GEN CHEM 2 QUARTER 2 MODULE 1 POST-TEST

The thermodynamic quantity that expresses the degree of disorder in a system is ___________.

• Entropy

• Enthalpy

• Heat flow

• Internal energy

Which one of the following is always positive when a spontaneous process occurs?

• ΔH_universe

• ΔS_universe

• ΔH_surroundings

• ΔS_surroundings

ΔS will be positive for the reaction ____________________.

• CO_2(g) --> CO_2(s)

• 2NO_2(s) --> N₂O_4(g)

• 2H_2(s) + O_2(g) --> 2H₂O_(g)

• BaF_2(s) --> Ba⁺²_(aq) + 2F^-_(aq)

Given the following thermodynamic quantities at 298.15 K (25 ^oC), answer the following question.

The value of for the catalytic hydrogenation of acetylene to ethene, C₂H_2(g) + H_2(g) --> C₂H_4(g) is ____________ J/K.

• -18.6

• +18.6

• +112.0

• -112.0

Which of the following changes is ruled by the tendency of particles to become more disordered?

• Cooling of the hot frying pan

• Dissolving of sugar in water

• The condensation of water vapor to rain

• The reaction of iron with oxygen to produce rust

Given the following thermodynamic quantities at 298.15 K (25 ^oC), answer the following question.

The value of for the oxidation of solid elemental sulfur to gaseous sulfur trioxide, 2S_(s,rhombic) + 3O_2(g) --> 2SO_3(g) is ____________kJ.

• -790.4

• -395.2

• +395.2

• +790.4

Given the following thermodynamic quantities at 298.15 K (25 ^oC), answer the following question.

The value of for the formation of POCl₃ from its constituent elements, P_2(g) + O_2(g) + 3Cl_2(g) --> 2POCl_3(g) is ____________kJ.

• -1109

• +1109

• -606.2

• +606.2

1. For the reaction, C₂H_6(g) --> C₂H_4(g) + H_2(g), ΔH^o=+137 kJ and ΔS^o=120 J/K. This reaction is _______.

• spontaneous at all temperatures

• nonspontaneous at all temperatures

• spontaneous only at high temperatures

• nonspontaneous only at high temperatures

1. A reaction that is not spontaneous at low temperature can become spontaneous at high temperature if ΔH is _______ and ΔS is ________.

• +,+

• -,-

• +,-

• -,+

A reaction that is not spontaneous at low temperature can become spontaneous at high temperature if ΔH is _______ and ΔS is ________.

• +,+

• -,-

• +.-

• -,+