## Search found 17 matches

Sun Mar 19, 2017 7:54 pm
Forum: Phase Changes & Related Calculations
Topic: General formula for phase changes for enthalpy.
Replies: 2
Views: 519

### Re: General formula for phase changes for enthalpy.

For something with multiple phase changes and temperature changes, we use both the q=m*C*delta_T formula and the q=n*delta_H formulas. For example: If we we have a change in temperature of water from -5 degrees centigrade to 125 degrees centigrade, then we will need to use the q=m*C*delta_T for the ...
Sun Mar 19, 2017 6:54 pm
Forum: Second Order Reactions
Topic: Pre- equilibrium approach [ENDORSED]
Replies: 3
Views: 590

### Pre- equilibrium approach[ENDORSED]

When are we supposed to use the pre equilibrium approach? If there is an intermediate in the first step and the first step is also the slow step, would we need to use the pre-equilibrium approach to find the rate law and get rid of the intermediate?
Sun Mar 19, 2017 6:51 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalyst
Replies: 16
Views: 1519

### Re: Catalyst

In a two step reaction, if there is a initial reactant that shows up as a final product, is it a catalyst? Meaning the reactant was unchanged and unaffected?
Sun Mar 19, 2017 6:45 pm
Forum: *Alkanes
Topic: Naming [ENDORSED]
Replies: 92
Views: 10358

### Re: Naming[ENDORSED]

You would use dashes to separate the position of the substituents or functional group from the type of substituent or functional group. Also, we use them to separate the position of a double bond or triple bond. For Example: 3,2-dimethylbutane 2-ethylpent-1-ene --------> 1 represents the carbon that...
Thu Mar 02, 2017 9:18 am
Forum: *Organic Reaction Mechanisms in General
Topic: Solution is "decolorized" (Quiz 3 Prep)
Replies: 1
Views: 288

### Solution is "decolorized" (Quiz 3 Prep)

When ethene is bubbled through bromine water, the solution is decolorized. Which of the following is true regarding the reaction? 1. Br2 acts as a nucleophile 2. Br2 attacks the carbons of the double bond in one step. 3. The first step is the removal of a hydrogen atom to form [C2H3]- 4. The Br- ion...
Thu Mar 02, 2017 9:04 am
Forum: Administrative Questions and Class Announcements
Replies: 6
Views: 850

When will the quiz 3 preparation answers be posted?
Sun Feb 26, 2017 4:43 pm
Forum: *Nucleophiles
Topic: Naming type of reactant and commenting on reaction.
Replies: 1
Views: 243

### Naming type of reactant and commenting on reaction.

What type of reactant is cyanide? Draw its Lewis structure and comment on how it can react. What is the hybridization of the carbon and nitrogen atoms?
I found this question in the OChem textbook. Please explain how to solve this.
Mon Feb 20, 2017 11:53 am
Forum: Administrative Questions and Class Announcements
Topic: Quiz 2 Winter 2017
Replies: 160
Views: 17533

### Re: Quiz 2 Winter 2017. Help on Quiz 2 Prep please!

It is important to distinguish between the reaction and the rate constant. The units of rate constant are always M * s^-1. True or False.

Wed Feb 08, 2017 6:15 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Calculating Equilibrium constant
Replies: 1
Views: 215

### Calculating Equilibrium constant

The standard reaction free energy for H2(g)+I2(g) <-->2HI(g) is DeltaG = -21.1 kj at 500K. In a sealed reaction container, the equilibrium partial pressures of the gases are PH2= 1.2 bar, PI2 = 1.5 bar, and PHI is unknown. a) Calculate the value of the equilibrium constant for this reaction. b) Calc...
Mon Jan 30, 2017 3:50 pm
Forum: Administrative Questions and Class Announcements
Replies: 130
Views: 17514

### Re: Quiz 1 Preparation Answers

Can someone verify that the equation needed to solve #12 is the one we learned for calculating standard free energy change? I am getting caught up in the wording: "Calculate the standard Gibbs free energy". Should I be using a different equation (even though we're given standard change in...
Mon Jan 30, 2017 3:20 pm
Forum: Administrative Questions and Class Announcements
Replies: 130
Views: 17514

### Re: Quiz 1 Preparation Answers

Can someone please explain how I should approach #11? You divide 49.7 by the molar mass of PbO to get the number of moles, then multiply that by the deltaH to get the heat released by the reaction of that amount of PbO. You then use q=mCdeltaT and solve for m. 49.7g/(223.2g/mol)=0.223mol; 0.223mol*...
Mon Jan 30, 2017 2:15 pm
Forum: Administrative Questions and Class Announcements
Replies: 130
Views: 17514

### Re: Quiz 1 Preparation Answers

I am also wondering about #9, specifically about ΔS(surr), why is it not 0? Isn't it a state function, too? Please read carefully: Changes in state functions of the system are zero when the system returns to the same initial conditions. Delta S (total) > 0 for this process. Therefore delta S (surro...
Sun Jan 29, 2017 9:10 pm
Forum: Administrative Questions and Class Announcements
Replies: 130
Views: 17514

### Re: Quiz 1 Preparation Answers

What equation do we use for work in #3?
Sun Jan 22, 2017 8:08 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Chapter 8 Question 65
Replies: 2
Views: 382

### Re: Chapter 8 Question 65

Hi, After getting the enthalpy of the reaction to be -169.2 kJ, it should be easier to understand if you write out the whole process. The enthalpy of the reaction should equal the enthalpy of the products minus the reactants of the equation 2NO + 3/2O2 --> N2O5. Thus, you get -169.2 kJ = deltaHfN2O...
Sun Jan 22, 2017 7:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Chapter 8 Question 65
Replies: 2
Views: 382

### Chapter 8 Question 65

Can someone explain why -169.2 kJ (the enthalpy of the reaction 2NO + 3/2 O2 ---> N2O5) equals the enthalpy of formation of N2O5 minus twice the enthalpy of formation of NO?
Thu Jan 19, 2017 8:11 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Chapter 8 #59 [ENDORSED]
Replies: 3
Views: 509

### Re: Chapter 8 #59[ENDORSED]

What is the equation that is being used to solve for the reaction enthalpy in this problem?
Wed Jan 11, 2017 9:10 pm
Forum: Calculating Work of Expansion
Topic: Calculating the work done when water freezes and expands
Replies: 1
Views: 2895

### Calculating the work done when water freezes and expands

How do we calculate for the answer of Self-Test 8.1A in the the Chemical Principles 6e textbook? It is the example about finding the work that water does when it freezes and pushes back the metal wall of a pipe...