

so with Ti + 22| 2)8 ) after filling two layers i calculate the next with 22= 2+8+?+2 ? = 9)2)

ok it works perfect with most of the elements, Exactly most of the elements and the book doesnt say anything about exceptions, but heres what i tryed

Do the same thing with Ba,La,Cs or any of the 7th period Elements and it wont work

Ba: +56|2)8)18)32) ? )2) So you see, at the 5th layer already the amount Electrones is used, by the end of the 4th layer there is 62 electrones used eventhough 56 is maximum and theres 6 layers to fill 

[gunner154]

The problem is that things are not as simple. I don't think it is necessary to go into the details exactly, since understanding how exactly filling up electron "shells" works for elements of a higher period work because that means you need to do the Orbital theory, which I'm not sure if it's in your syllabus (I don't know what 8th and 9th grade stand for, or their equivalent in Singapore).

To begin with, I don't really understand what you're talking about, especially the 2/8/16/32 part, because according to the orbital theory, it should be 2/8/18/32 (for each shell), in a grossly simplified manner.

However, supposing that whatever you mentioned is correct, you should notice that in Period 7 and 8, the standard periodic table is intruded by additional Lanthanides and Actinides respectively, so that might obstruct your prediction altogether.

Prediction of the electronic structure of those elements is still possible, going by first principle in the orbital theory, but as mentioned earlier in the post it might be a little complicated since there are some details to explain. But I can explain it nonetheless, but another day.

Oh, and if I'm not wrong, the proper term for it is Electronic Structure, not Electronic Schemes. At least Structure is more familiar to me than Schemes.

Edit: You can see the 2 other parts of the Periodic Table here: http://en.wikipedia.org/wiki/Periodic_table

Note that the relative atomic number actually continues into the additional part before going back to the main table.

[Harkdawg]

Yes the test includes the Oribitals(s,p,d,f), the hybridisation of orbitals, the filling of them , sigma and pii connections And a whole lot of other stuff.

Im just going through 8-9th grade material first to remember everything correctly to follow up with high school material. I graduated high school 2 years ago, was in the army last year, and now im just studing to take the tests and go to unviersity.

I guess i havent just read that far yet

oh and when i was in high school i just didnt care much about learning anything. I didnt care, i wish i wouldve been smarter at 15 :) but atleast i came to my sences at 20 :)

Gunner 2/8/18/32 that 16 was typ and i fixed it

And to my original question, i knbow what i did wrong. it said in the book something in the lines of PO4

SO3

SO4

(dunno the term in english)

that balance them as whole so i thought PO4 as (PO)4 meaning i thought that in the equation there was also 4 P atoms :P silly billy while there was just 1 and 4 O atoms.

And i also know what the book ment by balancing them as whole, it ment if i put a number infront of "them" (PO4 etc.) that it will acceft both rather thatn try to balance trhem alone

Meaning -

2P04 = 2P atoms and 8O Atoms / not 2P3O4 , this what the book ment.

[Timenn]

What I can tell you about the layers of electrons is that you won't learn at school the precise formula to determine the probability positions of electrons. That's academic stuff for physics. (Very long calculations, massive integrals)

Any formula you might learn is a rule of thumb, and therefore there can be exceptions which don't apply to the rule of thumb.

[Harkdawg]

put the books could point it out. under a paragraph mention that things are more complicated and there are exceptions.

[gunner154]

In fact, I don't remember encountering any formulae for calculating the probability.

Good that you understood what balancing equations mean actually :)

PO4 - Phosphate ion

SO4 - Sulphate ion

SO3 - Sulphite ion

[Harkdawg]

Well ive been reintroduced to most of the basics by now.

Ive been completing diffrent reactions and balancing them. Reactions between diffrent compounds(salts,acids,oxsides, metals etc. ) But umm i was a little confused about the following, the simplest of the simplest.

Any reaction with metals requires the (dunno if i say it right= oxydation level , like Al +3 , Fe +2 or +3 O(-2) in compounds )

so as a result ill take some really simple Oxside forumals like

2Mg + O2 = 2MgO (Mg being +2 and O being -2 ) or umm

4Al + 3O2 = 2Al2O3

4Li + O2 = 2Li2O

So as you see its rather simple with Metals, however with Non Metals, how do i determine the indexes ?

For example is

C + O2 = CO2 ?

N2 + O2 = N2O2 ?

P + O2 = PO2 ?

S+ O2 = SO2 ?

Do i just add em up ?

This was the excerise, finish the formulas and balance them. I could finish the Metal + Oxgyen, however nothing is mentioned about non metal oxides and now it wants me to finish them.

[gunner154]

It's oxidation state, not oxidation level :)

Actually, for non-metals, to be very frank, oxidation state of the non-metal is required too. For example,

C + O2 --> CO2, right? That's just combustion of carbon.

But you can also get carbon monoxide, which is CO.

So 2C + O2 --> 2CO

Nitrogen is another tricky problem. There are VARIOUS nitrogen oxides present, like N2O4, NO, NO2, N2O... so you really need to know what your end product should be.

Therefore, like metals, you need to know the oxidation state as well. By right, you should be given the reactants as well as the products, so that you can construct the balanced equation.

[Davidu]

OFF TOPIC:

Oh GOD I haven't seen chemistry since high-school.

I see Gunner is quite good at it.

You know sometimes I have the urge to go and take up some math or chemistry problems, just to remember those days. I miss high-school, you know?

[gunner154]

I'm still studying it, mind you :P I would be damned if I've forgotten everything after 2 months of holidays.

[Harkdawg]

ok now i just went through the basics of Organic Chemistry. Now, again i feel this shourt course book fails to explain to me many things.

As i was writeing this message and looking at the book at the same time i think i just figured out my questions answer, so im just gonna post what the exercize was and you can tell me if i did correctly.

apologizeing for the spelling, dunno the correct terms in english so im translateing them directly

To sumformula (molecularformula) of C3H60 equals two diffrent substances. Create their Structuralformulas.

heres what i thought would be correct, but is it ?

NOTE !!! the top right thing went bad and bottom left went bad. The top left and bottom right are the right ones, just them, is this correct according to the execrize?

NOTE !!! replaced the word equation with formula, i think its more correct.

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[Harkdawg]

Oo Gunner, were art thou ?  ::)

ok i got another problem its about dilutioncurves (spelling ?)

The book mentiones what it is shows an example and then moves on, and afterwards, in exercizes, wants me to read stuff out of it that it failed to explain me how to do !!!

ill post the exercize so if you know how to do it, could you please explain step by step how its done so id understand.

Using sugars Dilutioncurve, find out, how many grams of sugar crystallizes, if 200g of palled  Sugarsolution at 80 degrees Celsius is cooled down to 15 degrees Celsius.

Now the answer is 70g, its written behind the exercize but it fails to explain how do i read it out of the curve, im lost here !

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[Phoenix]

Offtopic:

Things like calciumcarbide with water.. --> will result in acythyleen gas highly flamable and under pressure explosive :D

or I2 cristals with HCl --> dont try at home, its higly instable when dry :D

maybe with H2O2 with some thing ;)

are funny.

And as chemistry in school: I have once, a long time ago, done some searching to the burning speeds of several blackpowder compositions in school :D it was funny :D

But as long as it is sugar and dilutioncurves, it sounds good to me but when ppl gonna talk about H2 gas with O2 gas mixed in something big, and then try to lit it.. its starting to sound like terrorists to me.. :D

[Phoenix]

ok ontopic..

Using sugars Dilutioncurve, find out, how many grams of sugar crystallizes, if 200g of palled  Sugarsolution at 80 degrees Celsius is cooled down to 15 degrees Celsius.

Now the answer is 70g, its written behind the exercize but it fails to explain how do i read it out of the curve, im lost here !

In my opinion. If you see the curve you posted.

@ 80 degree celsius, there disolves 360 gram of sugar in water.

@ 15 degree celcius, there disolves 200 gram of sugar in water.

This makes 160 grams of sugar wich will cristalize during cooldown. (in 100 gram of water..)

[Harkdawg]

yes taht would be correct, BUT thats not what the exercize wants. There is 200 g of sugarsolution not 450 g (350 g of sugar wich is maximum wich solves in 100g of water at 80 degrees). So there is just 200 g of solution not 450 at 80 degrees, thats why it has to be done a little diffrent.

[Phoenix]

ah i see..

that would make it 71,1111 grams

so that is 450g / 200g = 2,25

160 grams of cristalized suger / 2,25 --> makes 71.1 :D

Hoaah! :D im still good in chemistry :D

[Harkdawg]

that might be correct , if only gunner could confirm it, id be happy.

[Phoenix]

well if gunner would read this, he would confirm it ;)

[gunner154]

Sorry for the late reply. I don't use the computer when I'm having school, until it's the weekends. And it's a Friday. Nevermind.

As far as the organic chemistry question is concerned, yes. The top left and bottom right are correct. This question is simply dealing with isomerism, and basically there are several arrangements of the bonded atoms to form various compounds. Some of them have similar chemical properties and some don't. It depends on the structure.

And for such topics, to figure out ALL the combinations, you need a computer to do it, especially for larger compounds. And most of the time, if you can actually draw out the structure, fulfilling all the bond rules and fulfilling the collapsed formula you have provided, it's probably correct. But here's an idea I thought of: Use double bonds.

H H H

| | |

H-C=C-C-OH

   |

      H

H H H

| | |

C=C-C-H

|   |

OH  H

As for the solubility question, I have never encountered dilution curves before, and only solubility curves, and even those aren't really covered in the syllabus. But I'll see what I can do.

The X-axis of the graph is quite straightforward. It's just the temperature. The Y-axis is the problem.

I GUESS it refers to the mass of sugar that dissolves in 100g of water at that temperature.

I agree with Phoenix's first analysis. It's about as correct as I'd thought, but since that only refers to the dissolving of sugar for every 100g of solution, you just multiply the result by 2 for 200g, since I suppose it's asking about the absolute mass of sugar that crystallises.

About 200g will dissolve at 15 degrees celsius in 100g (or 100cm3 of water, since density of water is 1g/cm3). About 360g dissolves at 80 degrees celsius in 100g of water. So how much crystallises? 160g of sugar. However, since we're talking about 200g of solution, that means you double all the quantities. Thus, 320g crystallises.

However, something baffles me. Phoenix used 450g/200g=2.25. Why do you use this?

The second step is equally baffling. Perhaps you would like to explain your solution? In fact, I find it erroneous that 450g is even considered. What does 200g of solution stand for? 200g of water? Or 200g of sugar+water? It's not correct to consider the maximum mass that dissolves and assume it to be the mass of the sugar dissolved, because temperatures can be higher, so what's the max? And besides, the question didn't say that's the mass dissolved. You need to know the volume of water in the solution in order to use the graph, and if you don't have the total mass of sugar in the solution, you cannot find out how much water is used, and thus you can't solve the question. Thus, I assume that 200g of solution refers to 200ml solution, and since density of water is 1g/cm3, the volume of the solution is 200ml. That makes more sense.

[gunner154]

yes taht would be correct, BUT thats not what the exercize wants. There is 200 g of sugarsolution not 450 g (350 g of sugar wich is maximum wich solves in 100g of water at 80 degrees). So there is just 200 g of solution not 450 at 80 degrees, thats why it has to be done a little diffrent.

And on a side note, the initial analysis made by Phoenix assumes that there is 200g or 200ml of sugar solution, and had nothing to do with 450g.

This site covers the basics of solubility curves: http://www.thesciencedesk.com/sgsolubilitygraph.htm

[exatreide]

eww chemistry.. Have a test over Moles today.. that I will probebly fail..yea.