DE Chemistry Unit 11_Thermochemistry_Review

ΔH value in an endothermic reaction is a positive number.

• True
• False

Calculate ΔH when 2 moles of ethanol (C₂H₅OH) reacts with excess oxygen according to the following thermochemical equation?

C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O ΔH = −1366.7 kJ

• -2733.4 kJ

• -683.35 kJ

• -1366.7 kJ

• -910.67 kJ

The specific heat(c) of copper is 0.39 J/g °C. What is the temperature change(∆t) when 100 Joules of heat(Q) is added to 20 grams?

• 12.82 °C
• 24.12°C
• 351 °C

When 15.0 grams of NaNO₃ is added to 100.0 grams of water at 20°C, the temperature of the water increases to 55°C. What is the q_rxn? Is the reaction endo or exo? (S_water=4.184)

• 14.6 kJ, endo

• -14.6 kJ, exo

• 2.20 kJ, endo

• -2.20 kJ, exo

(Hess's Law)Calculate the ∆H for the following reaction: 2H₂O₂ →  2H₂O  + 1 O₂ 
You are given these two equations:
2H₂  +  O₂ → 2H₂O            ∆H  =  -572 kJ
H₂  +  O₂  →  H₂O₂            ∆H  =  -188 kJ 

• ∆H  =  -948 kJ 
• ∆H  =  -196 kJ 
• ∆H  =  -384 kJ 
• ∆H  =  -188 kJ 

The standard enthalpy changes of formation of iron(II) oxide, FeO(s), and aluminium oxide, Al₂O₃(s), are –266 kJ and –1676 kJ respectively. Al and Fe are 0 kJ

What is the enthalpy change under standard conditions for the following reaction?

3FeO(s) + 2Al (s) --> 3Fe(s) + Al₂O₃(s)

• +878kJ

• –878kJ

• –1942kJ

• –2474kJ

Use bond energies to determine the energy change for the following reaction and use the information to determine if it is an endothermic or exothermic reaction:

HCN + H₂ --> CH₃N₂

The average bond enthalpies for O-O and O=O are 146 and 496 kJ/mol respectively. What is the enthalpy change, in kJ, for the reaction below?

H₂O₂(g) → H₂O(g) + ½O₂(g)

• -102

• +102

• +350

• +394

6. The formation ½ A₂ + 2 B₂ + C --> CAB₄ has an enthalpy of formation of -104 kJ and a change in entropy of -60.8 J/K at 30 °C. What is the free energy and spontaneity of the reaction?

• -85.6 kJ, spontaneous

• -18.3 kJ, not spontaneous

• +18.3 kJ, spontaneous

• +85.6 kJ, not spontaneous

At what temperature would a given reaction become spontaneous if ΔH =+119kJ and ΔS=+263J/K.mol

• 452 K

• 2210 K

• 382 K

• 363 K