Search found 31 matches

by Rachael_1H
Tue Mar 08, 2016 4:39 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: pH and cell potential
Replies: 5
Views: 5648

Re: pH and cell potential

Why would the pOH decreasing cause the OH- concentration to increase? Wouldnt it decrease according to the equation pOH=-log[OH-]?
by Rachael_1H
Thu Feb 25, 2016 9:40 pm
Forum: *Identifying Primary, Secondary, Tertiary, Quaternary Carbons, Hydrogens, Nitrogens
Topic: Tert vs neo
Replies: 2
Views: 419

Tert vs neo

Are the prefixes "neo" and "tert" interchangeable? If not, how do you know when to use which?
by Rachael_1H
Wed Feb 24, 2016 5:03 pm
Forum: *Cycloalkanes
Topic: naming compounds
Replies: 1
Views: 496

naming compounds

How do you know what to capitalize when naming compounds? For example, 4-tert-Butyl-1,2-dimethylcyclohexane has a capitol "B" in "Butyl" but not a capitola "M" for "methyl". Why? When do you and do you not capitalize?
by Rachael_1H
Thu Feb 04, 2016 11:14 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Significant Figures
Replies: 1
Views: 313

Significant Figures

When Calculating K with the equation log K=(n)(standard E)/(0.0592), using the values log K=(2)(-.45 V)/(0.0592), K=6.27*10^-16 but the book rounds this value to K=6*10^-16. Why is only one significant figure the correct amount of sig figs? Shouldn't it be 2 sig figs because the mantissa of the loga...
by Rachael_1H
Thu Feb 04, 2016 10:31 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Standard potential and K
Replies: 2
Views: 568

Standard potential and K

If the standard potential of cathode > standard potential of anode, why does the reaction favor products? And what does this have to do with K>1? From looking at a list of reactions, how would you know which have a value of K>1?
by Rachael_1H
Thu Feb 04, 2016 10:07 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Find stndrd potential of 0.5 rcn using stndrd delta G values
Replies: 1
Views: 290

Find stndrd potential of 0.5 rcn using stndrd delta G values

When calculating the standard potential for a half reaction, such as U4+ + 4e- ---> U, why do you have to convert the standard potentials of the half reactions U4+ + e- ---> U3+ and U3+ + 3e- ---> U to their standard delta G values, and then add their standard delta G values to find the standard pot...
by Rachael_1H
Thu Feb 04, 2016 9:59 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Writing cell diagram: figuring out order
Replies: 2
Views: 513

Writing cell diagram: figuring out order

When Writing a Cell Diagram, how do we know which order to put the different molecules of the anodes and cathodes in? For instance with the anode: Ag --->Ag+ + e- and the cathode: O3 + H2O + 2e- ---> O2 + 2OH- , the cell diagram is: Ag(s)|Ag+(aq)||OH-(aq)|O3(g),O2(g)|Pt(s) My question is: why is Ag ...
by Rachael_1H
Thu Feb 04, 2016 9:59 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Writing cell diagram: figuring out order
Replies: 2
Views: 340

Writing cell diagram: figuring out order

When Writing a Cell Diagram, how do we know which order to put the different molecules of the anodes and cathodes in? For instance with the anode: Ag --->Ag+ + e- and the cathode: O3 + H2O + 2e- ---> O2 + 2OH- , the cell diagram is: Ag(s)|Ag+(aq)||OH-(aq)|O3(g),O2(g)|Pt(s) My question is: why is Ag ...
by Rachael_1H
Mon Jan 25, 2016 12:08 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: calculating standard gibbs free energy of reation
Replies: 1
Views: 775

calculating standard gibbs free energy of reation

Calculate standard gibbs free energy of a reaction for the reaction showing the decomposition of mercury (II) oxide at 298 K. 2HgO(s)---> 2Hg(l) + O2(g) Standard reaction enthalpy of formation for HgO = -90.83 standard molar entropy HgO=70.29, Hg=76.02, and O2=205.14 When finding the standard gibbs ...
by Rachael_1H
Sun Jan 24, 2016 12:01 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard RXN Entropy/Enthalpy
Replies: 3
Views: 482

Re: Standard RXN Entropy/Enthalpy

Thank you. How do you know whether The reactants' bonds are breaking or forming? I understand that you look at the chemical equation, but for the equation
Ch4 + 2O2 ----> CO2 + 2H2O
For instance, are the reactants' bonds breaking? Does this make it exothermic?
by Rachael_1H
Sat Jan 23, 2016 11:51 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Knowing when a value is equal to zero
Replies: 2
Views: 377

Knowing when a value is equal to zero

A sample of one mole of gas initially at one ATM and 298 K is heated at constant pressure to 350 K then the gas is compressed isothermally to its initial volume and finally it is cooled to 298 K at constant volume. Which of the following values is zero? Delta S surroundings and Delta G Delta S syste...
by Rachael_1H
Thu Jan 21, 2016 7:41 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard RXN Entropy/Enthalpy
Replies: 3
Views: 482

Standard RXN Entropy/Enthalpy

When calculating the standard rxn entropy and enthalpy, using standard molar entropies and enthalpies, how do you know whether to subtract sum of products from sum of reactants, or vice verse? Our course reader says: Standard RXN Entropy/Enthalpy=(sum of products' standard molar entropies/enthalpies...
by Rachael_1H
Thu Jan 21, 2016 7:19 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Ideal Monatomic Gas Entropy
Replies: 1
Views: 492

Ideal Monatomic Gas Entropy

Why does "1 mol of the atoms of an ideal monatomic gas" have a greater change in entropy than "1 mol of atoms bound together as diatomic molecules" when temperature in increased? The book's answer key says it is because the 1 mol of atoms of an ideal monatomic gas has "a gre...
by Rachael_1H
Sun Jan 17, 2016 5:54 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Finding change in internal energy using PV=nRT equation
Replies: 3
Views: 1537

Finding change in internal energy using PV=nRT equation

Hi, I'm looking for help with homework question 8.49, which states, "Oxygen difluoride is a colorless, very poisonous gas that reacts rapidly with water vapor to produce O2, HF, and heat. It gives the formula OF2 (g) +H20 (g) --> O2 (g) + 2HF (g) with delta H being -318 kJ. What is the change i...
by Rachael_1H
Wed Jan 13, 2016 1:11 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacities
Replies: 1
Views: 318

Heat Capacities

20 grams of Copper at 100 degrees celsius is put in a vessel containing 50.7 grams water at 22 degrees celsius. Assume no energy is lost to surroundings. When finding the final water temperature, why do you set the +(heat released)= -(heat absorbed)? Why do you make the "heat absorbed" neg...
by Rachael_1H
Wed Jan 13, 2016 11:21 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Mean Bond Enthalpy
Replies: 2
Views: 667

Mean Bond Enthalpy

Using bond enthalpy to determine the enthalpy change of the rxn: H2(g) + (.5)O2(g) -----> H2O(l) The equation used is sum of bonds broken minus sum of bonds formed. Using the book's given bond enthalpies of diatomic molecules and mean bond enthapies, the answer key has the equation used as (H2 bond ...
by Rachael_1H
Thu Dec 03, 2015 11:01 am
Forum: *Titrations & Titration Calculations
Topic: HW 13.23
Replies: 3
Views: 498

Re: HW 13.23

How do you know the volume of acid added? Only the molarity of HCl, the acid, is given.
by Rachael_1H
Tue Nov 24, 2015 4:33 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Determine ranking of pH of solutions
Replies: 1
Views: 598

Determine ranking of pH of solutions

My question is from the text: 12.67) Rank the following solutions in order of increasing pH: A) .00005 M HCl B) .2 M CH3NH3Cl C) .2 M CH3COOH D) .2 M C6H5NH2 justify your ranking. How would you determine the ranking? Would you need to calculate the pH of each solution, and if so how would you do tha...
by Rachael_1H
Tue Nov 24, 2015 4:09 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Salt pH in Aqueous Solution
Replies: 1
Views: 334

Salt pH in Aqueous Solution

Can someone please explain this problem from the textbook to me, step by step? 12.65) Determine whether an aqueous solution of each of the following salts is basic, acidic, or neutral. Write a chemical equation to justify your answer. A. KBr B. AlCl3 C. Cu(NO3)2 I mainly am confused by why the answe...
by Rachael_1H
Tue Nov 24, 2015 11:12 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Electron withdrawing
Replies: 1
Views: 404

Electron withdrawing

What is electron withdrawing and how do we know how electron withdrawing a bond is?

For instance, the answer key to our text states that the bond between the CCl3 group and COOH group in C2HCl3O2 is more electron withdrawing than the CH3 group in C2H4O2, which makes C2HCl3O2 a stronger acid.
by Rachael_1H
Tue Nov 24, 2015 10:26 am
Forum: Conjugate Acids & Bases
Topic: Amphoteric
Replies: 1
Views: 342

Amphoteric

Hello,

"state whether the following oxides are acidic, basic, or amphoteric:
As2O3 and Bi2O3."

The answer key states that they are both amphoteric. How would we know this?
Please explain. Thanks.
by Rachael_1H
Thu Nov 19, 2015 11:13 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Writing Molarity of IONS as Logarithms: Solving Logarithms
Replies: 2
Views: 583

Writing Molarity of IONS as Logarithms: Solving Logarithms

In the Chemistry 14a Course Reader on page 139, Lavelle has written: " -log(1.7 * 10^(-12)) = -(-11.8) = 12 " I am confused how he got to the value -11.8 from the equation -log(1.7 * 10^(-12)). Could someone please explain to me how to solve this logarithm (along with logarithms in general...
by Rachael_1H
Sun Nov 08, 2015 10:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reaction Quotient Q
Replies: 1
Views: 389

Reaction Quotient Q

Problem 11.13 from our book states "Write the reaction quotient Q for: 2BCl 3 + 2Hg => B 2 Cl 4 + Hg 2 Cl 2 " and in our answer key the answer is \frac{1}{P_{BCl_{3}}} I am confused at how to get to this answer. I thought that we find Q the same way that we find K: [products]/[reactants] H...
by Rachael_1H
Wed Oct 28, 2015 1:26 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles for Angular, T-shaped, etc.
Replies: 4
Views: 674

Re: Bond Angles for Angular, T-shaped, etc.

Yes the bond angles would be slightly less than 90 degrees because of the two lone paires
by Rachael_1H
Sat Oct 24, 2015 10:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles for Angular, T-shaped, etc.
Replies: 4
Views: 674

Bond Angles for Angular, T-shaped, etc.

Hello,

How do we determine the bond angles for angular, trigonal pyramidal, t-shaped, see-saw, and square pyramidal molecules? They are not written in the book on page 109.
by Rachael_1H
Sun Oct 11, 2015 11:02 pm
Forum: Empirical & Molecular Formulas
Topic: Quiz 1 Preparation: Naming Simple Compounds
Replies: 1
Views: 405

Quiz 1 Preparation: Naming Simple Compounds

"How many grams of ammonium chloride are needed to have 3.4 * 10^(-4) moles?" From this question, which is from the second Quiz #1 Self Preparation Quiz, how are we supposed to figure out the formula for ammonium chloride without outside resources? Are there certain formulas that we are su...
by Rachael_1H
Sun Oct 11, 2015 10:57 pm
Forum: SI Units, Unit Conversions
Topic: Units on Quiz #1 Preparation [ENDORSED]
Replies: 1
Views: 424

Units on Quiz #1 Preparation [ENDORSED]

"Calculate the volume of .642 M KOH that should be used to make 1.00 L of .101 M KOH." Why is the answer to this in mL when the unit of L is used within the problem? The correct answer to the problem is 157 mL according to the answer key, but would answering the question with .157 L be con...
by Rachael_1H
Tue Oct 06, 2015 3:09 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Multi electron atom effective nuclear charge
Replies: 1
Views: 335

Multi electron atom effective nuclear charge

In our text it states that "an effective nuclear charge for an electron in a p-orbital is lower than an electron in an s-orbital in the same shell" for multi electron atoms. I am confused because our course reader states "s-electrons have a lower energy than p-electrons in the same sh...
by Rachael_1H
Tue Oct 06, 2015 3:03 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals: lobes vs. radial nodes
Replies: 1
Views: 725

Orbitals: lobes vs. radial nodes

Is a lobe the same thing as a radial node?
by Rachael_1H
Tue Oct 06, 2015 2:59 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals: lobes vs. radial nodes
Replies: 2
Views: 3204

Orbitals: lobes vs. radial nodes

Is a lobe the same thing as a radial node?
by Rachael_1H
Thu Oct 01, 2015 9:44 pm
Forum: Empirical & Molecular Formulas
Topic: Sulfides
Replies: 1
Views: 330

Sulfides

Hello. What is a sulfide and how do we find a sulfide's molar mass? I came across a problem in the fundamentals section of the textbook that required knowledge of sulfides: "The molar mass of the metal hydroxide M(OH)2 is 74.10 g/mol. What is the molar mass of the sulfide of this metal?"

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