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Transcript
Chemistry
Random Problems
Name:
Date:
Hess’s Law
1. Calculate the ΔH for the synthesis of diborane, B2H6.
2 B(s) + 3 H2(g) ---> B2H6(s)
Givens:
2B(s) + 3/2 O2(g) ---> B2O3(s)
B2H6(g) +
H2(g)
+
H2O(l)
Δ H=-1273 kJ
3O2(g) ---> B2O3 +
1/2 O2(g) --->
--->
Δ H=-2035 kJ
3 H2O (g)
Δ H=-286 kJ
H2O (l)
Δ H= 44 kJ
H2O(g)
Δ H=_______
+
N2
----->
2NO
2. Calculate the ΔH for the reaction
O2
Givens:
+
O2
1/2N2
----->
NO2
ΔH
= +67.6 kj/mol
NO
1/2O2
----->
NO2
ΔH
= -56.6 kj/mol
+
Δ H=_______
Specific Heat
3. How much heat is necessary to raise the temperature of 25.00 g of water from 10.oC to 60.oC.
4. A piece of metal with a mass of 5.19 g is heated to 100.0oC and dropped in 10.0 ml of water at 22.0oC. The final
temperature of the system is 23.83oC. What is the specific heat of the metal?
Enthalpy and Entropy
5. What is the ΔH, ΔS, and ΔG for the following reaction. Fe2O3(s) + 3 CO(g) ---> 2 Fe(s) + 3 CO2(g)
Also, list if it is exo/endothermic, more/less ordered, and if it is spontaneous forward or backwards.
6. What is the ΔG value for a reaction with the following characteristics: ΔH=-135kJ/mol, ΔS=36J/(mol*K), and at 293K?
Will the reaction occur spontaneously at that temperature?
Enthalpy Lab Calculation
7. Imagine the following lab situation and calculate the Δ HR for the neutralization of Hydrochloric Acid with Sodium
Hydroxide.
Procedure:
50mL of 2M NaOH was added to 50mL of 2M HCl in a colorimeter. The mass of the solutions together was 100g.
Data:
Trial 1
Trial 2
Trial 3
HCl
Ti: 20.3oC
20.1 oC
20.2 oC
After Neutralization
Tf: 29.6oC
29.4 oC
31.3 oC
ΔT1=
ΔT2=
ΔT3=
Using the specific heat of water, calculate the energy of the reaction.
Trial 1
Trial 2
Trial 3
Using the Molarity and Volume of NaOH, calculate the moles of NaOH.
Calculate the ΔHR in kJ/mol.
Trial 1
Average the Trials.
Trial 2
Trial 3