Ch 6 - Everything Enthalpy

Question 1

Rule 1

Answer 1

If a chemical equation is multiplied by some factor then the delta H is also multiplied by the same factor.

A + 2B -> C at delta H
2A + 4B -> 2C at 2(delta H)

Question 2

Rule 2

Answer 2

If a chemical equation is reversed then the delta H changes sign.

A+ 2B -> C at delta H
C -> A + 2B at -(delta H)

Question 3

Rule 3

Answer 3

Hess Law

if a chemical equation can be expressed as the sum of a series of steps, then delta Hrxn for the overall equation is the sum of the heats of reactions for each step.

A + 2B -> C
C -> 2D

then A + 2B -> 2D

Question 4

Standard State

Answer 4

how something is found in nature at exactly 1atm of pressure(Gasses) and 25 C(solid and liquid)

Question 5

Standard State: AQ Soln

Answer 5

how something is at exactly 1M solution.

Question 6

Standard Enthalpy Change

Answer 6

the change of enthalpy for a process when all reactants and products are in their standard states. The degree sign indicates standard states.

Question 7

Standard Enthalpy of Formation(deltaH degree f)

Answer 7

Pure compound: the change in enthalpy when one mole of the compound forms from its constituent elements in their standard states.

Pure element: The delta H degree f is ALWAYS 0.

Question 8

Standard Heat of Formation

Answer 8

another name for the Standard Enthalpy of Formation(deltaH degree f)

Always written to create 1 mol of a compound.

In kJ/mol.

Question 9

Standard Enthalpies of Formation Formula

Answer 9

deltaHrxn = [(Sum of Products)(their coefficients)] - [(sum of reactants)(their coefficients)