In pursuit of understanding

[kenneo]

First off I would like to say that I hold this forum and its members in the highest regard. I have read some of the most creative and truly ingenious ideas thought of on this site and aspire to attain the knowledge and understanding of chemistry that many of you here possess.

Being an electrician, and having studied numerous volumes on electromagnetic theorem, I am familiar with atomic structures and the presumed forces at work therein.

But my weakness lies not in theory, but rather understanding of the basic rules that govern chemical reactions in equations.

Most of the information I've researched first starts with the Law of Conservation explanation, then a chemical reaction (example:) Tin oxide is heated with hydrogen gas to form tin metal and water vapor. Write the balanced equation that describes this reaction.

Write the unbalanced equation.
SnO2 + H2 --> Sn + H2O

then immediately goes into balancing the equation, but how did they arrive at the unbalanced equation? How does SnO2 + H2 form Sn + H2O? what steps were taken to conclude this in the equation form? I'm sure it's not as easy as 1+1=2 but there must be a formula or set of rules to help you determine this.

If anybody knows of a website that details this process, or can offer an explanation I would surely appreciate the heads up.
Thank You.

[megalomania]

In a nutshell it all boils down to electonegativity. You are an electrician, so you should understand the concept that chemical reactions involve the flow of electrons from one atom to another. The electronegativity of every element on the periodic table has been experimentally determined. In general electronegativity increases from the bottom up, and from the left to right. Fluorine is the most electronegative element.

Now how does electronegativity help you predict a chemical reaction? For organic reactions it does not help much, and most of the time everything has to be experimentally determined anyway. In theory electrons will flow from a less electronegative element to a more electronegative element.

2Na + Cl2 --> 2NaCl

Sodium burns in a chlorine atmosphere. Chlorine is a very electronegative element, it wants electrons. Sodium has too many electrons in its opinion, so it is happy to give them up. Why does sodium want to get rid of its electrons and chlorine want more? That has to do with the octet rule, or the rule of 8 which has to do with stable electron orbitals.

SnO2 + H2 --> Sn + H2O

Hydrogen is acting as a reducing with tin in this reaction. It is easier for oxygen to share the electrons from hydrogen because hydrogen is more electropositive than tin. In laymens terms the hydrogen atoms are far more willing to give up their electrons than the tin is. The resulting molecule of tin and water is more stable than tin oxide and hydrogen. The balanced reaction should be SnO2 + 2H2 --> Sn + 2H2O

In short there is no simple answer to a question like yours because there is a TON of chemistry behind it. There are things that you must simply know. Acids react with bases to form salts, things get oxidized or reduced, there are strong oxidizers, and strong reducers. Some substances may result in a precipitation that removes that ion from the solution. Electrolysis can reverse reactions. Under the right conditions just about any element can be made to react in a way it would not ordinarily.

The reason an unbalanced reaction is used is for simplicities sake. It really does not matter that there are two moles of hydrogen for each mole of tin oxide. All you really need to know is that tin oxide reacts with hydrogen to form tin and water, and that is what the unbalanced reaction conveys. If you were actually making tin metal by passing hydrogen gas through a tube filled with heated tin oxide, the balanced equation would be largly irrelevant since all we care about is the end product, tin. We still need to pass an excess of hydrogen over the oxide, but that is something learned only through experimentation and real world experience. Only homework problems make use of perfect stoichiometry.

[kenneo]

Mega, I appreciate your response. Electronegativity is an aspect of THEORY of which hadn't clicked to me before in trying to understand chemical reactions, but which is starting to make sense now on a lower level(I Think).

Having researched it a little, it seems to me that Electronegativity would equate to something like GRAVITY on a macroscopic scale i.e. the sun is more Electronegative than the earth and so on... for whatever reason I guess:rolleyes:

I know I have a TON of material to learn.

The confusing part for me is the result from the reaction, for example you said 2Na + Cl2 ---> 2 NaCl. What steps did you take to figure that out? Do you through experience automatically know that somehow? In 2Na + Cl2 combined (reacted) to make 2 NaCl, what happened to the 2 after the Cl? I'm missing a step somewhere (maybe several) and I'm unable to see where it is. Again I appreciate your time in helping me with this matter.

[FUTI]

Mega I wouldn't try to explain to anyone something like this in terms of electronegativity. Your aproach is OK since he choose a reaction with gas hydrogen. Affinity toward electron and ionisation potential are two REAL parameters that can describe reaction involving gas phase (although this is solid-gas mixture but anyway...). This two values are sometimes used to define electronegativity.

Now there is a problem...I once counted diferent ways of defining electronegativity and give up after I reach method number 7. Electronegativity is little arbitrary value. True value indeed, but obtained with little adjusting the theory/table data to fit the observed experimental data.

kenneo, Mega is right. None can teach you chemistry during a chat session. You could look for a table of redox potential in some chemistry book. I think it would make your life easier since it is closer to your field of work. Don't take this as fool-proof method of understanding how chemical reaction can be writen, as Mega said there is a still a ton of chemistry for you to learn, but for a start this should work.

[megalomania]

Chlorine exists in nature as a diatomic molecule, Cl2. Sodium exists only as Na in its metallic state. The reaction then involves Cl2 + Na, but because we have two chlorines we have to add a second sodium to balance the reaction. Two atoms of each element going in give us two molecules of NaCl going out. That chlorine is diatomic is just one of those things you must know from reading chemistry texts.

[kenneo]

Thanks for the replies guys, It appears as though I've jumped the gun on the whole reactions thing. After some serious pondering and some reading, I've now realised what Mega was talking about when he said:

In short there is no simple answer to a question like yours because there is a TON of chemistry behind it. There are things that you must simply know. Acids react with bases to form salts, things get oxidized or reduced, there are strong oxidizers, and strong reducers. Some substances may result in a precipitation that removes that ion from the solution. Electrolysis can reverse reactions. Under the right conditions just about any element can be made to react in a way it would not ordinarily.


I apologize for posting this in the first place. I should have figured this out on my own. I thought there was possibly a "shortcut" or simple set of rules to determine results of reactions, but I now see that there are alot of variables involved, Of course, anything of value is never attained easily. So I have ALOT of reading to do. Thanks again.

[GibbsFreeEnergy]

An understanding of the concept of concentration in chemistry might be necessary to help you really understand a chemical equation. The standard units for chemical equations are called "mols" which are a unit of measure that indicates a standard amount of atoms, which happens to be 6.02e23 atoms. This number of atoms equals one mole. One mole of any element is equal to the weight given on the periodic table (unless that element is diatomic; an element that only naturally exists in "pairs" because of the stability of a bond between two units of the diatomic element). One mole of any molecule is equal to the weight of all the elements making it up. For example, if one had 10 grams of NaCl (Table salt) they would have 10.0 g/58.5 grams per mole (from peroidic table) which gives .171 moles of NaCl. When one refers to a compound that is not primarily made of ionic bonding, this total weight is referred to as molecular weight. If the compound in question has ionic bonding primarily, it is referred to as formula weight. Concentration in chemistry is measured in different units. Many of these units use mols per some volume to determine a concentration. It's like having 2 gallons of fructose in 10 gallons of water; one has 20% concentration of sugar in solution (water).

Ionic bonds are bonds between atoms that, in essence, "steal" eachother's electrons. Certain elements have an affinity for being positive, called cations (e.g. Na+) and some for being negative, called anions (e.g. Cl-). This is determined easily by the position of the element on the periodic table. Metallic elements all tend to be cations. By each element carrying a countercharge (+vs-) the charges result in a neutral state hereby making ionically bonded compounds very stable- they have very high melting points and other interesting characteristics, and they are almost always soluble in water. Water is like an ionic compound (but it is not bonded ionically;next type of bond explains its system) in that it has a greedy charge distribution about its structure. You'll need to read a book to grasp all this stuff because I'm going over it all rather simply.

One other type of bond, the other main type, is called covalent bonding. This is where elements share electrons through a bond. A version of this bond is referred to as "polar covalent" meaning the electron density between the two elements bonded together is more positive at element A and more negative at element B, creating poles. Non-polar covalent, on the contrary, is an equal distribution of electron density between the elements involved in bonding.

I can barely begin to teach one chemistry on a forum, but I attempted to give you a quick run down. To understand chemistry, buy a textbook and begin to read it like a bible. As far as remembering things go, be sure to learn and understand all the trends in the periodic table for these will help you to become able to predict many simple reactions in chemistry. As Megalomania said, many complex reactions and most reactions that aren't routinely done in organic chemistry need to be experimentally tested to verify results. Once you learn basic chemistry, you'll be able to move on to organic chemistry where you'll find odd things in reactions like two reactants forming 4 different kinds of products because of certain conditions and behavior of the molecules involved. Sorry this has gone on far too long :)

[Lewis]

Kenno, if you are an electrician, that would mean you have taken all the high school courses nessicary to graduate, meaning you DID learn all this stuff at one point (probably).

I believe the basics of chem are learned at grade 10. If you flipped through some chemistry books, I'm sure your memory would be tweaked and you would remember a lot.

[megalomania]

In the US chemistry is grade 11, and then only for those who go the college prep route. This also assumes they have a well funded school district. I am lothe to imagine what some of the "urban" schools have for a chemistry program. Their knowledge of chemistry might well begin and end with freebase, baking soda, and cutting of product :)

[kenneo]

Hey fellas, just to reiterate on my purpose for posting this thread. It seemed as though everywhere I turned in my endevour to understand chemical reactions, there was always a reaction such as: (H + O --> H2O).

This seemed to me as something like a math problem, (or as easy as one) so I'm thinking, oh ya (1H) + (1O) = (H2O), suuuuure, oh wait a minute where the hell did that 2 come from? But as Mega pointed out, that chlorine is a diatomic molecule, aparently so too are Hydrogen AND Oxygen (I wasn't aware of this). So you actually get (H2 + O2 = H2O) thats better, but what the Fuck, shouldn't that be (H2 + O2 = H202) see I was thinking it was this easy, However I now know it is not.

To Lewis's Reply:Kenno, if you are an electrician, that would mean you have taken all the high school courses nessicary to graduate, meaning you DID learn all this stuff at one point (probably).

I did not graduate High School, rather I took the path of Mega's accurate presumption of rocking and chopping product, see for me it was another SIMPLE math problem MONEY + CANDY = PUSSY of which consumed most of my adolescent years,unfortunately (A lot of wasted Time).

Everything I've learned about the electrical field has been through rigorous self-study and on the job fuck ups. And I probably have a warped sense of electrical theory as well, but what I have learned helps me solve most problems which in turn allows me to pay my bills. Yet another SIMPLE math problem.

However I have reconciled to understanding more in depth the world in which we live and the way things within it are governed through chemistry. And have accepted that there is a whole shitload of material of which I am not familiar with, and which I must learn.

Thanks to you all for your replies.

[Lewis]

Okay, sorry for being presumptuous enough to assume you'd taken chemistry, I guess it's not as standard in the U.S. as I thought.

The reason why water forms in the reaction you described has more to it than the fact that both atoms are diatomic. It also involves the atom's charge, or number of bonds that it can form.

So think of the atoms as billiard balls, each with a different amount of sticks coming out of them. The 'sticks' are the bridges which can connect them to a different atom.

While the oxygen atom looks like this: --(O)--

The hydrogen atom looks like this: (H)--

And they COMBINE to form water, like this: (H)--(O)--(H)

Is this sheding any light on the subject?

[nbk2000]

Since when did we become an interactive classroom?

Let him figure it out on his own from here on.