Temperature of chemical reaction – one of the major factors influencing its speed. According to Vant Hoff's rule, at temperature increase the speed of homogeneous elementary reaction increases by 10 degrees by two-four times. It is necessary to consider that this rule works only in rather narrow temperature range and is inapplicable at the big sizes of molecules – for example, in a case with polymers or proteins. How to determine temperature of chemical reaction?
It is required to you
- - trekhgorly flask from refractory glass from a shlifama;
- - drop funnel with shlify;
- - the long laboratory thermometer with shlify (an interval of measurements – from 100 to 200 degrees);
- - torch with a sandy bath;
- - all necessary for collecting distillate (adapter, fridge, reception capacity);
- - the concentrated sulfuric acid;
- - the concentrated acetic acid;
- - ethyl alcohol.
Instruction
1. Let's review a concrete example – synthesis of ethyl acetate during etherification reaction. In a flask which bottom is placed in a sandy bath pour equal volumes of ethanol and sulfuric acid (we will assume, on 10 ml). Insert the thermometer into one of "throats". But consider that it is necessary to pick up in advance the thermometer of such length that its mercury tip was in mix, but did not concern a flask bottom. Insert a drop funnel into other "throat". Through central "throat" couples of products of reaction will depart.
2. Heat ethanol and sulfuric acid on a sandy bath to 140 degrees then begin to flow on drops mix from ethyl alcohol and acetic acid.
3. Soon in reception capacity the condensed distillate will begin to gather. It means that ethyl acetate began to be formed. It is possible to determine by the thermometer at what temperature of mix there is a reaction.
4. In some cases it is possible to determine temperature of chemical reaction, using a formula of energy of Gibbs: ∆G = ∆H - T∆S. It is easy to find the size of energy of Gibbs, an enthalpy and entropy of many concrete reactions in any reference book on chemical thermodynamics. The unknown will remain only size T – reaction temperature in degrees Kelvin which very easily can be calculated on a formula: T = (∆H - ∆G) / ∆S.