I need help with the questions plz ENTHALPY OF A CHEMICAL REACTION All chemical

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I need help with the questions plz

ENTHALPY OF A CHEMICAL REACTION All chemical reactions involve an exchange of heat energy; therefore, it is tempting to plan to follow a reaction by measuring the enthalpy change (A), However, it is often not possible to directly measure the heat energy change of the reactants and products (the system). We can measure the heat change that occurs in the surroundings by monitoring temperature changes. we conduct a reaction between two substances in aqueous solution, then the enthalpy of t reaction can be indirectly calculated with the following equation. he Eqn. 1 The term q represents the heat energy that is gained or lost. C, is the specific heat of water, m is the mass of water, and T is the temperature change of the reaction mixture. The specific heat and mass of water are used because water will either gain or lose heat energy in a reaction that occurs in aqueous solution. Furthermore, according to a principle known as Hess's law, the enthalpy changes of a series of reactions can be combined to calculate the enthalpy change of a reaction that is the sum of the components of the series. In this experiment, you will measure the temperature change of two reactions, and use Hess's law to determine the enthalpy change, AH of a third reaction. You will use a Styrofoam cup nested in a beaker as a calorimeter, as shown in Figure 1. For purposes of this experiment, you may assume that the heat loss to the calorimeter and the surrounding air is negligible. 0 Figure I

Explanation / Answer

Answers

1. The new technique learnt in the lab was determination of heat of neutralization, and heat of reaction using styroform cup. It is asumed that no heat is lost of gained to or from the surrounding in these experiments. Hess's law was used to calculate heat of reaction from two processes.

2. Hess's law

Reaction 1 : NaOH + HCl ---> NaCl + H2O                dH = 54.03 kJ/mol

Reaction 2 : NH4Cl + NaOH ---> NH4OH + NaCl      dH = 4.564 kJ/mol

invert Reaction 2 and add Reaction 1 and inverted Reaction 2,

NH4OH + NaCl ---> NH4Cl + NaOH

NaOH + HCl ---> NaCl + H2O

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NH4OH + HCl ---> NH4Cl + H2O   dH = 54.03 - 4.564 = 49.466 kJ/mol

So the enthalpy for Reaction 3 = 49.466 kJ/mol

3. The literature value of enthalpy for Reaction 3 when compared with,

- The enthalpy value calculated for Reaction 3 by Hess's law is slightly lower than the reported value for it

- The enthalpy value calculated experimentally is close to the enthalpy reported in the literature.

4. The experiment thus supports Hess's law completely. We could improve our experiment by making sure the volumes taken of the reactants are accurate. No heat is lost or gained from the system and measuring the temperatures after calibration of the system.

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