A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking of chemical bonds between atoms, with no change to the nuclei (no change to the elements present), and can often be described by a chemical equation. Nuclear chemistry is a sub-discipline of chemistry that involves the chemical reactions of unstable and radioactive elements where both electronic and nuclear changes can occur.
The substance (or substances) initially involved in a chemical reaction are called reactants or reagents. Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. Reactions often consist of a sequence of individual sub-steps, the so-called elementary reactions, and the information on the precise course of action is part of the reaction mechanism. Chemical reactions are described with chemical equations, which symbolically present the starting materials, end products, and sometimes intermediate products and reaction conditions.
Chemical reactions happen at a characteristic reaction rate at a given temperature and chemical concentration. Typically, reaction rates increase with increasing temperature because there is more thermal energy available to reach the activation energy necessary for breaking bonds between atoms.
Reactions may proceed in the forward or reverse direction until they go to completion or reach equilibrium. Reactions that proceed in the forward direction to approach equilibrium are often described as spontaneous, requiring no input of free energy to go forward. Non-spontaneous reactions require input of free energy to go forward (examples include charging a battery by applying an external electrical power source, or photosynthesis driven by absorption of electromagnetic radiation in the form of sunlight).
A reaction may be classified as redox in which oxidation and reduction occur or nonredox in which there is no oxidation and reduction occurring. Most simple redox reactions may be classified as combination, decomposition, or single displacement reactions.
Different chemical reactions are used during chemical synthesis in order to obtain a desired product. In biochemistry, a consecutive series of chemical reactions (where the product of one reaction is the reactant of the next reaction) form metabolic pathways. These reactions are often catalyzed by protein enzymes. Enzymes increase the rates of biochemical reactions, so that metabolic syntheses and decompositions impossible under ordinary conditions can occur at the temperatures and concentrations present within a cell.
The general concept of a chemical reaction has been extended to reactions between entities smaller than atoms, including nuclear reactions, radioactive decays, and reactions between elementary particles, as described by quantum field theory.
Hi there in my knwoledge the energy released in any nuclear reaction is because of the fact that the mass off the reactants is greater than the mass of the products and the missing mass is converted into energy but in a nuclear reaction the bindind energy of the products is greater than that of...
Homework Statement
Find the reactions exerted on the members by the supports.
Homework Equations
Sigma Fx = Net force acting on x-axis = 0
Sigma Fy = Net force acting on y-axis = 0
Sigma M = Net Moments = 0
The Attempt at a Solution
10N/m -> changes to 4N at centre acting...
Homework Statement
Calculate the value of the equilibrium constant at 25 degrees celsius for the following reaction:
5Fe2+ + MnO4- + 8H+ ----) 5Fe3+ + Mn2+ + 4H2O
Homework Equations
The equation above is the product of these redox reactions:
1) MnO4- + 8H+ + 5e- ----) Mn2+ + 4H2O E=...
I'm just curious, what was the first reactions to Einstein's theories (it was 1905, right?) ... were they refuted or supported?
was it like "Oh! these are nonsense..these are pseudoscience .. we shall burn you"?!
or were they garnered respectable amount of debate?... were they supported by...
In neutron activations, target materials are being beamed by high energy flux, thus making the target materials excited and undergo radioactive decay. Neutron analysis then can be performed after the materials are "cool" enough by placing inside the hood with enough shielding.
My question is...
Hello,
If a reaction is spontaneous when calculated using Gibb's Free Energy formula,
Delta G = Delta H - (T*Delta S)
Does it mean the reaction will occur at impossible temperatures even (such as 999999999999999999999999 degrees Kelvin)
for ex:
H2O(g) C(s) --> CO(g)+H2(g)
Delta H =...
Homework Statement
Homework Equations
ΔH rxn = ΔH products - ΔH reactants
ΔU = q + w
The Attempt at a Solution
Pretty overwhelmed with the entire problem. Since the ΔH's of all reactants and products were in the literature for the reference temperature of 298.15 K, I was able to...
Homework Statement
If the following substances were heated what gas would be given off and what solid would remain? strontium carbonate, zinc carbonate, and iron carbonate.
Homework Equations
N/A
The Attempt at a Solution
So I presume carbon dioxide would be given off and the 3...
Hi,
I know that there are a number of different ways that uranium-235 can decay when a slow neutron collides with it.
I am trying to get a picture of all the possible reactions that can occur.
One is U-235+n --> Ba-144 + Kr-90 +2n
Another is: U-235 +n --> Xe-140 + Sr-94 +2n
Can anyone give...
Homework Statement
Homework Equations
Kc = (Kp)/ (RT)delta n
K_c = (K_a)(K_b)
(Where a and b are the individual reactions while c is the overall reaction where the coefficients are the same)
The Attempt at a Solution
The question prior to this one has individual reactions as...
Hello everybody,
I am having some troubles with this exercise. I have attached the text and the solutions to my post. My problem is, after I have coupled the angular momenta and used the CK coefficients like in (|\pi ^{+}p>=|1,1>|1/2, 1/2>=|3/2,3/2>) (pag.432) I don't understand what...
Hi, I just learned about oxidation and reduction reactions and I have some questions.
Are all ionic reactions redox reactions?
Do elements that make up covalent compounds always have an oxidation number of zero because they only share electrons, not give or take? That is what I was thinking...
Nuclear reactions in which the Q value is negative (endothermic reactions) imply that energy is absorbed in the process of the reaction. Is this to be interpreted as a case where the initial rest mass energy is less than the rest mass energy of the products of the reaction? If affirmative, it...
I found this the other day and it made me think of Danger and Artman from the The Thread Killers Thread.
Kurdt says the video is ok, and he's a prude.
Hope you enjoy!
Homework Statement
I'm to design a crane, and therefore I need to find the reactions in the jib and also make the crane stable.
1. I need to find the max. load that the crane is able to lift. Therefore i have to find the reactions where the horisontal and vertical boom is meeting.
2. I need...
Homework Statement
Determine the support reactions for the given structure(see attachment) due to flexural deformations using castigliano's second theorem. Axial deformations are considered negilible.
Homework Equations
delta = dU / dP
The Attempt at a Solution
See attachment. I could use...
OF2 --> F- + O2 + H2O
OF2 --> F-
2H+ +OF2 --> 2F- + H2O
2H+ +OF2 + 4e- --> 2F- + H2O
This is as far as I can get. I don't know how to do the other half of the redox since the equation would be:
OF2 --> O2 + H2O
What do I do here? Maybe I am not setting this up correctly?
Homework Statement
Balance the following redox reactions occurring in an acidic solution.
Homework Equations
PbO2(s)+I-(aq)---->Pb2+(aq)+I2(s)
The Attempt at a Solution
1.) half reactions:
a.) reduction: I-(aq)----->I2(s)
b.) oxidation: PbO2(s)------>Pb2+(aq)
2.) balance...
Homework Statement
"A lifting mechanism is mounted on the back of a truck as shown: Calculate the forces in each member and the reactions @ A & B for alpha=0
Homework Equations
Sum of moments about A=0:
0=(5000N)(1m)+(-5000N)(-1.25m)+(By)(.5m)
By=2500N
The Attempt at a...
Hi, can anyone show the correct method of how to solve a problem like this. Got the answers from my book but have no idea how they get them?
Thanks
James
I'm having a lot of trouble with this problem!
What mass of lead sulfate is formed in a lead-acid storage battery when 1.34 g of Pb undergoes oxidation?
the answer needs to be in grams
Hey I'm studying for my chem exam & I am having difficulty solving some problems.
1. 1,3cyclohexadiene + Br2= ?
Here,should i treat it like a conjugated diene? Meaning that the Br molecules will have 1,2 and 1,4 additions on the diene and 2 products will be there?
2. 1,4cyclohexadiene +...
I'm writing a book but my chemical knowledge is near non-existent and I need a TRUE scientific reason as to why warewolves would be 'allergic' to silver. I know I could make something up but I would like to have as much fact as I can when it comes to stuff like this. It'll help me stand out.
Homework Statement
One of the thermonuclear or fusion reactions that takes place inside a star such as our Sun is the production of helium-3 (3He, with two protons and one neutron) and a gamma ray (high-energy photon, denoted by the lowercase Greek letter gamma, ) in a collision between a...
Homework Statement
Hope you can access this link for question http://s353.photobucket.com/albums/r387/james_nikko/?action=view¤t=img002.jpg
Supports are at 1.5m and 4.5m
Homework Equations
The Attempt at a Solution
Ok so i have attempted the problem using the following
(5x1.5) + (5x3)...
I was taught in high school that all reactions are governed by the valence electrons. of the atoms involved.
Then I was taught that the term "redox reaction" applied only to rxns where e- were exchanged, or oxidation numbers were changed.
But the first fact would lead me to believe that...
Hey.
Im currently doing a course in numerical analysis, and while most of the focus is on the mathematics side of things, the assignments are set in an engineering context.
One of my assignments describes a beam that is "pin jointed" at both ends, is 1 meter long, and is subject to a 0.5 N/m...
Homework Statement
The pipe assembly shown in the picture supports the vertical loads shown. Determine the reactions at the ball and socket joint (point A) and the tension in the two cords BC and BD.
Homework Equations
Sum of Forces = 0
Sum of Moments = 0The Attempt at a Solution
I first...
I was wondering how come when ever there's a question like aluminum reacts with bromine it is usually written like Al + Br2? or Potassium reacts with oxygen is K + O2?
How do we know when there's 2 of them?? Is there like a special rule? Why isn't there K2 or Al2??
Homework Statement
1. A flask initially contains only NOBr gas. Once heated to a temperature T, 34.0 % of the original gas decomposes via the following equation to give a total pressure of 0.25 atm at equilibrium:
2NOBr(g) \Leftrightarrow 2NO(g) + Br2(g)
Given a KC of 3.94 x 10-4 I...
Where does most of the heat energy in fission reactions come from?
-Does it come from radiation emitted from particles leaving the nucleus?
-Does it come from those actual particles leaving the nucleus and hitting surrounding gases in the air, causing them to move and heat up?
-Something...
Expansion Work -- Still confused.
This is more of a general question regarding thermodynamics. If you have a combustion reaction, and it produces either liquid water or water vapor--which case results in higher expansion work? My enthalpy calculations show higher PV work for the reaction with...
Hi guys today in the lab i did reaction of barium chromate with hydrochloric acid and when i add HCL to barium chromate i got a reddish orange solution but when i add sulphuric acid i got a colorless solution with yellow ppt. Why is this so? Shouldn't both give me the same result since they are...
Organic Chemistry Reactions - Check my Answers, Please! :)
this is the lab that we have to do in class:
http://academics.eckerd.edu/instructor/grove/gorgchem/Extraction%20Lab.pdf
http://picasaweb.google.com/lh/photo/cnIZmcws9cN3v_1TDx7nfg?authkey=Gv1sRgCI-xv4Hl9tampgE&feat=directlink
Homework Statement
HIO3 + FeI2 + HCl ==> FeCl3 + ICl + HOH
Homework Equations
Directions say it's in an aqueous solution, and HCl is a reactant, so you can add H2O and H+ to balance, right?
The Attempt at a Solution
I first found all the oxidation states:
HIO3
H = +1
I = +5
O...
Homework Statement
Find whether the following is spontaneous. Forward= (process as written), backwards, both or none
Homework Equations
1. water & syrup mixed to give a flavoured drink
2. Piece of paer at room temp react with O2 to give CO2 and H2O
3. Bathtub water gets cold after you...
In the BBC film Einstein and Eddington, Eddington describes the theory of spacetime using a table cloth (space), a loaf of bread (sun) and a piece of fruit (a planet).
The Bread is placed in the middle of the table cloth, this forms curves in the cloth. He then takes a piece of fruit and...
Homework Statement
Describe the preparation of 40 L of 0.0500M phosphate buffer, pH 6.9 starting with 1M solutions of KH2PO4 and K2HPO4. pKa= 7.2Homework Equations
pH= pKa + log[A-]/[HA][b]3. The Attempt at a Solution [/b
6.9=7.2 + log[A-]/[HA]
-0.3= log[A-]/[HA]
[A-]/[HA]= 0.50
0.5[HA]=...
balance the following oxidation reduction reactions. which is the oxidizing agent? reducing agent?
()my answer as balance
a) P4 + Cl2 =(4)PCl5 reducing agent P, o agent Cl
b) Sn2+ + Cu2+ = Sn4+ + Cu+ reducing agent...
i know no one can diagnose me on here, I'm just looking for opinions and maybe guidance to things to research.
my body has a strange way with medicine. 98% of the drugs I've taken (legal and otherwise...) don't work as they are supposed to. i usually have to take a double or triple dose to...
Hi,
I'm in first year organic chem and we're obviously learning about all the different reaction mechanisms (e.g. elim reactions of alcohols) and I was wondering if the only way to figure out what is going to happen in a particular reaction is to memorize all these different reaction...
Homework Statement
When copper metal is placed in a beaker containing a solution of silver nitrate, a reaction occurs which can be represented by the following equation:
2AgNO3(aq) + Cu(s) -----> Cu(NO3)2(aq) + 2Ag(s)
a) Give the net ionic equation to represent this reaction occurring...
Hello everyone :smile:
I'm just wondering why is cooling considered to slow reactions. I mean f you want condensation heating would slow the reaction. I like to know exactly how condensation occur at molecular level. I know when you heat gas it expands. So when you cool a gas does it...
like mixing household chemicals together to get a cool reaction to help my brother for the science fair? please don't say baking soda and vinegar half the school is doing that for a volcano.
Homework Statement
What concepts from Thermodynamics govern whether reactions occur or not?
Homework Equations
The Attempt at a Solution
Activation energy-need some source of energy to start it-like pressure or light.
Entropy-but why?
Anything else, I'm sure there is more...