Speed of chemical reaction is the change of amount of substance in unit of time happening in reactionary space. Speed of chemical reaction – size always positive. Even if reaction proceeds in the opposite direction and concentration of initial substance decreases, speed is multiplied by-1.
Instruction
1. The science which studies change of concentration of reagent in unit of time is called chemical kinetics. Besides speed, this discipline and studying factors on which it depends is engaged.
2. To learn concentration of the dissolved substance, it is necessary to know how many his moths on an amount of water were dissolved. If these values are not given you in a statement of the problem, weigh substance and divide the turned-out value into molar weight. Concentration of substances has mol/litre unit of measure.
3. To calculate the speed of chemical reaction, you will need knowledge of initial and final concentration of reagent. Take away the second result from the first, and you learn what amount of substance was spent. This figure needs to be divided into the number of seconds for which these changes managed to happen. Mathematically the formula looks as υ = s ⁄∆ t where With – a difference of concentration, and t – time interval.
4. Concentration of substance is expressed in the moths divided into liters, time – in seconds. Therefore, the speed of chemical reaction is measured in mol/l. x sec.
5. Speed of chemical reaction can be calculated also by quantity of the formed product. Take zero for initial concentration, and increase the turned-out negative result by-1.
6. Speed of chemical reaction is changeable. In the beginning, when concentration of substances is highest, their particles face among themselves much more often therefore the final product is formed quicker. Then the speed of course of reaction slows down. Chemists entered the concept "reaction speed constant". It is the size which is in number equal to reaction speed while concentration of substances reaches 1 mol/litre. There is a constant on Arrhenius's equation: k=Ae in degree – Ea/Rt, where And – the frequency of collisions of molecules, R – a universal gas constant, Ea – energy of activation, and t – temperature.