Week 2Thermochemistry

Question 1

What does a bomb calorimeter measure

What is the 𝝙Erxn equation

Answer 1

𝝙Erxn=qxn at CONSTANT VOLUME
Heat of reaction has opposite sign from heat of calorimeter
qcal=-qrxn
𝝙Erxn=-Ccal𝝙T

Question 2

What does Coffee cup calorimeter measure

What is the final equation of 𝝙H

Answer 2

𝝙Hrxn=qrxn at constant pressure
qrxn=-qsoln
𝝙Hrxn=-msolnC(s or sln)𝝙T

Question 3

Hess’ Law

Answer 3

𝝙Hrxn is the sum of enthalpy change of each step of a stepwise reaction
ie. 𝝙Hrxn= 𝝙H1+ 𝝙H2 + etc

Question 4

Elements in Standard States

Answer 4

PURE SUBSTANCES in its most stable state
1 atm
25 degrees celsius

Question 5

Compounds in standard states

Answer 5

Gases: Pressure of pure gas at 1 atm
Liquids or solids:
Pure substances in its most stable state
1 atm
25 degrees celcius
Solutions: 1 M

Question 6

°Standard enthalpies (has the degree symbols) and standard enthapy of formation

Answer 6

Standard enthalpy: all reactants and products are at standard state
Formation: Hf °
Pure compounds: 1 mol forms constituent elements in their standard states
Pure elements: The constituent element of an element is itself
Standard enthalpy of formation is 0!!!!

Question 7

How do you find/Equation for finding standard enthalpy of an equation

Answer 7

using the standard of formation of products and reactants
Equation= (sum of standard enthalpies and coefficients of products-(sum of standard enthalpies and coefficients of reactants)

Question 8

Formation: 𝝙H when a bond is formed/Break
What is the equation

Answer 8

Break=+
Form=-
𝝙Hrxn= sum of bonds broken (positve)+ sum of bonds formed (negative)

Question 9

Lattice Energy

Answer 9

Heat released when forming 1 mole of ionic solid from its constituent gaseous ions
going grom gases to solids
Nagative standard of enthalpy change (exothermic)

Question 10

Colulombs Law, what is the effect of ion size on lattice energy

Answer 10

E=(q1xq2)/r
E= lattice energy
r= interionic distance
Smaller r, higher lattice energy