CHEM 1B Lecture Notes - Lecture 2: Heat Capacity, Calorimetry, Jmol

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salmonmosquito29

7 Sep 2016

School

UC-Irvine

Department

Chemistry

Course

CHEM 1B

Professor

Ramesh D Arasasingham

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Document Summary

The changes that substance undergo can be of two kinds. Physical change is any change that takes place where the composition of the substance remains the same (no change). Ice (h2o) s liquid water (h2o) l water vapor (h2o) g. H2o (l) ---> h2o (g) (+44 kj/mol) Attractive forces between molecules are being broken by the energy (heat) supplied. Chemical change is any change that takes place when the composition of the substance change. New substances are formed, and the chemical properties of the new substance are different from the original substance. H2o (l) ------electrolysis (energy)-------> h2(s) + o2 (s) (+265 kj/mol) H-h and o--o (new bonds are formed so energy is released) (energy is supplied so bonds are broken) Regardless of the type change, all changes are accompanied by changes in energy. Energy is the capacity to do work or to transfer heat. Energy can be kinetic energy or potential energy.

Related Questions

I do not understand any of this, please help.

1- The molar heat capacity of silver is 25.35 J/molâ âC. How much energy would it take to raise the temperature of 8.20 g of silver by 14.5 âC?

Express your answer with the appropriate units.

_____________

Part A

Calculate the enthalpy of the reaction

2NO(g)+O2(g)â2NO2(g)

given the following reactions and enthalpies of formation:

12N2(g)+O2(g)âNO2(g), ÎHâA=33.2 kJ

12N2(g)+12O2(g)âNO(g), ÎHâB=90.2 kJ

Express your answer with the appropriate units.

2- A total of 2.00 mol of a compound is allowed to react with water in a foam coffee cup and the reaction produces 196 g of solution. The reaction caused the temperature of the solution to rise from 21.00 to 24.70 âC. What is the enthalpy of this reaction? Assume that no heat is lost to the surroundings or to the coffee cup itself and that the specific heat of the solution is the same as that of pure water.

Enter your answer in kilojoules per mole of compound to three significant figures.

_________

3- A volume of 110. mL of H2O is initially at room temperature (22.00 âC). A chilled steel rod at 2.00 âCis placed in the water. If the final temperature of the system is 21.00 âC , what is the mass of the steel bar?

Use the following values:

specific heat of water = 4.18 J/(gâ âC)

specific heat of steel = 0.452 J/(gâ âC)

Express your answer to three significant figures and include the appropriate units.

Part B

The specific heat of water is 4.18 J/(gâ âC). Calculate the molar heat capacity of water.

Express your answer to three significant figures and include the appropriate units.

______-

4- What is the enthalpy for the following reaction?

overall: N2O4â2NO2

Express your answer numerically in kilojoules per mole.

____________

Part B

Calculate the enthalpy of the reaction

4B(s)+3O2(g)â2B2O3(s)

given the following pertinent information:

B2O3(s)+3H2O(g)â3O2(g)+B2H6(g), ÎHâA=+2035 kJ

2B(s)+3H2(g)âB2H6(g), ÎHâB=+36 kJ

H2(g)+12O2(g)âH2O(l), ÎHâC=â285 kJ

H2O(l)âH2O(g), ÎHâD=+44 kJ

Express your answer with the appropriate units.

_____________

5- What is the balanced chemical equation for the reaction used to calculate ÎHâf of MgCO3(s)?

If fractional coefficients are required, enter them as a fraction (i.e. 1/3). Indicate the physical states using the abbreviation (s), (l), or (g) for solid, liquid, or gas, respectively without indicating allotropes. Use (aq) for aqueous solution.

Express your answer as a chemical equation.

__________

6- Part A

Determine the enthalpy for this reaction:

Ca(OH)2(s)+CO2(g)âCaCO3(s)+H2O(l)

Express your answer in kilojoules per mole to one decimal place.

_______

Part B

Consider the reaction

Ca(OH)2(s)âCaO(s)+H2O(l)

with enthalpy of reaction

ÎHrxnâ=65.2kJ/mol

What is the enthalpy of formation of CaO(s)?

Express your answer in kilojoules per mole to one decimal place.

________

7- Part A

Write a balanced chemical equation depicting the formation of one mole of H2O2(g) from its elements in their standard states.

Express your answer as a chemical equation. Identify all of the phases in your answer.

_____

Part B

For H2O2(g), find the value of ÎHâf. (Use Appendix C)

Express your answer using five significant figures.

_____

PART C: Write a balanced chemical equation depicting the formation of one mole of CaCO3(s) from its elements in their standard states.

Express your answer as a chemical equation. Identify all of the phases in your answer.

_____

Part D

For CaCO3(s), find the value of ÎHâf. (Use Appendix C)

Express your answer using five significant figures.

_____

Part E

Write a balanced chemical equation depicting the formation of one mole of POCl3(l) from its elements in their standard states.

Express your answer as a chemical equation. Identify all of the phases in your answer.

____

Part F

For POCl3(l), find the value of ÎHâf. (Use Appendix C)

Express your answer using four significant figures.

_____

Part G

Write a balanced chemical equation depicting the formation of one mole of C2H5OH(l) from its elements in their standard states.

Express your answer as a chemical equation. Identify all of the phases in your answer.

_____

Part H

For C2H5OH(l), find the value of ÎHâf. (Use Appendix C)

Express your answer using four significant figures.

Practice problems for exam 2 ______________

Useful Information:

h=6.626Ã10-34JÂ·s.; c=3.0Ã108 m/sec; E=hï® ; E= hc , ï¬ = h/mv; 1J = 1 kg-m2/s2 ï¬

mass of electron = 9.11 Ã 10-28 g, ïE= q + w ; 1 cal = 4.184 Joules Please Show all Work

1. Which of the following substances have standard heats of formation that are equal to zero by definition (circle your answers): H2(g), H(g), O3(g), H2O(s), H2O(l), Hg(l), Hg(s), Hg(g).

2. Limestone stalactites are formed in the reaction: Ca2+(aq) + HCO3-(aq) ï CaCO3(s) + CO2(g) +

H2O(l)
If one mole of CaCO3 is produced at 298 K under one atmosphere of pressure, the reaction performs 590 calories of expansion work, pushing back the atmosphere as CO2 is formed. At the same time, 9310 calories of heat are absorbed from the environment. What is ïE in Kcal/mole for CaCO3.

3. What is the minimum wavelength of light in AÌ (1 AÌ = 10-8 cm) needed to provide enough energy per quantum to rupture the chemical bond in hydrogen iodide (HI). The bond dissociation energy of HI is 71.4 Kcal/mole.

4. Sketch the shape and orientation of the following types of orbitals: s, px, dxy, dz2, dx2-y2

5. Give the values of (n) , (l) and (ml) for each orbital in the 4p subshell.

6. Write the complete electron configuration for the following: Ti 2+_____________________________________ Cr_______________________________________

N______________________________________

7. Calculate the standard enthalpy of formation ( ï Ho) for diamond from graphite [i.e. C (graphite) ï C (diamond)] given that:

C (graphite) + O2 ï CO2 (g) ( ï Ho = -393.5 KJ/mole) C (diamond)] + O2 ï CO2 (g) ( ï Ho = -395.4 KJ/mole)

If 1.0g of graphite is converted to diamond, what is the energy change? Is this an endothermic or exothermic reaction?

8. An 160 pound astronaut on his way to Mars is buzzing along at 10,000 miles per hour. (a) Express his weight in grams (one pound = 454 grams) so that you can calculate the astronautâs wavelength (1mile/hour = 44.7 cm/sec)

(b) Suppose the astronaut detects outside his spacecraft a proton (m=1.7 x 10-24 g) from a âsolar windâ moving at exactly the spacecraft velocity. What is the proton wavelength is in AÌ (1 AÌ = 10-8 cm.

9. What is the maximum number of electrons that can occupy each of the following subshells? a) 3d_________________ b) 1s____________________ c) 2p ____________________

10. Identify the element represented by the following electronic configuration.

a) [Ne] 3s2____________________

b) What is the electron configuration for the first excited state of this atom.______________

11. Determine the number of valence electrons for each element.
(a) Br___________ (b) Na _________ (c) Sn __________

12. 175 g of Fe at 15.0oC is mixed with 225 g of H2O at 95.0oC. What is the final temperature of the mixture? The specific heats of iron= 0.448 J/g oC and water = 4.184 J/g oC). (keep in mind the following: heat gained + heat lost = 0 and q=mass x heat capacity x ïT)

13. (5 pts) Calculate values of ÎHrxn for the following reactions: CS2(g) + 3O2(g) ï® CO2(g) + 2SO2(g)

The heat of formation for the following substances is given in kJ/mol:

CS2 CO2 SO2 117.4 -393.51 -296.83

14. (6 pts) Use the electron configuration of Li and Be and determine which element has the greatest second ionization energy. Defend your answer.

15. Mark beside each of the following processes either âexoâ or âendoâ according to whether you think the process will release heat or absorb heat.

a. Ca(g) ï Ca(g)+2 + 2e-
b. I(g)+1e-ï I(g)-1
c. Ca(g)+2 + S(g)-2 ï CaS(s) d. I2(g)ï 2I(g)

( ) ( ) ( ) ( )

16. (6 pts) In each of the following pairs, which of the two species is larger?
a) O-2 or Na+ b) Ti+4 or Ti+2 c) B or C d) N or N-3

17. Write down the Lewis dot structure for the following (a) N_______________ (b) Ne________________

18. THE BORN HABER CYCLE: I may have a problem on the Born Haber cycle. Please check my lecture notes to see how to set up the process and then calculate the lattice energy from the various thermodynamic quantities such as in the NaCl example below;

ï H ï¯ f NaCl = -411KJ

Na(s) ï® Na(g) ï H =108KJ
1â2 Cl2 ï® Cl(g) ï H = 122KJ Ionization Energy of Na ï H = 496 KJ Electron affinity of Cl ï H = -349KJ

CHEM 1B Lecture Notes - Lecture 2: Heat Capacity, Calorimetry, Jmol

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