CHEM 112 FACTORS THAT AFFECT REACTION RATES Introduction Rates of reaction are n
ID: 476434 • Letter: C
Question
CHEM 112 FACTORS THAT AFFECT REACTION RATES Introduction Rates of reaction are normally defined in terms of change of concentration of either a reactant or a product per unit with time. These reaction rates may simply be explained by collision theory. For almost reactions, species enough energy and the correct orientation so as to react. The required energies and orientations are specific to the reaction in question. The energy barrier to reaction is called the activation energy. The activation energy is related to the rate constant of the reaction, which in tum is related to the rate of the reaction by the rate law-Equation 2. The Ambenius equation relates R (8.314 J/mol-K) and the absolute he rate constant k, to the frequency factor A. the activation energy.E, the gas constant temperature T ation 3. The frequency factor is related to the frequency of collisions and the orientation of reacting species A B C+D+ From a mathematical inspection of the Amhenius equation it is seen that, as the temperature of the reaction is changed, the rate constant (and in fact the rate) of the reaction should change. The general "rule of thumb" is that every 10 K rise in the temperature will about a doubling (or up to a tripling change in the reaction rate (an equivalent lowering of result in the of the reaction rate). Also.as the nature of the reaction that slows exponentially while lowering As gets larger, the rate activation energy changes, the rate changes comespondingly. the energy barrier results in the reaction speeding up exponentially. These effects are seen in reactions by changing the mature of the reactants (e.g., the oxidation of different metals by aqueous acid) by introducing catalysts that lower the activation energy of the reaction being studied. are almost Even with the activation energy and temperature constant, there are other factors that affect reaction rates. These of the entirely due changes collision frequencies of the reacting species. the collision frequency changes surface area the rate reaction will change accordingly. Changing the concentration of those species in the rate law or changing the of a reagent in a heterogeneous reaction can change collision frequency reaction. Next week, we will Today we will qualitatively investigate a few of these factors that affect rates of quantitatively derive the the decomposition of hydrogen (part D) Procedure Materials: 020 M KI,0.10 M (NH..szo, ammonium peroxydisulfate).00020 M Nazsao, (sodium thiosulfate), starch solution, 6 M solutions of HCI, HNO, NH, HC,H,o, (acetic acid), and H,PO, 3% Hzo, 0.20 M MnCIz.Fe (nail, granular and powdered). Zn (20 mesh) and Al strips (1 x A. Effect oftemperature add 10.0 ml. of 00020 M Na.Sio,- To this add 6 drops of starch solution and 10.0 mL of 0.20 M KI. Mix thoroughly. To another beaker add 100 ml of 0.10 M (NHarsro.. Record the temperature of both solutions (they should be the same). Quickly pour the ammonium peroxydisulfate solution into the first beaker. Record the time it takes for the solution to turn blue (triiodide starch complex). Repeat this procedure at approximately 10 "C and 35 "C Reaction Temperature Beaker Beaker 6 drops 100 mL 100 mL 50 mL 00 mL Room Temperature About 10°C 100 ml 5.0 ml, 0.0 mLExplanation / Answer
1.
As the concentrations of reactants increases the rate of reaction also increases because there are more reactants to form products.
2.
As the concentrations of reactants increases the rate of reaction also increases because the number of collision between reacting molecules, as the result of these reaction rate will increased.