Lecture 16- Thermodynamics 2 Flashcards
Calorimetry
the measurement of heat transfer using a calorimeter (a device used to determine the amount of heat transferred)
specific heat capacity of water
4.184J/gC
^q
^q=mc^T
- q=heat lost or gained by a substance
- m=mass of that substance
- c=specific heat capacity of that substance
- ^T=temp change of that substance
^q vs. ^H
- ^qrxn= the heat lost or gained in the experiment that took place in the calorimeter
- ^Hrxn= the heat lost or gained in the balanced chemical equation
Hess’s Law
- The overall enthalpy change will be the same if a reaction is carried out in one step or in several steps
- manipulate equations
Standard enthalpy of formation
- a hypothetical value that indicates how much heat would be lost or gained during the formation of one mole of a compound from the most common form of its elements in their standard states
- under standard conditions
- most stable form of any element in its standard state is zero
^Hrxn=sumn^H(products) - sumn^H(reactants)
relating to calorimetry
^q=mc^T
How much was gained/lost?
opposite signs, same number
what is the specific heat?
- manipulate to solve for c
what is the enthalpy change for the formation of 1 mol of
^Hrxn=^q/m and M=m/L
- Use q=mc^T to find q
- Use M=m/L to find m
- and plug into ^Hrxn=^q/m
Write the chemical equation
- write and cross out dissolving
find the heat of reaction ^Hrnx
^Hrxn=^q/m and M=m/L
- Use q=mc^T to find q
- Use M=m/L to find m
- and plug into ^Hrxn=^q/m
Hf equals
Hrxn
Hrxn label
Kj/mol
determine the enthalpy change given multiple equations
Hess’s law
- flip then switch sign
- multiply then multiply
- add values
using standard enthalpy of formation
^Hrxn= sum n ^H (products) - sum n ^H (reactants)
why were humans able to use this element before that one
Humans were able to use elemental copper before they were able to use tin. The Hf for CuO is -156 while the Hf for SnO2 is -581. It takes less energy and is easier to create copper, which is why they discovered and used it first.
write a balanced equation that outlines the reaction used to determine the enthalpy of formation for
use basic elemental states
how much heat is released or absorbed when g of x reacts with excess x as shown in the equation below
grams/1 X moles/grams X ^Hrxn/moles in the equation
