Thermodynamics Quiz (Released Questions)

What is the heat of combustion of benzene, C₆H₆, in kJ/g?

• -41.74 kJ/g

• -35.8 kJ/g

• -5.96 kJ/g

• -118 kJ/g

• -387 kJ/g

Define Endothermic

• Energy is absorbed; ΔH is negative; Going from Liquid to Gas, and Gas to Liquid

• Energy is released; ΔH is negative; Going from Solid to Liquid, and Liquid to Gas

• Energy is released; ΔH is positive; Going from Solid to Liquid, and Liquid to Gas

• Energy is absorbed; ΔH is positive; Going from Solid to Liquid, and Liquid to Gas

Is the phase change representing an exothermic or endothermic reaction?

SOLID to LIQUID

• Endothermic

• Exothermic

Define ΔH

• Change in Specific Heat; Heat by one Degree Celsius

• Change in Temperature; the energy we calculate; Degree Celsius

• Change in Enthalpy; the energy/heat we calculate

• Change in Time; time travel

Thermal energy is measurement of what type of molecular energy?

• specific heat

• kinetic energy

• potential energy

• chemical energy

Do molecules generally move faster at 45 C or 106 C?

• 45 C because molecules have more energy than in 106C

• 106 C because molecules have more energy than in 45C

• 106 C because molecules have less energy than in 45C

• 45C because molecules have less energy than in 106 C

When a 21.1-g sample of ethyl alcohol, C₂H₅OH, is burned, how much energy is released as heat? ΔH= -1367kJ/mol

• 0.458 kJ

• 0.627 kJ

• 2.18 kJ

• 627 kJ

• 28,900 kJ

YOU HAVE TIME!

How much energy is needed to raise the temperature of a 20.0g piece of copper from 15.0 degrees Celsius to 25.0 degrees Celsius? (The specific heat of copper is 0.385 J/g C)

• 20 X (25-15) =70 J

• 20 X .385 X (25-15)= 77 J

• 20 X .385 X (15-25)= 62 J

• 20 X .385 X (15-0)= 77 J

The specific heat of a substance is the amount of energy needed to raise the temperature of:

• 1 gram by 1 Kelvin or 1 Celsius

• 1 mole by 1 Kelvin

• 1 gram by 1 degrees Fahrenheit

• 1 mol by 1 Joules

Is the reaction exothermic or endothermic?

H2 + S + O2 -> H2SO4 ΔH = -811.13kJ

• ΔH is negative so it is exothermic

• ΔH is positive so it is exothermic

• ΔH is positive so it is endothermic

• ΔH is negative so it is endothermic