1). A 55.5 g sample of water at 99.8C is placed in a constant pressure calorimet
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Question
1). A 55.5 g sample of water at 99.8C is placed in a constant pressure calorimeter. Then, 23.3 g of zinc metal at 21.2??C is added to the water and the temperature drops to 96.4??C. What is the specific heat capacity of the zinc metal measured in this experiment?
2). A 26.4 g sample of aluminum at 100.0??C is added to 100.0 g of water at 21.7??C in a constant pressure calorimeter. What is the final temperature of the water?
3). When 0.100 g of Zn(s) combines with enough HCl to make 55.0 mL of HCl(aq) in a coffee cup calorimeter, all of the zinc reacts, which increases the temperature of the HCl solution from 23.0 ? C to 24.5? C: Zn(s) + 2HCl(aq) ? ZnCl 22 (aq) + H 22 (g) Calculate the enthalpy change of the reaction ? H rxn .
(Assume the density of the solution is 1.00 g/mL and the specific heat capacity of solution is 4.184 J/gC.)
Zn(s) + 2HCl(aq) ? ZnCl2(aq) + H2(g)
4). The combustion reaction of nitromethane fuel occurs as follows:
2 CH3 NO2 (l) + 3/2 O2 (g) ? 2 CO2 (g) + 3 H 2 O(l) + N2 (g)
The standard enthalpy of this reaction is –1418 kJ. What is the standard enthalpy of formation of nitromethane?
5). Calculate the enthalpy of reaction ( ?? H rxnrxn ) for the following reaction:
Fe 2 O3 (s) + 3 CO(g) ? 2 Fe(s) + 3 CO2 (g)
Given:
4 Fe(s) + 3 O 2 (g) ? 2 Fe2 O 3 (s) ?? H = –1648 kJ
2 CO2 (g) ? 2 CO(g) + O2(g) ?? H = +565.4 kJ
THANK YOU.
2). A 26.4 g sample of aluminum at 100.0??C is added to 100.0 g of water at 21.7??C in a constant pressure calorimeter. What is the final temperature of the water?
Explanation / Answer
1)
m(water) = 55.5 g
T(water) = 99.8 oC
C(water) = 4.184 J/goC
m(zinc) = 23.3 g
T(zinc) = 21.2 oC
C(zinc) = to be calculated
We will be using heat conservation equation
use:
heat gained by zinc = heat lost by water
m(zinc)*C(zinc)*(T-T(zinc)) = m(water)*C(water)*(T(water)-T)
23.3*C(zinc)*(21.2-96.4) = 55.5*4.184*(96.4-99.8)
C(zinc)= 0.4506 J/goC
Answer: 0.451 J/goC
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