EXPERIMENTAL PROCEDURE nd the Pre-Laboratory Questions before coming to the labo

Question

EXPERIMENTAL PROCEDURE nd the Pre-Laboratory Questions before coming to the laboratory his seavear safety goggles when performing this experiment.) Sudy this section Capacity of the Calorimeter er in this experiment will consist oft . Heat two nested Styrofoam cups. Add to calorihu ahout 50. ml of approximately 2 M hydrochloric acid, HC1, solution. alomincarately in your graduated cylinder (LABORATORY METHODs B). Record your calorimeter urt and actual molarity of the HCl solution in TABLE 11.1A. velume of sodium neutralize your HCI solution Calculate the hydroxide, NaOH, solution (approximately 2 M) you need to volume plus an additional 3.0 mL in your graduated cylinder. Record the actual molarity of this NaOH solution in TABLE 11.1A. Put it into is mol volumse and the r. Measure the temperatures of both the HCI and the NaOH solutions. Be lrnse and wipe your thermometer clean before shifting from acid to base vice versa. Record these temperatures in TABLE 11.1A. Add 3 drops of ghemolphthalein to your HCI solution. the thermometer into the calorimeter. Pour the NaOH solution into the calorimeter, and stir very gently with your thermometer. Your mixture should be pink if ou have added enough base to neutralize the acid. At intervals of 15 seconds from the of mixing, read your thermometer to the nearest 0.1°C, and record the values in TABLE 11.1A. Continue stirring and recording the temperatures until the temperature of he solution has reached a maximum and has decreased for at least two consecutive readings. Do not miss the maximum temperature. It may occur between time increments. Clean and dry your apparatus, and repeat the experiment once or twice more as indicated by your instructor. B. Enthalpy Change for Reaction of Magnesium with Hydrochloric Acid Using an analytical balance, weigh 0.5 g of magnesium, Mg, turnings onto weighing paper, and record your masses in TABLE 11.1B. (Do not handle the magnesium with your fingers because grease from them will inhibit the reaction.) Place the magnesium in your clean, dry calorimeter. Add to a 250-mL or larger beaker about 50. mL of the EXPERIMENT 11 179

Explanation / Answer

1. The heact capacity of the calorimeter is the amount of heat absorbed by the calorimeter in which the experiment is conducted. Therefore, knowing the heat capacity of calorimeter can tell us how much heat is absorbed from the reaction (exothermic) by the calorimeter. The total heat change of the reaction is thus equal to the heat of solution + calorimeter heat capacity.

2. Reaction,

HCl + NaOH --> NaCl + H2O + heat

Total mass of soluton (m) = 50 + 50 = 100 g

density of H2O = 1 g/ml

so, volume = mass

heat capcity of water (Cp) = 4.18 J/g.oC

so,

knowing the temperature change (dT) after the two are mixed and the system is at equilibrium. The heat produced (q) by the reaction can be calculated using equation,

q = mCpdT

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