CAS CH 171 Lecture 5: CH171 Unit 3 Notes

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30 Apr 2018

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Classifying Reactions

• Chemical Reactions

• Non Redox Reaction

• Combination

• Double Replacement

• Decomposition

• Redox

• Combination

• Single Replacement (substitution)

• Decomposition

• *Redox = Reduction-Oxidization

• Reduction - gain of electrons

• can also mean: to combine with oxygen/to lose hydrogen/to decrease in oxidization number

• Oxidization - loss of electrons

• can also mean: to combine with oxygen/to lose hydrogen/to increase in oxidization number

• Will usually match the charge on the element’s ion

• Oxidization Number Rules

• 1. Any uncombined element is zero (homoatomic - ex: O2)

• 2. The oxidation number of monatomic ion is simply its charge (ex: Na+ = oxidization number

of 1+)

• 3. The oxidization number of group 1A = 1+, 2A = 2+, 3A = 3+, etc (ex: Ca = 2+)

• 4. Hydrogen will always be 1+

• 5. Oxygen will always be 2- EXCEPT in peroxides (1-) where O2 is 0

• 6. The sum of the oxidization umbers in a compound = the overall charge

• 0 if the compound is neutral

• Reduction goes together with Oxidization

• If something is reduced, it is also oxidized

• If something is oxidized, it is also reduced

EXAMPLES:

1. ex: Na2SO4

=2Na+ + SO42-

(+1) + S + (-2 x 4) = -2

S = +6

2. ex: CO3-2

C + (-2 x 3) = -2

C = 4

3. ex: NO2

N + (-2 x 2) = 0

N = +4

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4. ex: list the oxidation numbers…

4NO2 (g) + O2 —> 2N2O5 (g)

4NO2 : N = +4, O = -2

O2 : O = 0

2N2O5 : N = +5, O = -2

N: goes from +4 to +5 —> so N is OXIDIZED

O: goes from 0 to -2 —> so O is REDUCED

*NO2 = the reducing agent (responsible for reducing O2) while O2 is the oxidizing agent (responsible for

oxidizing NO2)

6. ex: list the oxidation numbers and determine which is the reducing agent and which is the oxidizing

agent

CH4 (g) + 2O2 (g) —> CO2 (g) + 2H2O (g)

CH4 : C + (+1 x 4) —> C = -4, H = +4

2O2 :O = 0

CO2 : C + (-2 x 2) —> C = +4, O = -2

2H2O : H + (-2 x 1) —> H = +2, O = -2

C: goes from -4 to +4 —> so C is OXIDIZED

O: goes from 0 to -2 —> so O is REDUCED

H: goes from +4 to +2 —> so H is REDUCED

CH4 = reducing agent

O2 = oxidizing agent

Combination Reaction - when there are multiple components that combine to form one product

• format: A + B —> C

• Can be redox OR non-redox

• Redox: 4NO2 (g) + O2 (g) —> 2 N2O5

• Non-redox: SO3 (g) + H2O (l) —> H2SO4 (aq)

Decomposition: when one reactant forms multiple components

• format: A —> B + C

• Can be redox OR non-redox

• Redox: 2H2O —> 2H2 (l) + O2 (g)

• Non-redox: CaCO3 (s) —> CaO (s) + O2 (g)

Single Replacement:

• format: A + Bx —> B + Ax

• Must always be redox

Double Replacement

• format: Ax + By —> Ay + Bx

• must always be non-redox

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EXAMPLE:

1. ex: classify the following reaction as redox or non-redox

CO2 (g) + H2O (l) —> H2CO3 (aq)

CO2 : (+4)(-2)

H2O : (+1)(-2)

H2CO3 : (+1) CO3-2

*non-redox reaction

2. ex: NaOH (aq) + HCl (aq) —> NaCl (aq) + H2O (l)

Molecular Equation: NaOH (aq) + HCl (aq) —> NaCl (aq) + H2O (l)

Total Ionic Equation: Na+ (aq) + OH (aq) + H+ (aq) + Cl- (aq) —> Na+ (aq) + Cl- (aq) + H2O (l)

Spectator Ions = Na+, Cl- (seen on both sides)

Net Ionic Equation: OH (aq) + H+ (aq) —> H2O (l)

• Enthalpy = net H change

• H (product) - H (reactants) = Net H change

• thermal energy released = Exothermic (-)

• Converts chemical energy —> into thermal energy

• Effect: makes its surroundings warmer

• Location of heat (in equation): right side (reactants —> products + heat)

• Sign on net H change: negative

• thermal energy absorbed = Endothermic (+)

• Converts thermal energy —> into chemical energy

• Effect: makes it surroundings cooler

• Location of heat (in equation): left side (reactants + heat —> products)

• Sign on net H change: positive

• *net H changed = (-)2801 KJ/mol

• *1 calorie = 4.184 J

• *1 calorie (food) = 1kcal

ex: which has the strongest intermolecular forces?

• Cl2 (gas at room temperature)

• Br2 (liquid at room temperature)

• I2 (solid at room temperature)

*SOLIDS are strongest, LIQUIDS are weakest

*Dispersion Force - INCREASES as you move down a period

Physical properties of Solids, Liquids & Gases

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Document Summary

Any uncombined element is zero (homoatomic - ex: o2: 2. The oxidation number of monatomic ion is simply its charge (ex: na+ = oxidization number of 1+: 3. The oxidization number of group 1a = 1+, 2a = 2+, 3a = 3+, etc (ex: ca = 2+: 4. Oxygen will always be 2- except in peroxides (1-) where o2 is 0: 6. 2- (+1) + s + (-2 x 4) = -2. 4no2 : n = +4, o = -2. 2n2o5 : n = +5, o = -2. N: goes from +4 to +5 > so n is oxidized. *no2 = the reducing agent (responsible for reducing o2) while o2 is the oxidizing agent (responsible for oxidizing no2: ex: list the oxidation numbers and determine which is the reducing agent and which is the oxidizing agent. Ch4 (g) + 2o2 (g) > co2 (g) + 2h2o (g)

Related Questions

Initial observations: before beginning Observations Observations after 30 minutes Chemical equation Element that is oxidized Element that is reduced Spectator ion Oxidizing agent Reducing agent www.HOLscience.com 16 Â©Hands-On Labs, Inc. Experiment Oxidation-Reduction Activity Series Questions A. Define oxidation, reduction, and oxidation number. Describe how oxidation and reduction affect the oxidation number of an element. B. Define oxidizing agent, reducing agent, and spectator ion. C. In the reaction of copper and silver nitrate, a new substance appeared in the test tube. Describe the physical appearance of the substance and identify its chemical formula. D. Given an activity series in which the most active metals are at the top of the list and the least active metals are at the bottom of the list, would copper be listed above silver or would silver be listed above copper? Support your answer with data from Data Table 1. E. Solid copper sulfide and silver nitrate react to form copper (II) nitrate and solid silver sulfide. Write a balanced chemical equation that describes the reaction. Identify the oxidation number of each element in the reaction. (You do not need to include the total contribution of charge.) Is this reaction a redox reaction or a non-redox reaction? Explain your answer. www.HOLscience.com 17 Â©Hands-On Labs, Inc. Experiment Oxidation-Reduction Activity Series Exercise 2: Creating an Activity Series Data Table 2. Redox Reactions of Copper, Lead, and Zinc Solid metal Well ID Solution Immediate observations 30 Minute Observations Cu A1 Pb(NO3 ) 2 A2 Zn(NO3 ) 2 Pb B1 CuSO4 B2 Zn(NO3 ) 2 Zn C1 CuSO4 C2 Pb(NO3 ) 2 Data Table 3. Potential Redox Reactions and Chemical Equations Metal and Metallic Solution Reaction Occurred? Chemical Equation Cu + Pb(NO3 ) 2 Cu + Zn(NO3 ) 2 Pb + CuSO4 Pb + Zn(NO3 ) 2 Zn + CuSO4 www.HOLscience.com 18 Â©Hands-On Labs, Inc. Experiment Oxidation-Reduction Activity Series Zn + Pb(NO3 ) 2 Questions A. List each of the metals tested in Exercise 2. Indicate the oxidation number when each element is pure and the oxidation number when each element is in a compound. B. Which of the metals in Exercise 2 was the strongest oxidizing agent? Was there an instance when this metal also acted as a reducing agent? Explain your answer using data from Data Table 3. C. Which of the metals in Exercise 2 was the strongest reducing agent? Was there an instance when this metal also acted as an oxidizing agent? Explain your answer using data from Data Table 3. D. How does ease of oxidation correlate with activity? Do highly active metals tend to donate electrons or accept electrons from other metals? E. Create an activity series for copper, lead, and zinc. Place the most active metal at the top of the list.

1. (1 point) What are transferred in an oxidation-reduction reaction? *

â¢ atoms

â¢ electrons

â¢ ions

â¢ protons

2. (1 point) In the reaction of beryllium with fluorine, which atom is oxidized? *

â¢ fluorine

â¢ beryllium

â¢ neither of them

â¢ both of them

3. (1 point) Ag - - > Ag ^+ +1 e^- This equation represents the type of reaction called _____. *

â¢ hydrolysis

â¢ oxidation

â¢ redox

â¢ reduction

4. (1 point) What is the reducing agent in the following reaction? 2K + S - - > K2S *

â¢ K

â¢ S

â¢ K2S

â¢ None of the above

5. (1 point) The oxidation number of oxygen when it is in a compound other than a peroxide is ____. *

â¢ -2

â¢ -1

â¢ 0

â¢ +2

6. (1 point) What is the oxidation number for each atom in NH4F? *

â¢ N=+3, H=-4, F=+1

â¢ N=-3, H=+1, F=-1

â¢ N=+3, H+1, F=-1

â¢ N=-3, H=-1, F=+1

7. (1 point) Which atom has a change in oxidation number of +4 in the following redox reaction?K2Cr2O7 + H2O + S - - > KOH + Cr2O3 + SO2 *

â¢ K

â¢ Cr

â¢ O

â¢ S

Metal activity series for question 8

8. (1 point) Of the following metals, which ions are most easily reduced? Use the above table to answer the question. *

â¢ magnesium

â¢ lead

â¢ copper

â¢ sodium

9. (1 point) In a zinc-copper cell, Zn(s) | Zn^+2(1M) || Cu^+2(1M) | Cu(s), which electrode is positive? *

â¢ Cu^+2

â¢ Cu(s)

â¢ Zn(s)

â¢ Zn^+2

10. (1 point) How must a redox reaction that is to be used as a source of electrical energy be set up? *

â¢ One half reaction must involve two metals.

â¢ Two half reactions must use a metal wire electrodes.

â¢ One half reactions must involve more than one electron.

â¢ Two half reactions must be physically separated.

11. (1 point) In a voltaic cell at which electrode does reduction occur? *

â¢ anode only

â¢ cathode only

â¢ both anode and cathode

â¢ Either anode or cathode , depending on the metal

12. (1 point) What assures that there is no charge build up in a voltaic cell as oxidation and reduction occur? *

â¢ one of the half cells

â¢ the electrolyte solutions

â¢ the moving electrons

â¢ the salt bridge

13. (1 point) In the most common dry cell what material is the electrode that is the center rod made of? *

â¢ copper

â¢ graphite

â¢ lead

â¢ zinc

14. (1 point) To charge a lead storage battery you must ________. *

â¢ apply a direct current to it.

â¢ hold a magnet close to it.

â¢ Use alternating current through it.

â¢ increase the oxygen in it.

15. (1 point) In a hydrogen- oxygen fuel cell ______________. *

â¢ hydrogen diffuses through the cathode.

â¢ hydrogen and oxygen are mixed before entering the anode.

â¢ oxygen diffuses through the anode.

â¢ oxygen diffuses through the cathode.

16. (1 point) When electrical energy is used to cause a chemical reaction we call this process _____. *

â¢ electronation

â¢ electrolysis

â¢ hydration

â¢ reduction

17. (1 point) Which of the following is true about an electrolytic cell? *

â¢ It changes chemical energy into electrical energy.

â¢ It is the type of cell used in electrocution

â¢ It uses an electric current to make a nonspontaneous reaction go.

â¢ All of the above

18. (1 point) The products formed in the net reaction of the electrolysis of water are ____. *

â¢ aqueous hydrogen ion and hydroxyl ion

â¢ hydrogen gas and oxygen gas

â¢ hydrogen gas and liquid oxygen

â¢ water vapor

19. (1 point) What occurs in electroplating? *

â¢ decomposition of an ionic compound

â¢ decomposition of a salt layer

â¢ deposition of a metal layer on a material

â¢ deposition of a salt layer on a metal

Open response Questions : Answer questions 20 through 22 in complete sentences

20. ( 5 points) Write the equation for the reaction of calcium and oxygen ( 1 point). Write the oxidation numbers for both the reactants and the products ( 2 points) What is the reducing agent and why? ( 2 points)

21. ( 5 points) Tell how a voltaic cell works. Be sure to mention the various parts of the voltaic cell and what they have to do with how it works.

22. (4 points) What are the signs given to the electrodes in both the voltaic and electrolytic cells? What reaction (oxidation or reduction) is occurring at each?

peargnat685

HERE IS HOW THIS IS GOING TO WORK! IF YOU ANSWER THE QUESTIONS IWILL GIVE YOU THE 3K POINTS + MORE AFTER I REPOST IT.

2. The amount of heat involved in the synthesis of 1 mole of acompound from its elements, with all substances in their standardstates at 25*C, is called _________.

3. What is a valid unit for specific heat?

4. Use Hess's Law to find the heat of reaction in the examplebelow.

N2O4 (g) ----> 2NO2 (g)

Given that:

N2O4 (g) ----> N2 (g) + 2O2 (g) (Delta H =-9.7kJ)

2NO2 (g) ----> 2O2(g) + N2(g) ( Delta H= -67.7kJ)

5. Use Hess's Law to find the heat of reaction in the examplebelow. (Example doesn't exist btw.)

6. (Delta H) for the formation of rust (Fe2O3) is -826 kJ/mol. Howmuch energy is involved in the formation of 5 grams ofrust?

7. How many kilocalories of heat are required to raise thetemperature of 50g of aluminum from -5*C to 35*C? (Specific heat ofAluminum = 0.21 cal/g*C)

8.Calculate the (Delta H) for this reaction:

Zn(s) + Cu (2+ ion)(aq) ---> Zn(2+) + Cu(s)

(Delta H) for Cu(2+) = +64.4 kJ/Mol; (Delta H) for Zn(2+) = -152.4kJ/mol

9. The following equation shows the reaction that occurs whennitroglycerine explodes.

4C3H5O9N3 ----> 12CO2 + 6N2 + O2 +10H2O + 1725 Kcal

Is this reaction exothermic , endothermic, a combustion reaction ,or a combination reaction?

10. What does it mean for ammonia, (NH3) to have a (Delta H f) =-46 kJ/mol?

(for example: Define heat of formation. What does a negative heatof formation mean? what do the units of kJ/mol mean?)

11. What is the maximum amount of KCl that can dissolve in 500g ofwater?

(solubility of KCl is 34 g/ 100g of water at 20*C)

12.List the ways(operations) that can help make a substancedissolve faster in a solvent?

13. If a crystal added to an aqueous solution causes many particlesto come out of solution, the original solution was (saturate,unsaturated, supersaturated).

14. What is the number of moles of solute in 165 mL of a 0.82 Msolution?

15. What mass of NaCl is needed to make 350 mL of a 1.00 Msolution?

16. Colligative properties depend upon...

17. If one mole of each of these solutes in added to the sameamount of water, which solution has the highest boiling point?(glucose, aluminum sulfate, magnesium acetate, copper (I)chloride)

18. When an acid reacts with a base, what compounds areformed?

19. If the [H+] in a solution is 1x10^(-13) mol/L, what is the[OH-]?

20. If the [OH-] = 1x10^-6 mol/L, what is the pH of thesolution?

21. For a solution to be considered acidic what must be thehydrogen-ion concentration?

22. Which of the following represents a Bronsted-Lowry conjugateacid-base pair?

a) SO3(2-) and SO2 b) CO3(2-) and CO c) H3O and H2 d) NH4(+) and NH3

23. With solutions of "strong" acids and "strong" bases, the word"strong" refers to ...

24. What are the products of Al(OH)3 + H2CO3?

25.What is the concentration of hydrochloric acid if 5.0 mL of acidis neutralized by 30.0 mL of 2.00M sodium hydroxide.

26. At equilibrium, what is the rate of production of reactantscompared with the rate of production of products?

27. What is the equilibrium constant for the following reaction2SO3 ---> 2SO2 + O2

28. How does an increase in pressure affect the following reaction?2SO3 (g) --> 2SO2(g) +O2(g)

29.What stresses would shift the reaction to the right?

2SO3(g) ==> 2SO2(g) + O2(g)

30. The Keq of a reaction 4.9 x 10^(-7). Are products or reactantsfavored at equilibrium?

31. In which of these systems is the entropy decreasing?

a) air escaping from a tire b) snow melting c) a gas condensing d) salt dissolving inwater

32. If an atom is reduced in a redox reaction, what must occur toanother atom in the system?

33. Identify the oxidizing agent in the following reaction: 2Na + S---> Na2S

34. What are transferred in an oxidation -reductionreaction?

35. Give the oxidation number for each atom in KMnO4.

36. Which atom has a change in oxidation number of +4 in thefollowing reaction?

K2Cr2O7 + H2O + S ----> KOH + Cr2O3 +SO2

37. What is the oxidation number of sulfur in each of the following:

a. SO3 c.SO2(2-)

b. Na2SO4 d. S2O4 (2-)

38.Fe(3+) ----> Fe represents oxidation, reduction, orhydrolysis?

39. When the half reactions Br2+ 2e- -----> 2Br- and Na---->e- + Na(+) are combined the balanced redox equation is_____________________ ( WRITE the BALANCED REDOX eq)

40. To balance the oxygen and hydrogen for a redox reaction thattakes place in basic solution, it is necessary to use whichsubstance?

41. What particle completes this nuclear equation? 55/25 Mn + 2/1 H====> _____ +2 1/0 n

42. The half-life of tungsten-182 (182/74 W) is 1.1x10^(17) years.How long would it take for a 376.2 kg sample to decay until only123.0 grams remain?

43. After 3 days, the quantity of certain radioisotope is reducedfrom 13.6 grams to 1.9 grams. Calculate the half-life of theisotope.

44. What is the name of the compound having the formulaC8H18.

45. What is the name of the following compound:

CH3---CH2----CH---CH2--C

I \

CH3 OH

46. What is an isomer? Give an isomer of hexane (C6H14) and drawit's structure.

47. What is the name of the hydrocarbons with double covalentbonds?

48. Draw the stucture for 3-methylbutanoic acid.

49. Draw the structure for methylbenzene?

50. What is the name of the following compound:

CH3----C-----CH3

CH3

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CAS CH 171 Lecture 5: CH171 Unit 3 Notes

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