2. Write chemical equations for the TWO reactions we are going to study: 2 Na OH

Question

2. Write chemical equations for the TWO reactions we are going to study: 2 Na OH H2504 2 H20 No2 S04 NaOH HC -- NaCl + H2O 2. reaction? Is heat a reactant or a product in this reaction? How will we use this to monitor the extent of 3. Suppose you had the following reaction: HBr (aq)+ NaOH (ag)NaBr (aq)+ H,0 ()+ heat If you started with 3 mol of HBr and added 2 mol of NaOH, would you expect the heat released to be at its maximum? Why or why not? 4. In this reaction we will be adding different amounts of the two reactants in each trial. What, however, will we be keeping constant throughout? TA Name:- T4 Initial: Page 65 Chem 4 2017

Explanation / Answer

Ans. #2. Heat is the product in acid-base neutralization reactions.

At the point of completion of reaction, i.e. complete neutralization, the increase in temperature of the reaction mixture would be highest. To keep a track of completion of neutralization reaction, monitor the increase in temperature of the reaction, The point at which there in more increase in temperature is taken as the endpoint/completion of the reaction. Because when reaction is complete, no more heat would be produced, so no more increase in temperature can be recorded.

#3. No.

1 mol HBr is neutralized by 1 mol NaOH.

In a reaction mixture of 3 mol HBr and 2 mol NaOH, the base NaOH acts as the limiting reactant. So, 2 moles of HBr would be neutralized and 1 mol HBr is left behind.

The energy released during neutralization of 2 mol HBr forming 2 mol water of neutralization = 2 mol x enthalpy of neutralization

                                    = 2 mol x (-57.1 kJ/mol)

                                    = -114.2 kJ

If there are 3 moles of each reactant, there would be 3 moles of water of neutralization formed.

The energy released during neutralization of 3 mol HBr forming 3 mol water of neutralization = 3 mol x (-57.1 kJ/mol)

                                    = -171.3 kJ

# Therefore, the given reaction mixture produces less than maximum possible heat due to incomplete neutralization of the acid.

#4. Note that NaOH remains common to both the reactions.

So, the experiment is designed as follow-

            I. A fixed volume of standard NaOH is taken in two tubes

            II. H2SO4 is added to first tube. HCl is added to the other tube.

So, in each trial NaOH is kept constant.

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