Standard Heat of Formation

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

• -393.5 kJ/mol

• -566.0 kJ/mol

• 566.0 kJ/mol

• -369 kJ/mol

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]

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

• -890.25 kJ/mol

• -604.45 kJ/mol

• -754.15 kJ/mol

• No way to tell

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

NGSS.HS-PS3-1

In an endothermic reaction, heat is ...

• taken in or absorbed
• given out or released 

Tags

NGSS.HS-PS1-4