Heat of Neutralization 0368 Prepared by H. A Neidig, utanon Valley Collge, and 1

Question

Heat of Neutralization 0368 Prepared by H. A Neidig, utanon Valley Collge, and 1. N. Spencer, Franklin and Marshall Cllgr PURPOSE OF THE EXPERIMENT Determine the heat of neutralization for the reaction of sodium hydroxide (NaOH) and hydrochloric (HCD BACKGROUND INFORMATION The heat of neutralization (AHseutaa) is the heat transferred when 1 mol of an acid reacts with 1 mol of a base. This heat is generally reported in either kilo joules per mole kiloalories per mole (kal mol ly. reaction of HCI and NaoH solutions is shown in Equation 1. The heat of neutralization for a reaction cannot be measured directly. However, the heat transferred duringaneutralization reaction can be calcu- lated from laboratory data. In this experiment, you will determine the temperature change (Anfor a neutralization reaction as follows. In the laboratory, you will measure time-temperature data at alternate 30s intervals over a5min for NaoH solution and solution After you mix the two solutions, you will collect time-temperature data at 55 min and then at 1 min intervals over a 15 min period for the will find AT You will From time-temperature graphs of these data, you plot the temperature in degrees Celsius on the ordinate (y axis) You will plot the time in minutes of an interrupted temperature axis is a convenient way to plot such data. A plot time data is shown in Figure 1 on the next perpendicular After the data is plotted, will draw a vertical line, time of mixing. the raxis that represents the the x axis through the point line is called the line of mixing as shown in Figure 2 on the next page. This plotted points they Next you will draw the best straight line through the these lines so of each of the reactants. You will extrapolate the temp- intersect the line of The points where these lines the mixing are the initial temperatures of the reactants To calculate you will two i CENGAGE Learning

Explanation / Answer

[for data calculation, final temperature is needed to calculate dT value for the reaction]

Post lab

1. If the student failed to rinse the measuring cyllinder prior to measuring the base, some of base would get neutralized with the acid present in the cyllinder while measuring. Therefore the change in temperature dT in the experiment would now be lower due to lower actual moles of acid and base present. Thus, dHneutralization would also be lower than the expected value.

2. Effect of procedural changes on the final value

(1) Glass beaker is not fully insulated and thus heat is lost during the experiment to the atmosphere. The net change in temperature dT would now be lower and therefore the dHneutralization would also be lower than the expected value.

(2) When a pressed polystyrene top was used, no change in the results would be seen as the system is still fully insulated.

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