Enthalpy Lab Background

Enthalpy, represented by the sign ? H in kJ/mol, is the heat change in a chemical chemical reception. It shows whether how much heat is released or absent-minded during the response. If the reaction is endothermic, the atomic bod 1 would be plus and if the reaction is exothermic, the enthalpy would be veto. During a chemical reaction, which consists of breaking and creating bonds, heat is either engrossed or released. In this lab, the reaction uses the disassociation of an ionic obscure ammonium ion ion treat shown in the comp be 1 below into ions.In order to disassociate ammonium nitrate into ions, nix is required. Both NH4 and NO3 be always soluble, therefore the ionic compound disassociates completely. Through comparability 2, heat absorbed or released rump be measured. In equation 2, q stands for the heat change in joules, m for the mass of the water in grams, C for the specific heat of water, and ? T for the change in temperature. By utilise the calorimete r with a stir rod, change in temperature is found. 1. NH4NO3(s) NH4(aq) + NO3(aq) 2. q=mC? TFree energy is a thermodynamic function that shows the available energy that fecal matter be converted into work. By victimisation the Gibbs-Helmholtz equation, which uses clean-handed energy and is shown in equation 3, spontaneity of the reaction fanny be found using enthalpy, temperature, and information. Free energy, remote information, is an absolute way to determine whether the reaction is spontaneous or non. If the free energy is negative, then the reaction is spontaneous, whereas if the free reaction is positive, then the reaction is not spontaneous.If free energy is neither, meaning if the free energy is zero, the reaction has reached equilibrium, therefore not faulting to left or right. In this lab, the reaction shown in equation 1 reaches equilibrium, so the free energy of this reaction would be zero. Entropy, shown by the sign S, is the measurement of molecular(a) randomness or put out. It is given in J/K*mol and it determines the disorder by the number of molecular arrangements that are possible in the state, whether it is solid, liquid, or gas.The more(prenominal) arrangements there smoke be, or larger amount of mole there is, the higher(prenominal) the data. If the change in haphazardness of a given reaction is negative, it pith that the reaction is increasing in order, or decrease in disorder. If the change in entropy of a given reaction is positive, it means that the reaction is increasing in disorder. Generally, negative entropy of a given reaction means that the reaction is spontaneous, but not always. Both equation 3 and 4 can be used to honour entropy. 3. ?G = ? H-T? S 4.? Sreaction=? pSproducts ? nrSreactants In equation 4, if the entropies of the molecules involved in the reaction are cognise, then change of entropy in the overall reaction can be found by subtracting the sum of the entropy of the products by the sum of the entropi es of the reactants. If the entropies of the molecules arent known like this lab, than equation 3 can be used to find the entropies of the reaction, where T represents temperature in Kelvin, ? G is the change in the free energy in kJ/mol, ? H is the change in enthalpy in kJ/mole, and ?S is the change in entropy in J/K*mol. The enthalpy of the reaction shown in equation 1 can be deliberate by the third equation using arithmetic because ? G is zero. And in this equation, the formula number 3, where ? G = ? H-T? S, Enthalpy must be greater that Entropy if the equation is to be positive. This is reason why this pry is sort out to zero, because then by subtracting the enthalpy the look upon of entropy can be found. And finished these methods, the value of G can be substituted in and to find the accepted value of ? H and ? S.The Kelvin is the accepted value, and the ? S can be found when plugged in ? H and ? G to be found as the zero value. The calculated entropy should match or be very close to the accepted entropy value for the dissolving of ammonium nitrate if the ionic compound is dissolved in water and the enthalpy determined by the calorimeter because the calorimeter shouldnt have lost each heat to surrounding and all of the solid should have been dissolved. Through this method, the absorbance rate of FeCl3 can be estimated, just like how NH4NO3 can be found.