Chapter 6 Chemistry Test Study Guide
Qreaction
-Qsolution=?
DeltaE system=
-deltaE of the surroundings
q of the system
-q surroundings
standard enthalpy of formation for a pure element in its standard state
0
-467692.3077 J/mol
0.158 g Mg reacted with enough HCl (aq) to form 100 mL solution in a coffee cup calorimeter. Temperature changed from 25.6 degrees Celsius to 32.8 degrees Celsius. Specific heat of water is 4.18 J/gXdegrees Celsius. Density of water is 1.01 g/mL. Find deltaH of the reaction.
-5.761x10^3 kJ/mol
1 g of sucrose (C12H22O11) is undergoing combustion in a bomb calorimeter. Temperature changed from 24.92 degrees Celsius to 28.33 degrees Celsius. Find the change of energy for the reaction in kJ/mole given that Ccal is 4.90 KJ/degrees Celsius
3.60x10^6 J
1 kWh = J?
If deltaH=+/-X if deltaH=+/-2X
1 mole of 2 reaction 2 mole of 2 reaction
q
=(m)(Cs)(DeltaT)
W
=PxDeltaV =FxD
DeltaE
=q+w =q+PxDeltaV
deltaH
? of a chemical reaction is the amount of heat absorbed (endothermic) or released (exothermic) in a chemical reaction
-1.24 × 103 kJ/mol
A 35.6 g sample of ethanol (C2H5OH) is burned in a bomb calorimeter, according to the following reaction. If the temperature rose from 35.0 to 76.0°C and the heat capacity of the calorimeter is 23.3 kJ/°C, what is the value of DH°rxn? The molar mass of ethanol is 46.07 g/mol. C2H5OH(l) + 3 O2(g) → 2 CO2(g) + 3 H2O(g) H°rxn = ? +9.55 × 103 kJ/mol +1.24 × 103 kJ/mol -8.09 × 103 kJ/mol -1.24 × 103 kJ/mol -9.55 × 103 kJ/mol
-3.20 × 103 kJ/mol
A 4.98 g sample of aniline (C6H5NH2, molar mass = 93.13 g/mol) was combusted in a bomb calorimeter with a heat capacity of 4.25 kJ/°C. If the temperature rose from 29.5°C to 69.8°C, determine the value of ΔE°comb for aniline. -1.71 × 103 kJ/mol -7.81 × 103 kJ/mol +1.71 × 103 kJ/mol +7.81 × 103 kJ/mol -3.20 × 103 kJ/mol
The temperature of the surroundings decreases and the sign on q is positive.
A cold piece of steel (the system) is dropped into a beaker of water (the surroundings) that is 25°C warmer than the piece of steel. Which statement below is true for the change that occurs once the piece of steel is dropped into the beaker of water? The value q in the answer choices below are relative to the system. The temperature of the surroundings decreases and the sign on q is negative. The temperature of the surroundings decreases and the sign on q is positive. The temperature of the surroundings increases and the sign on q is negative. The temperature of the system decreases and the sign on q is positive.
-6.132X10^5 kJ
A gas tank contains 13.2 kg of propane. Calculate the heat (in kJ) released when all the propane int he tank is burned. One mole of propane produes -2044 kJ of heat.
-2277 J
A long cylinder is packed with potatoes. Potatoes are fired. The work done is 855 J on the potatoes and produced 1422 J of heat. What is the change in energy for this process? (The cylinder is the system)
53.7075 J
A penny is in the snow at a temperature of -8 degrees Celsius. The penny has a mass of 3.10 grams. The specific heat of copper is 0.385 J/g times degrees Celsius. How much heat is absorbed by the penny as it warms up to 37 degrees Celsius?
Exothermic
Chemical Reaction in which energy is primarily given off in the form of heat
ΔH2−ΔH1
Consider the reactions: A→2B ΔH1 A→3C ΔH2 What is ΔH for the reaction 2B→3C? 2× (ΔH1+ΔH2) ΔH2−ΔH1 ΔH1+ΔH2 ΔH1−ΔH2
the quantity of heat required to change a system's temperature by 1°C
Define heat capacity. the quantity of heat required to change a system's temperature by 1°C the quantity of heat required to raise the temperature of 1 g of a substance by 1°F the quantity of heat required to lower the temperature of 1 mole of a substance by 1°C the quantity of heat required to lower the temperature of 1 gram of a substance by 1°C the quantity of heat required to lower the temperature of 1 liter of a substance by 1°C
the quantity of heat required to raise the temperature of 1 mole of a substance by 1°C
Define molar heat capacity.
the quantity of heat required to raise the temperature of 1 mole of a substance by 1°C
Define molar heat capacity. the quantity of heat required to change a system's temperature by 1°C the quantity of heat required to raise the temperature of 1 gram of a substance by 1°C the quantity of heat required to lower the temperature of 1 g of a substance by 1°F the quantity of heat required to raise the temperature of 1 mole of a substance by 1°C the quantity of heat required to lower the temperature of 1 liter of a substance by 1°C
the quantity of heat required to raise the temperature of 1 gram of a substance by 1°C
Define specific heat capacity. the quantity of heat required to lower the temperature of 1 mole of a substance by 1°C the quantity of heat required to change a system's temperature by 1°C the quantity of heat required to lower the temperature of 1 gram of a substance by 1°F the quantity of heat required to lower the temperature of 1 liter of a substance by 1°C the quantity of heat required to raise the temperature of 1 gram of a substance by 1°C
Law of Conservation of Energy
Energy cannot be created or destroyed, but it can be converted from one form to another
kinetic energy
Energy that is associated with the motion of an object is called?
-104.7kJ
Find the deltaH of the reaction of the following: 3C(s)+4H2(g)=C3H8(g) Given: (1) C3H8(g)+5O2(g)=3CO2(g)+4H2O(g) deltaH=-2043kJ (2) C(s)+O2(g)=CO2(g) deltaH=-393.5kJ (3) 2H2(g)+O2(g)=2H2O(g) deltaH=-483.6kJ
deltaH=+157.6 kJ
Find the deltaH of the reaction of the following: N2O (g)+NO2 (g)=3NO(g) Given: (1) 2NO (g)+O2 (g)=2NO2 (g) delta H=-113.1 KJ (2) N2 (g)+O2(g)=2 NO (g) delta H=182.6 kJ (3) 2N2O (g)=2No (g)+O2 (g) delta H=-163.2 kJ
The system lost heat and did work on the surroundings.
For a certain process, q and w are both negative. What does this mean?
The system lost heat and did work on the surroundings.
For a certain process, q and w are both negative. Which description below best describes what happened during the process? View Available Hint(s) The system gained heat and the surroundings did work on the system. The surroundings gained heat and did work on the system. The system lost heat and did work on the surroundings. The surroundings lost heat and the system did work on the surroundings.
-w > +q
For ΔEsys to always be -, what must be true? q = w +w > -q +q > -w -w > +q
J/g °C
Give the units of specific heat capacity. gmole °C g/°C J/g °C Jmole °C J/°C
+ ΔH and +ΔE
Given w = 0, an endothermic reaction has the following. + ΔH and +ΔE - ΔH and +ΔE +ΔH and -ΔE - ΔH and -ΔE
from objects of higher temperature to objects of lower temperature
How does energy flow?
w=−PΔV
How is pressure volume work calculated? w=−PΔV w=P+V w=PΔV w=P−ΔV
Until thermal equilibrium is reached (both objects temperature is equal)
How long will heat exchange continue?
1.52 x 103 kJ
How much energy is evolved during the formation of 197 g of Fe, according to the reaction below? Fe2O3(s) + 2 Al(s) → Al2O3(s) + 2 Fe(s) ΔH°rxn = -852 kJ 3.02 x 103 kJ 964 kJ 482 kJ 1.52 x 103 kJ 8.40 x 103 kJ
deltaH of the reaction must be multiplied by the same factor Example: A+B=C 4A+4B=4C
If a chemical reaction is multiplied by a factor the what happens to the deltaH of the reaction?
0
If the work is done under constant volume, then what is deltaV?
two times
If you have one mole of two reactants whatever deltaH is released/absorbed, the delta H released/absorbed will be how many times?
-177.275 J
If you inflate a balloon from a volume of 0.100 L to 1.85 L against an external pressure of 1 atm. How much work is done in joules by the system? 1 Lxatm=101.3 Joules
-94.6 kJ
In the presence of excess oxygen, methane gas burns in a constant-pressure system to yield carbon dioxide and water: CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) ΔH = -890.0 kJ Calculate the value of q (kJ) in this exothermic reaction when 1.70 g of methane is combusted at constant pressure. -94.6 kJ 0.0306 kJ -9.46 × 104 kJ 32.7 kJ -0.0106 kJ
Exothermic
Is a hot cup of coffee (system) cools on a countertop endothermic or exothermic?
Yes
Is enthalpy a state function?
Yes
Is internal energy a state function?
Exothermic
Is the chemical reaction in a "hot pack" often used to treat sore muscles endothermic or exothermic?
Exothermic
Is the combustion of butane endothermic or exothermic?
Endothermic
Is the evaporation of alcohol endothermic or exothermic?
Exothermic
Is the freezing of water endothermic or exothermic?
Units of Energy
Joules (J) kilowatt hour (kWh) Calorie (Cal) calorie (cal)
1/2 kg(m/s)^2 (m=mass) (v=velocity)
KE and Joule
coffee-cup calorimetry
Occurs at constant pressure and measures delta H for a reaction
The measure of a substances ability to absorb heat
Specific heat (Cs)
The surrounding is doing work on the system(energy flows from the surroundings to the system)
System is gaining deltaE (E final is greater than E initial)(deltaE is positive)
Joule
The amount of energy needed to move a mass of one kg at a velocity of one m/s
Enthalpy (H) or heat of a reaction
The heat evolved in a chemical reaction at constant pressure. The heat content of a system.
None of the above statements are true.
Two aqueous solutions are both at room temperature and are then mixed in a coffee cup calorimeter. The reaction causes the temperature of the resulting solution to fall below room temperature. Which of the following statements is TRUE? Energy is leaving the system during reaction. This type of experiment will provide data to calculate ΔErxn. The products have a lower potential energy than the reactants. The reaction is exothermic. None of the above statements are true.
kinetic and potential energy
Two basic types of energy
-59 kJ
Two solutions, initially at 24.60°C, are mixed in a coffee cup calorimeter (Ccal = 15.5 J/°C). When a 100.0 mL volume of 0.100 M AgNO3 solution is mixed with a 100.0 mL sample of 0.200 M NaCl solution, the temperature in the calorimeter rises to 25.30°C. Determine the DH°rxn for the reaction as written below. Assume that the density and heat capacity of the solutions is the same as that of water. NaCl(aq) + AgNO3(aq) → AgCl(s) + NaNO3(aq) DH°rxn = ? -59 kJ -16 kJ -250 kJ -35 kJ -140 kJ
Constant volume
Under what conditions is the change in internal energy, ΔE rxn , equal to the heat evolved in a reaction? View Available Hint(s) Constant pressure Constant volume Constant temperature ΔE rxn is never equal to the heat evolved in a reaction.
-791.4 kJ
Use the standard reaction enthalpies given below to determine ΔH°rxn for the following reaction: 2 S(s) + 3 O2(g) → 2 SO3(g) ΔH°rxn = ? Given: SO2(g) → S(s) + O2(g) ΔH°rxn = +296.8 kJ 2 SO2(g) + O2(g) → 2 SO3(g) ΔH°rxn = -197.8 kJ -791.4 kJ -293.0 kJ -494.6 kJ -692.4 kJ 1583 kJ
-1835 kJ
Use the standard reaction enthalpies given below to determine ΔH°rxn for the following reaction: P4(g) + 10 Cl2(g) → 4PCl5(s) ΔH°rxn = ? Given: PCl5(s) → PCl3(g) + Cl2(g) ΔH°rxn = +157 kJ P4(g) + 6 Cl2(g) → 4 PCl3(g) ΔH°rxn = -1207 kJ -1364 kJ -1786 kJ -1835 kJ -1050. kJ -2100. kJ
Both are positive
What are the signs for deltaE and deltaH if w=0 in an endothermic reaction?
The system ( the reactant) is giving deltaE to the surroundings
What does it mean if E initial is larger than E final (delta E is negative)
1000 calories 4184 Joules
What does one Calorie equal in calories and joules?
deltaE
What does the heat of a system equal at constant volume (Qv)?
The final deltaH of the reaction is the sum of all the steps. Example: A=B deltaH B=C deltaH2 A=C deltaH+deltaH2=deltaH of the reaction
What happens to delta H if a chemical reaction is made up of multiple steps?
The sign of deltaH will be reversed Example: A+B=C deltaH=-10kJ (exothermic) C=A+B delta H=+10 kJ(endothermic)
What happens to delta H if a reaction is reversed?
depends on initial and final states only. energy does not depend on how the system arrives at the final state
What is a state function
Pressure-volume work is work that happens when force is procured by a volume change pushing against an external pressure.
What is pressure-volume work?
joule
What is the SI unit of energy? bar calorie joule kilowatt-hour
deltaE+Pressure times deltaV
What is the change in enthalpy formula (deltaH)?
MsolxCs(solution)xdeltaT(solution)
What is the equation for the Qsolution?
deltaE=Qv
What is the formula for change of energy under constant volume?
deltaE=q+w
What is the formula for change of energy?
DeltaE=work+heat DeltaE=w+q
What is the formula for deltaE
E+PV
What is the formula for enthalpy (H) at constant pressure?
C=Q/delta T
What is the formula for heat capacity?
q=(m)(Cs)(deltaT)
What is the formula for heat when you are given mass and the specific heat of a substance?
q=cxdeltaT c=constant of proportionality or heat capacity
What is the formula for heat?
deltaE=q+w deltaErxn=Qrxn deltaErxn=Qrxn/mole
What is the formula for measuring deltaE in a bomb calorimeter?
q=(Cs)(deltaT)(m) m=mass in grams delta T=degree Celsius or Kelvin Cs=J/degree Celsius times gram Cs=q/deltaT times m
What is the formula for specific heat (Cs)
deltaE=Efinal-Einitial
What is the formula for the change of energy?
Qcal=Ccal*deltaT Qcal=-Qrxn
What is the formula to determine the change in energy in a bomb calorimeter?
deltaH=Qp
What is the formula to measure deltaH of a reaction at constant pressure in a calorimetry?
deltaHrxn/1 mole of reactant
What is the heat of reaction per mole?
J/degrees Celsius
What is the unit for heat capacity?
0
What is the value of work in a bomb calorimeter?
Extensive property. It depends on the quantity of the matter.
What kind of property is enthalpy?
Pressure
What part of a reaction is constant in a calorimetry?
Negative on both
What signs on q and w represent a system that is doing work on the surroundings, as well as losing heat to the surroundings?
The system is losing 115 J, while the surroundings are gaining 115 J.
Which of the following is TRUE if ΔEsys = - 115 J? Both the system and the surroundings are gaining 115 J. The system is losing 115 J, while the surroundings are gaining 115 J. Both the system and the surroundings are losing 115 J. The system is gaining 115 J, while the surroundings are losing 115 J. None of the above are true.
for a solid, it is 25°F
Which of the following is not a standard state? for a gas, it is 1 atm for a liquid, it is 25°C for a liquid, it is 1 atm for a solid, it is 25°F for a solution, it is 1 M
for a liquid, it is 25°F
Which of the following is not a standard state? for a solution, it is 1 M for a solid, it is 25°C for a liquid, it is 25°F for a liquid, it is 1 atm for a solid, it is 1 atm
the vaporization of rubbing alcohol
Which of the following processes is endothermic? the vaporization of rubbing alcohol the chemical reaction in a "hot pack" often used to treat sore muscles the freezing of water a hot cup of coffee (system) cools on a countertop the combustion of butane
a candle flame
Which of the following processes is exothermic? the chemical reaction in a "cold pack" often used to treat injuries baking bread a candle flame the vaporization of water None of the above are exothermic.
q = -, w = -
Which of the following signs on q and w represent a system that is doing work on the surroundings, as well as losing heat to the surroundings? q = -, w = - q = -, w = + q = +, w = + q = +, w = - None of these represent the system referenced above.
Heat transfers from the block to the water. q metal- q water
You have a metal block at 55 degrees Celsius, that you put into a container of water at 25 degrees Celsius. What happens to the heat? What is the formula to determine the heat transferred?
Standard state for a substance in solution
a concentration of exactly 1 M
system
an object of chemical reaction under study
DeltaT
change in temperature between two objects
Qp=Qrxn
deltaHrxn at constant pressure=?
+deltaH
endothermic reaction
thermal energy
energy associated with the temperature of an object
Potential Energy
energy due to position or composition Example: chemical, nuclear
Kinetic energy
energy of motion Example: electric, thermal
-deltaH
exothermic reation
products
final energy
W=FxD W=(P)(deltaV)
formula for work
therm
heat
two
how many kinds of energy is there?
reactants
initial energy
kinetic+potential energy
internal energy of a system
1/2mv^2
kinetic energy
first law of thermodynamics
law of conservation of energy total earth's energy is constant energy cannot be created or destroyed there is no perpetual motion machine
thermochemistry
means relationship between a chemical reaction and heat/energy
energy flows out of the system
negative deltaE
system loses thermal energy
negative q
work done by the system
negative w
Bomb calorimetry
occurs at constant volume and measures delta E for a reaction
energy flows into the system
positive deltaE
system gains thermal energy
positive q
work done on the system
positive w
DeltaT
q is proportional to what?
Energy
the ability to do work
chemical energy
the energy associated with the relative positions of electrons and nuclei in atoms and molecules
Internal energy
the energy of a system (kinetic and potential)
surroundings
the environment around the system
Standard State for a gas
the pure gas at a pressure of exactly 1 atm.
Standard state for a liquid or solid
the pure substance in its most stable form at a pressure of 1 atm and at the temperature of interest (often taken to be 25 degrees Celsius)
bomb calorimeter
using what can you determine the change of heat of a system at constant volume?
4.184 Joules
what does one calorie equal?
elevation
what is one example of a state function? a. elevation b. distance
Standard enthalpy of formation for a pure compound
when 1 mol of the compound forms from its constituent elements in the standard states
