Heat of Formation Practice

Enthalpy of formation is designated with a subscript ___.

What does constituent mean related to heat of formation?

• the compound itself

• a substance that is in its natural state already

• the elements that make up a compound

• the compound is a solid

A substance has a standard heat of formation of 0 kJ/mol. What does this mean?

• the substance has only single bonds in it

• the substance is already in its natural form

• the substance does not need to be formed from constituents

• two of these are correct

To calculate the heat of formation for an overall reaction you will...

• subtract reactants from products

• subtract products from reactants

• subtract bonds formed from bonds broken

• all of these are correct

The subscript of ΔH tells us...

• the type of enthalpy we are measuring

• the conditions we are under

• the magnitude of the heat lost

• none of these are correct

What is the ΔHf of ethane (C2H6)?

• -74.80

• 226.7

• -84.68

• -277.7

What does it mean if ΔHf is a negative value?

• endothermic

• exothermic

• energy is absorbed

• heat is absorbed

What is the ΔHf of liquid water (H2O)?

• -36.23

• 25.9

• -241.8

• -285.8

Calculate the heat of formation for the following reaction under standard conditions:

C(diamond) + O2 (g) --> CO2 (g)

• -391.62

• -395.38

• 395.38

• 394.88