Chapter 10 and 11 Flashcards
Hess’s law
enthalpy change for a chemical or physical reaction depends only on initial and final states
the enthalpy change is independent of the reaction pathway
4 rules for manipulation equations in triangle H notation
1) when equation is flipped the sign on triangle H must be reversed
2) compounds that are on opposite sides of equation can only be cancelled out if they are in the same state
3) if the coefficients of the equation are multiplied or divided the same must be dont to their triangle H
4) compounds that are on the same sides of the equation can only be added together if they are in the same state
steps for manipulating equations in triangle H notation
1) write out net equation if not given
2) manipulate equations in order to yield net equation
- flip
- multiply or divide
3) cancel out compounds on opposite sides that are same state and number
4) add remaining compounds to yield net equation
thing to remember when multiply to manipulate an equation in triangle H notation and example
may have to multiply by a fraction to get the right number
Ex) have: 2H20 need: 3H20
multiply by 2/3
Hess’s law formula
H reaction= the sum of nH products- the sum of nH reactants
standard molar enthalpy of elements in standard states
0
2 options for hess’s law calculations
triangle H (long way)
triangle H dot (short way, standard molar enthalpies)
steps for Hess’s law calculations in triangle H
1) carry out steps for manipulating equations in triangle H notation
2) add the component enthalpy changes to obtain the net enthalpy change
steps for Hess’s law calculations in triangle H dot
1) write out net equation if not given
2) determine unknown
3) manipulate Hess’s law formula to solve for unknown
if H dot of something equals 0 what is it’s n value?
O
exception to Hess’s law calculations in triangle H dot
why and what do to
if net equation has 2 or more elements
since there are no standard enthalpies of formation to plug into formula
do it as you would triangle H
efficiency formula
(energy output/energy input) (100)
What to do if Energy input/output isn’t directly given
use Eout or in= Qcan +Qwater
and expand to m(c)(trianglet) to solve
scientific perspective
research
leads to researching and explaining natural phenomena
technological perspective
technology
concerned with the development and use of machines, instruments, and processes that have a social purpose
ecological perspective
environmental effects
considers relationships between living organisms and the environment
renewable energy source
replenishes itself within 100 years
non renewable energy source
fill in
greenhouse gases
fill in
global warming
fill in
economic perspective
financial
gives on the production, distribution, and consumption of wealth
