Experiment 14 Advance Study Assignment: Heat Effects and Calorimetry I. A metal

Question

Experiment 14 Advance Study Assignment: Heat Effects and Calorimetry I. A metal sample weighing 71,9 g and at a temperature of 100,0°C was placed in 41.0g of water in a calorimeter at 24.5°C, At equilibrium the temperature of the water and metal was 35.00. a. What was for the water? (s-tu" 'ital) °C b. what was for the metal? oc c. How much beat flowed into the water? joules d. Taking the specific heat of water to be 4.18 J/g C, calculate the specific heat of the metal, using Equation 3. Joules/rc What is the approximate molar mass of the metal? (Use Eq. 4.) e. 2. When 2.0 g of NaOH were dissolved in 49,0 g water in a calorimeter at 24.0°C, the temperature of the solution went up to 34.5°C a. Is this solution reaction exothermic? Why? b. Calculate 9no using Equation 1 joules c. Find AH for the reaction as it occurred in the calorimeter (Eq. 5) joules (continued on following page)

Explanation / Answer

1. (a) t = tfinal -tinitial
tfinal = 35.0 0C
tinitial = 24.5 0C
t for water = (35.0-24.5) = 10.5 0C

(b) Similarly
tfinal = 35.0 0C
tinitial = 100.0 0C

t for metal = (34.5-100.0) = - 65.5 0C

(c) qwater = (mwater) (swater ) (twater )

where qwater = heat flowed into water

mwater = mass of water
swater = specific heat of water ( value = 4.184 J/gram °C)
qwater = (41.0 g) (4.184 J/g oC) (10.5 0C ) = 1.801 * 103 J

(d) Specific heat of metal = qmetal / (mmetal * t metal )
     qmetal = - qwater = -1.801 * 103 J
Specific heat of metal = -1.801 * 103 J/ (71.9 g) (-65.5 oC) = 0.382 J/g oC

(e) As per law of Dulong and Petit ; (Specific heat of metal ) (molar mass) = molar heat capacity of solids

Value of molar heat capacity of solids is 24.9 J K-1mol-1

(0.382 J/g oC ) *molar mass of metal ) = 24.9 J K-1mol-1
molar mass of metal = 65.18 g mol -1

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