Chemistry 11 Chapter 14

101.3 J

1 L.atm = ____ J

1 cal = ___ J 1 Cal = ____ kcal = ____ cal

1 cal = 4.185 J 1 Cal = 1 kcal = 1,000 cal

The 7 steps for using method 5 (bond energy) are as follows:

1: draw the Lewis structure for all molecules 2: look up the bond energies of the bonds in question 3: multiply the bond energies by the number of bonds broken 4: add up all of the bond energies of the broken bonds 5: multiply the bond energies by the number of bonds formed 6: add up all of the formed bond energies 7: subtract the bond energy of the products from the bond energy of the reactants

As part of method 4 (standard enthalpy of formation) for obtaining heat of reaction, what are the conventional definitions of standard states for a compound? What about for a gas?

For a compound: for a gas, pressure is exactly 1 atm, for a solution concentration is exactly 1 M, for a liquid/solid it's a pure substance For an element: the form in which it exists at 1 atm and 25 degress C; the heat of formation for elements is zero.

work = P x A x delta h or work = P x delta V but work is pretty much always negative so: w = -P x delta V

For work involving gases, work = _____.

The third method for obtaining heat of reaction (q) is ______. This law states that, in going from a particular set of reactants to a particular set of products, the change in enthalpy is different/the same whether the reaction takes place in one step or in a _____ of steps

Hess' Law; change in enthalpy is the same; series of steps

Identify the system, surroundings, and give the direction of energy transfer: Methane is burning in a Bunsen burner in a lab

System - methane and oxygen to produce carbon dioxide and water; Surroundings - everything else around it; Direction of energy transfer - energy transfers from the system to the surroundings (exothermic)

delta U = q + w q represents heat w represents work

To change the internal energy of a system (as it relates the first law of thermodynamics), _______.

Identify the system, surroundings, and give the direction of energy transfer: Water drops sitting on your skin after swimming, evaporate

a)System - water drops; Surroundings - everything else around it; Direction of energy transfer - energy transfers from the surroundings (your body) to the system (water drops) (endothermic)

The fifth method for obtaining heat of reaction is _____. In this method, the _____ is the amount of energy required to _____.. This differs from method 4 in that _____

bond energy; the bond energy is the amount of energy required to break apart a mole of molecules into its component atoms in gaseous state; differs in that we do energy of reactants - energy of products

The formula for enthalpy is _____ where all terms are _____ and ______.

delta H = delta U + delta PV; state functions; delta H = H products - H reactants

At constant pressure, the formula for enthalpy can be written as ____ and, therefore, heat of reaction (which is not a state function) at constant pressure can be obtained from the change of enthalpy of the reaction (which is a state function)

delta H = q sub p

Endo or Exo? Ice cream (the system) melts

endo

Endo or Exo? The ice (the system) gets warmer when you touch it

endo

Endo or Exo? Water (the system) boils in a kettle being heated on a stove

endo

In endothermic/exothermic reactions, heat flows into the system. The system ____ energy from the surroundings.

endothermic reactions, heat flows into the system; the system absorbs energy from the surroundings

kinetic energy

energy due to motion of the object and depends on the mass of the object and its velocity

potential energy

energy due to position or composition

energy is/is not a state function while work and heat are/are not state functions.

energy is; work and heat are not

As part of method 4 (standard enthalpy of formation) for obtaining heat of reaction, we do enthalpy of formation of ______ - enthalpy of formation of ____. Elements in their standard states are not included in the equation because heat of formation of an element in its standard state is __.

enthalpy of formation of products - enthalpy of formation of reactants; heat of formation of an element in its standard state is 0

Endo or Exo? Water vapor (the system) condenses on a cold pipe

exo

Endo or Exo? Your hand (the system) gets cold when you touch ice

exo

The freezing of water is an exo/endo process

exothermic

In endothermic/exothermic reactions, heat flows out of the system. The system _____ heat to the surroundings. Energy gained by the surroundings must be _____ to/than the energy lost by the system.

exothermic reactions, heat flows out of the system. The system releases heat to the surroundings. Energy gained by the surroundings must be equal to the energy lost by the system

There are ___ methods of obtaining the heat of reaction (q) and they are:

five; 1: calculating the q for the given amounts from the delta H per mole of the reaction 2: Calorimetry (at constant pressure using a Coffee Cup Calorimeter; at constant volume using a Bomb Calorimeter) 3: Hess' Law (calculating q from delta H of a series of reactions) 4: Standard Enthalpies of Formation (tabulated delta H^osubf) 5: Bond Energies (tabulated values)

work

force acting over a distance

The two main issues with calculating heat of reaction are: ____ and _____. Therefore, a ______ for heat of reaction measurements is necessary

heat is not a state function different labs can obtain different measurements for heat of reaction for the same reaction at different conditions, such as pressure, temperature, and the way the reaction is carried out state function

surroundings

include everything else in the universe

possible units for energy include _____, _____, _____, and _____

kg.m^2/s^2 or J, L.atm, Calories, kilocalories aka nutritional calories

The _____ is often called the first law of thermodynamics

law of conservation of energy

system

part of the universe on which we wish to focus attention

When talking about internal energy/the first law of thermodynamics, the sign reflects the system's _______; if the system does work on surroundings then w is positive/negative; if the surroundings do work on the system then w is negative/positive

point of view; if system does work on surroundings w is negative, but if surroundings do work on system then w is positive

In coffee-cup calorimetry, there is a fixed ______.

pressure

State Function

property that does not depend in any way on the system's past or future (only depends on present state)

With Calorimetry (q at constant pressure), the formula is ______ or ____ or _____.

q sub p = m x c sub cp x delta T OR q sub p = n x C sub p x delta T OR q sub p = c sub p x delta T m = mass (g) n = moles C sub p is the molar (sometimes total) heat capacity (in J/celsius.mol) (just J/celsius if total heat capacity) aka the energy required to raise the temperature of one mol of a substance by one degree C delta T = change in temp (C or K) c sub cp is the specific heat capacity (in J/Celsius.g) aka the energy required to raise the temperature of one gram of a substance by one degree Celsius

The fourth method for obtaining heat of reaction (q) is _____. In this method, the change in enthalpy that accompanies the formation of _____ mole(s) of a compound from its _____ with all substances in their _____.

standard enthalpy of formation; one mole; from its elements; in their natural state

energy

the ability to do work or produce heat

chemical energy

the energy stored in chemical bonds within molecules or ions; can be released or absorbed as heat during chemical reactions

When talking about internal energy/first law of thermodynamics, the _____ reflects the system's point of view; an endothermic process has a negative/positive q, while an exothermic process has a negative/positive q

the sign reflects the system's point of view; endo has positive q, exo has negative q

thermochemistry

the study of heat transfer in chemical reactions

Internal energy (U) of a system is the sum of ______.

the sum of the kinetic and potential energies of all the "particles" in the system

Heat involves the ____ of ____ between two objects due to a temperature difference

transfer of energy

In bomb calorimetry, there is a fixed ______.

volume

In calorimetry, if the reactants at the same temperature are mixed and resulting solution gets colder/warmer, this means the reaction taking place is exothermic; an endothermic/exothermic reaction cools the solution

warmer (exo), cooler (endo)

Heat of a reaction (which is/is not a state function) at constant volume can be obtained from the change of the internal energy of the reaction (which is/is not a state function)

which is not; which is

Work = Force x Distance work = Mass (kg) x Acceleration (m/s^2) x Distance (m)

work = ____ x _____ work = ____ x ____ x ____