Question: Why does the temperature start to drop after a period of time? Questio

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Question: Why does the temperature start to drop after a period of time?

Question: How can we account for heat that is lost to our laboratory surroundings?
  

Part I: Measuing the temperature change for the acid-base neutralization reaction 1. Assemble the coffee-cup calorimeter as shown in Figure 1 above, with two nested StyrofoamB cups (a smaller one within a larger one) and with a thermometer supported either by a clamp or simply held by hand within the inner cup to monitor temperature changes during the reaction. 2. Add approximately 50.0 mL (record the volume to the nearest tenth in your lab notebook) of 2.00 M NH; (aq) (carefully record the molarity found on the bottle's label) to the calorimeter cup. 3. Measure and record the temperature of the NH,(a) in the calorimeter every 15 seconds for 3 minutes. You will use these data to establish a drift line that wil the initial temperature, Tinitial, of the reactants. 4. Using your graduated cylinder, obtain approximately 25.0 mL (record the volume to the nearest tenth in your lab notebook) of -2.00 M H2SO4(aq) (carefully record the molarity found on the bottle's label). 5. Add the sulfuric acid [H SO4a)] to the contents of the calorimeter [ie., to the NHs(ag) already in the calorimeter], stir continuously (carefully, using your thermometer) and continue recording temperature readings at 15 second intervals for 7 additional ninutes. Questiorn Was the reralization reaction exothermic or endothermic? How do you know? 49 Questior Why does the temperature start to drop after a period of time? Questiorn How can we accoum for heat that is lost to our laboratory swrowdings?

Explanation / Answer

Ans(1) Neutralization reactions are generally exothermic and thus H is negative.

Heat measurements are performed by carrying out the reaction in a special container called a calorimeter. The heat (Q) given off by the neutralization reaction is absorbed by the reaction solution and the calorimeter. Both the solution and calorimeter increase in temperature due to the absorbed heat and this increase can be measured with a thermometer. H is negative if heat is evolved and positive if heat is absorbed.

        -Hneutralization = QSolution + QCalorimeter

ANS (2) After some time Temperature of reaction mixture and temperature start to get in equillibrium , because temperature of reaction mixture is noew high and temperature of surroundings is low . So Reaction mixture loose some heat to surounding to lower it's temperature and temperature of surrounding increases by accepting this heat.

ANS (3) We can see heat lost to our laboratory surrounding by using themometer in surrounding .

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