1) What quantitiy in moles of oxygen is consumed when 369.3 kJ of energy is evol
ID: 476461 • Letter: 1
Question
1) What quantitiy in moles of oxygen is consumed when 369.3 kJ of energy is evolved from the combustion of a mixture of H2 (g) and O2(g)? H2(g)+ 1/2 O2 (g) H2O (l) Enthalpy of reaction= -285 kJ/mol-rxn
A. 0.1461 mol
B. 0.646 mol
C. 0.3869 mol
D. 1.146 mol
E. 1.292 mol
2. Combustion of 7.21 g of liquid benzene (C6H6) causes a temperature rise of 50.3 C in a constant pressure calorimeter that has a heat capacity of 5.99 kJ/C. What is delta H for the following reaction?
C6H6(l)+15/2 O2(g) 6 CO2 (g) + 3 H2O (l)
A) 302 kJ/mol-rxn
B) 41.8 kJ/mol-rxn
C) -3.27x10^3 kJ/mol-rxn
D) -302 kJ/mol-rxn
E) -41.8 kJ/mol-rxn
3) CaO (s) reacts with water to form Ca(OH)2 (aq). If 6.50 g CaO is combined with 99.70 g H2O in a coffee cup calorimeter the temperature of the resulting solution increases from 21.7 C to 43.1 C. Calculate the enthalpy change for the reaction per mole of CaO. Assume specific heat capacity of solution is 4.18 J/g*k
A) -165 kJ/mol
B) -532 kJ/mol
C) -82.0 kJ/mol
D) -9.42 kJ/mol
E) -1.45 kJ/mol
4) Which of the following reaction corresponds to the thermochemical equation for the standard molar enthalpy of formation of solid calcium nitrate?
A. Ca(OH)2 (s) + 2HNO3 (aq) Ca(NO3)2 (s) + 2H2O(l)
B. Ca2+ (aq)+2NO3- (aq) Ca(NO3)2 (s)
C. Ca(s) + 2HNO3 (aq) Ca(NO3)2 (s) + H2 (g)
D. Ca(s)+2N(g) + 6 O(g) Ca(NO3)2 (s)
E. Ca(s) + N2(g) + 3O2(g) Ca(NO3)2 (s)
5) Calculate enthalpy reaction for the combustion of ammonia.
4 NH3(g) + 7 O2 (g) 4 NO2(g) + 6 H2O (l)
Using standard enthalpy of formation
A. -298.6 kJ/mol-rxn
B. -1398.8 kJ/mol-rxn
C. -206.9 kJ/mol-rxn
D. +30.24 kJ/mol-rxn
E. -1663.6 kJ/mol-rxn
Molecule Enthalpy of formation (Delta H) NH3 (g) -45.9 NO2 (g) + 33.1 H2O (l) -285.8Explanation / Answer
1. From the given reaction, 285 kJ/mol is evolved when 0.5 moles of oxygen is consumed.
If 369.3 kJ is evolved, then oxygen consumed be
= 369.3/(285/0.5)
=0.648 moles
Option B is close to this value
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