Chapter 6 (section 9)

Question 1

What is the standard state for a gas?

Answer 1

Pure gas at a pressure of exactly 1 bar.

Question 2

What is the standard state for a liquid or solid?

Answer 2

The pure substance in its most stable form at a pressure of 1 bar and at the temperature of interest (usually 298 k)

Question 3

What is the standard state for a substance in solution?

Answer 3

A concentration of exactly 1 mol/L

Question 4

What is the standard enthalpy change (ΔᵣHº)?

Answer 4

The change in enthalpy for a process when all reactants and products are in their standard states.

Question 5

What does the º on the ∆ᵣHº indicate?

Answer 5

It indicates standard state. All the products and reactants are in their standard states

Question 6

What is the standard enthalpy of formation ΔfHº for a pure compound?

Answer 6

The chnage in enthalpy when 1 mol of the compound forms from its ocnstituent elements in their standard states

Question 7

What is the standard enthalpy of formation ΔfHº for a pure element in its standard state?

Answer 7

0 kJ/mol

Question 8

Define standard heat of formation

Answer 8

The change in enthalpy when 1 mol of a compound forms from its constituent elements in their standard states.

Question 9

standard enthalpy of formation is also called …?

Answer 9

standard heat of formation

Question 10

The _____ of standard enthalpy of formation corresponds to the decomposition of a compound into its elements in their standard states.

Answer 10

negative

Question 11

ΔᵣHº = ∑ np ∆fHº (products) - ∑ nr ∆fHº (recatants)

What is this equation in words?

Answer 11

To calculate ΔᵣHº, subtract the enthalpies of formation of the reactants multiplied by their stoichiometric coefficients from the enthalpies of formation of the products multiplied by their stoichimetric coeffecients