why does the catalyst decreases the activation energy of a chemical reaction?
971441
the catalyst helps the reaction proceed by allowing a separate path to reaction occur.  nature uses enzymes to do this, humans use organic and inorganic chemicals
228133
Basically to slow the reaction.  if you need more then here you go.\nsimply put heat is the measure of kinetic energy experianced by a substance either  molecularly or macrobiologically. the more abscence of heat means lower levels of energetic vibrations.  abosulte zero is a reflection of molecular stillnes.  if a reaction needs needs energy of some sort the the more energy delivered can increase the product of the reaction . look up la Chantiers principle.  by decreasing the energy level (activation energy) you there by decrease the rate of reaction (K) for a simplistic analogy, why do you but your food in thr refrigerator?  If i had $.50 cents yoou could buy a cupf coffee.  Read your Chem text.
375290
Generally chemical reactions slow down if the temperature goes down . . . . regardless of whether a catalyst is used or not. For enzymes (biological catalysts), the rule of thumb within normal (around room temperature) temperatures is that reactions slow down by half for every 10F reduction in temperature. It is important to note that this is only a rule of thumb and does not apply to all enzymes.
282222
Well, enzymes ARE catalysts, at least to my knowledge.\n\nThere isn't sufficient information to describe the collision rate. In Kinetics, we determine the collision rate using the rate equation, and that is determined using the R.D.S. (rate determining step) or slow step of the mechanism of the reaction... and since you have none of these in your question, it's really quite impossible to answer!
209054
Effect of enzyme on reaction
1151400
simply put: the higher the concentration the faster the reaction rate. in equilibrium the higher concentration shifts the reaction t o the other side.
1172999
1) exothermic reaction gives off heat\n2) a catalyst speeds up a rxn\n3) chemical reaction\n4) 1  + 4 --> 1 + 1 + 2\n\ncoefficiant of HCl is one
971455
there are various factors which affects rate of reaction. like temperature,pressure and concentration of the reactants involved. and they all have different effects
765354
a-decreases\n\nand only about 10% of the energy is actually passed on
1027970
Simply that during the induction period, the actual concentrations may not be 100% homogeneous and the rates will increase of decrease from theoretical.  This is much more important with macromolecules, but can be seen in other cases.  See\n\nwww.uem.mz/faculdade/ciencias/ ciencias_revista/textos/elalves.pdf\n\ndx.doi.org/10.1063/1.1954769\n\nwww.platinummetalsreview.com/ dynamic/article/view/50-2-54-63\n\nwww.citadel.edu/chemistry/scas2005.pdf
732299
The sign there is a chemical reaction is the fact there is heat being released.  Evidently, the reactant have more energy, because they are able to release that energy in the form of heat.
974474
The first answer is correct.\n\nThe second answer confuses kinetics with thermodynamics.  A catalyst only affects the rate of the reaction and has no bearing on the spontaneity of the reaction.  A catalyst is used in the Haber process to reduce the amount of residence time needed in the reactor.
421211
It is due to their unpaired electrons in the d orbital, and their ability to form a variety of oxidation states. This means they can readily accept and/or donate electrons to form intermediate compounds. This provides an alternative pathway for the reaction, with a lower activation energy, so it can take place at a faster rate. Once the intermediate compound reacts with another reactant, it will take back or return the electron(s) it used to the transition metal, therefore regenerating it.
320382
pressure adds energy increases the activation energy of the bonding reactions such that a different geometry is achieved
824613
Rate of chemical reactions depend on - temperature, pressure, concentration and the use of catalyst. The rxn constant (generally used in equilibriums) is often calculated to able to see the rate of the reaction. \n\nX + Y <----> 2V + Z\n\neq constant =  ([V^2]x[Z])/[X]x[Z]) \n\nThe higher the constant, the higher the rate. Equilibrium constant only changes if the there's a temperature change. Concentration changes doesn't effect the constant however it effects the rate. Although pressure changes lead to temperature changes, it's assumed that pressure changes don't effect the constant. If the constant is greater than 10^6, rxn will take place at reasonable rate.
854687
Temperature is a measure of the average kinetic energy in a substance. A catalyst reduces the activation energy required to go through a reaction. Energy is still usually required though. At lower temperature, there is a lower amount of energy so the process is slowed.
846677
Great question Angel V, you get a thumbs up, >from me<.\n\nAs you move down a group, metals become more reactive.\n\nThis is because of three reasons. \nI) Electrons farther from the nucleus are easier to get rid of because the positive nucleus is so far away\nII) Electrons farther from the nucleus already have lots of energy ready to be put to use in an exothermic process\nIII) Valence electrons have lots of electrons underneath them, causing what is known as shielding\n\nNote: I just thought I would add: It is not necessarelly true that the farther accross a period you go the elements are less reactive. For instance cadmium is more reactive than gold.