Heats of Formation Quiz 2

A reaction is performed in a beaker with a temperature probe recording the temperature changes of the reaction.  If the temperature began at 15.0 degrees Celsius and ended at 27.5 degrees Celsius.  If the reaction is our system, is the system endothermic or exothermic?

• Exothermic
• Endothermic

Tags

NGSS.HS-PS1-4

Enthalpy is energy absorbed or relased during a chemical reaction as

• light.
• heat.
• sound.
• pressure.

Tags

NGSS.HS-PS1-4

In an endothermic reaction, the sum of the heats of formation of the products are____than the sum of the heats of formation of the reactants. Hint: is ΔH + or -? This about how you calculate ΔH

• less than
• greater than
• equal to

Tags

NGSS.HS-PS1-4

Calculate the change in enthalpy  $\Delta H$  for the following reaction:
 $2CO\ +\ O_{2_{\ _{ }}^{ }}\longrightarrow\ 2CO_{2_{ }}$  
Use your heats of formation table from your worksheet

• -393.5 kJ/mol

• -566.0 kJ/mol

• 566.0 kJ/mol

• -369 kJ/mol

Tags

NGSS.HS-PS1-4

Which one of the following expressions is the correct way to calculate standard enthalpy change for the combustion of propane?

C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(l)

Use your heats of formation table for reference.

• [103.85 + (5 × 286)] – [-393.5 + -285.8]

• [-103.85 + 0] + [(3 x -393.5) + (4 x -285.8)]

• [-103.85 + 0] – [(3 x -393.5) + (4 x -285.8)]

• [(3 x -393.5) + (4 x -285.8)] + [-103.85 + 0]

Tags

NGSS.HS-PS1-4

What is the heat of formation for 6 moles of ethanol? Use your heats of formation table for reference.

• -1666.2 kJ/mol

• -277.7 kJ/mol

• 52.3 kJ/mol

• Only able to calculate in a reaction

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

Calculate $\Delta H$  using heats of formation for the combustion of methane:
 $CH_4\left(g\right)\ +\ 2O_2\left(g\right)\ \rightarrow\ CO_2\left(g\right)\ +2H_2O\left(l\right)$  
Use your heats of formation table for reference.

• -890.25 kJ/mol

• -604.45 kJ/mol

• -754.15 kJ/mol

• No way to tell

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

What is the difference between calculating $\Delta H$   with bond energies versus with heats of formation?

• Bond energies are averages based on multiple scenarios of breaking bonds, heats of formation is the energy required to form a specific molecule from its elemental forms.

• Heats of formation are averages based on multiple scenarios of breaking bonds, bond energies is the energy required to form a specific molecule from its elemental forms.

• Bond energies are calculated using only lewis dot structures, but heats of formation requires a reference table

• Heats of formation helps calculate enthalpy, while bond energies helps calculate entropy

Tags

NGSS.HS-PS1-4

What is the heat of formation for 8 moles of ammonia? Use your heats of formation table for reference.

• -369.52 kJ/mol

• -46.19 kJ/mol

• -92.38 kJ/mol

• -102.4 kJ/mol

Tags

NGSS.HS-PS1-4

In an endothermic reaction, heat is ...

• taken in or absorbed
• given out or released 

Tags

NGSS.HS-PS1-4