Question

3. A 32.520 g piece of unknown metal was heated in a hot water bath at 99.80°C. The hot metal was then transferred to a coffee-cup calorimeter containing 100.0 mL of water. Time-Temperature data was collected and plotted. From the plot, the initial and final tem- peratures for the water were determined to be T 23.76°C and T 26.18°C. and qse (Assume C 21.0 J°C.) a. Calculate cal b. Calculate qnetal Calculate cmetal d. Calculate the molar mass for the metal and identify it using the Periodic Table.

Answer 1

3) a) Heat of calorimeter and heat of water is calculated:

q cal = Ccal * ΔT = 21 J / ° C * (26.18 - 23.76) ° C = 50.82 J

q water = m * cp * ΔT = 100 * 4.18 * (26.18 - 23.76) = 1011.56 J

b) The heat of the metal is calculated:

q metal = - q cal - q water = - 50.82 - 1011.56 = - 1062.38 J

c) The specific heat of the metal is calculated:

C metal = q / m * ΔT = -1062.38 / 32.52 * (26.18 - 99.80) = 0.444 J / g * ° C

4) a) The reaction that occurs is:

H2SO4 + 2 NaOH = Na2SO4 + 2 H2O

b) The calorimeter and solution heats are calculated:

q Cal = 21 * (31.2 - 22.3) = 186.9 J

q solution = 50 * 4.18 * (31.2 - 22.3) = 1860.1 J

c) The heat of reaction is calculated:

q rx = - 186.9 - 1860.1 = - 2047 J

d) The heat of reaction is calculated:

ΔH = - 2.05 kJ / 1 M * 0.025 L = - 82 kJ / mol

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