Search found 100 matches
- Sun Mar 15, 2020 6:37 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Midterm 6B
- Replies: 3
- Views: 425
Midterm 6B
Q6B. For which process will ∆Ho and ∆Go be expected to be most similar? Ans ____A (3pt) (A) 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s) (B) 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) (C) 2NO2(g) → N2O4(g) (D) 2H2(g) + O2(g) → 2H2O(g) Do you have to calculate both delta H0 and delta G0 to determine the answer to...
- Sun Mar 15, 2020 6:25 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Midterm 3D
- Replies: 1
- Views: 195
Midterm 3D
How do you solve midterm Q3D? Why is the net charge -1 and not 0?
At pH 6 what is the net charge for acetic acid, CH3COOH (pKa= 4.75)?
At pH 6 what is the net charge for acetic acid, CH3COOH (pKa= 4.75)?
- Sun Mar 15, 2020 6:21 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Midterm 3B
- Replies: 1
- Views: 246
Midterm 3B
How do you solve midterm question 3B? How do the concentrations affect delta T? Which combination of solutions of HCl and NaOH would produce the largest ∆T? (3pt) Ans _____B (A) 50 mL of 1 M HCl with 50 mL of 1 M NaOH (B) 50 mL of 2 M HCl with 50 mL of 2 M NaOH (C) 100 mL of 1 M HCl with 50 mL of 2 ...
- Sun Mar 15, 2020 6:19 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Molecularity
- Replies: 4
- Views: 323
Re: Molecularity
We need to be able to identify the molecularity of a reaction or its elementary steps.
- Sun Mar 15, 2020 6:15 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Test 2 Q6 part b ii
- Replies: 5
- Views: 380
Test 2 Q6 part b ii
In part b of number 6 on Test 2: A concentration cell was constructed with two electrodes containing CuSO4 at 25 degrees C. The cathode concentration is 2.2 M and cell potential is 0.0213 V. How will the following changes affect the cell potential? ii) halving the mass of the anode electrode Why doe...
- Sat Mar 14, 2020 7:17 pm
- Forum: Zero Order Reactions
- Topic: units of k
- Replies: 5
- Views: 470
Re: units of k
Depending on the order of each reactant, certain concentrations may be squared, which makes the unit M^2, affecting k.
- Sat Mar 14, 2020 7:14 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: elementary rate law
- Replies: 4
- Views: 339
Re: elementary rate law
The mechanism is made up of multiple elementary steps. Rate laws can be written for each of the elementary steps, and the overall rate law is determined by the slowest step.
- Sat Mar 14, 2020 7:00 pm
- Forum: Balancing Redox Reactions
- Topic: balancing h and o
- Replies: 7
- Views: 524
Re: balancing h and o
You can balance the O atoms first with H2O, then balance the H atoms using H+.
- Sat Mar 14, 2020 6:59 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Platinum
- Replies: 2
- Views: 159
Platinum
Why is platinum commonly used as an inert electrode compared to other metals?
- Sat Mar 14, 2020 4:01 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Order of Reactions
- Replies: 4
- Views: 406
Order of Reactions
How does the order of a particular reactant differ from the order of an entire elementary step rate law?
- Sat Mar 14, 2020 3:56 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: kinetics vs. thermodynamics
- Replies: 23
- Views: 1191
Re: kinetics vs. thermodynamics
Kinetics favors reactions with low activation energy, as the reaction will occur more quickly.
- Sat Mar 14, 2020 3:52 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Arrhenius Equation "A"
- Replies: 3
- Views: 304
Arrhenius Equation "A"
In a given reaction, does A stay constant or change depending on the other variables and conditions?
- Sat Mar 14, 2020 3:44 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Endgame Q15
- Replies: 2
- Views: 282
Endgame Q15
For question 15 part a:
For the reaction A + B → C, artificial lab conditions are created to make the concentration of A
exceptionally large compared to [B].
a) What is the point of this?
Is the purpose also to determine the order in reactant B?
For the reaction A + B → C, artificial lab conditions are created to make the concentration of A
exceptionally large compared to [B].
a) What is the point of this?
Is the purpose also to determine the order in reactant B?
- Sat Mar 14, 2020 1:31 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: UA Practice Final Q4
- Replies: 2
- Views: 294
UA Practice Final Q4
For question 4 on the UA practice final part a:
H2C2O4 ⇌ 2H+ + C2O42-, K = 3.78 x 10-6
a) What volume of 0.400 M NaOH is required to neutralize completely a 5.00 x 10-3 mol sample of pure oxalic acid?
How do you approach this problem? How do you determine the number of moles of H+?
H2C2O4 ⇌ 2H+ + C2O42-, K = 3.78 x 10-6
a) What volume of 0.400 M NaOH is required to neutralize completely a 5.00 x 10-3 mol sample of pure oxalic acid?
How do you approach this problem? How do you determine the number of moles of H+?
- Sat Mar 14, 2020 1:25 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: UA Practice Final Review Q10
- Replies: 1
- Views: 193
UA Practice Final Review Q10
On number 10 of the practice final review: Initially, a sample of ideal gas at 412 K occupies 12.62 L at 0.6789 atm. The gas is allowed to expand to 19.44 L by isothermal, reversible expansion. Calculate ΔStot, ΔS, and ΔSsurr for this pathway. Can you use PV/T instead of nR in the formula ∆S = nR ln...
- Sat Mar 14, 2020 8:25 am
- Forum: Student Social/Study Group
- Topic: Week 10 Review Question
- Replies: 5
- Views: 447
Re: Week 10 Review Question
We know that the equilibrium concentration of NH3 is 0.150 M, so using stoichiometric ratios and an ICE chart we can determine that the concentrations of N2 and H2 decrease by 0.075 M and 0.225 M, respectively.
- Sat Mar 14, 2020 8:14 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Review Problem for Week 10 #5
- Replies: 3
- Views: 261
Re: Review Problem for Week 10 #5
Similar to delta H of formation, delta G of formation is 0 for elements and diatomic gases like Cl2.
- Sat Mar 14, 2020 8:11 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Dr. Lavelle's week 10 review - last question
- Replies: 3
- Views: 324
Re: Dr. Lavelle's week 10 review - last question
Since you know the overall experimentally determined rate law, you can tell that the Student B mechanism matches because the second step is rate limiting (its elementary rate law matches the overall rate law).
- Sat Mar 14, 2020 8:08 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Week 10 Review Problems
- Replies: 4
- Views: 296
Re: Week 10 Review Problems
Yes, because Br2 is a gas, you must have Pt as the solid metal electrode on the right hand side.
- Fri Mar 13, 2020 12:01 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electrodes
- Replies: 4
- Views: 372
Electrodes
When writing cell diagrams, can you assume without being told in the question that Pt is the solid electrode? When can you assume this?
- Wed Mar 04, 2020 8:28 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6N.15
- Replies: 2
- Views: 123
6N.15
How do you solve problem 6N.15:
Calculate the potential of a cell constructed with two nickel electrodes. The electrolyte in one compartment is 1.0 M Ni (NO3)2. In the other compartment, NaOH has been added to a Ni(NO3)2 solution until the pH=11.0 at 298 K
Calculate the potential of a cell constructed with two nickel electrodes. The electrolyte in one compartment is 1.0 M Ni (NO3)2. In the other compartment, NaOH has been added to a Ni(NO3)2 solution until the pH=11.0 at 298 K
- Wed Mar 04, 2020 8:19 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6N.11
- Replies: 2
- Views: 501
6N.11
How do you solve problem 6N.11:
Use data from Appendix 2B to calculate the solubility product of Hg2Cl2 & compare this number with the value listed in Table 6I.1 and comment on any difference
Use data from Appendix 2B to calculate the solubility product of Hg2Cl2 & compare this number with the value listed in Table 6I.1 and comment on any difference
- Wed Mar 04, 2020 3:25 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6N.3 part c
- Replies: 2
- Views: 256
6N.3 part c
For question 6N.3 part c:
Pt (s)|Cl2 (g, 250 torr) | HCl (aq, 1.0 M) ||HCl (aq, 0.85 M) | H2 (g, 125 torr)|Pt (s)
How do you predict the cell potential using the Nernst equation? Do the partial pressures of the gases need to be converted into concentrations?
Pt (s)|Cl2 (g, 250 torr) | HCl (aq, 1.0 M) ||HCl (aq, 0.85 M) | H2 (g, 125 torr)|Pt (s)
How do you predict the cell potential using the Nernst equation? Do the partial pressures of the gases need to be converted into concentrations?
- Tue Mar 03, 2020 5:27 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic cells
- Replies: 3
- Views: 251
Galvanic cells
In a galvanic cell, is oxidation at the anode always on the left and reduction at the cathode always on the right? How do you determine which half reaction is the oxidation reaction and which reaction is the reduction reaction?
- Mon Mar 02, 2020 4:07 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6N.13
- Replies: 2
- Views: 185
6N.13
Which equation do you use to calculate Q for problem 6N.13?
- Mon Mar 02, 2020 3:59 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 6N.7 a
- Replies: 1
- Views: 195
6N.7 a
How do you solve problem 6N.7 a:
Calculate Ecell for each of the following concentration cells:
a) Cu (s)|Cu2+ (0.0010 mol/L)|| Cu2+ (0.010 mol/L)|Cu (s)
Calculate Ecell for each of the following concentration cells:
a) Cu (s)|Cu2+ (0.0010 mol/L)|| Cu2+ (0.010 mol/L)|Cu (s)
- Sat Feb 29, 2020 3:47 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt bridges
- Replies: 11
- Views: 735
Salt bridges
How does a salt bridge work and what is its effect on the battery?
- Wed Feb 26, 2020 3:17 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6L.7
- Replies: 3
- Views: 234
6L.7
How do you solve homework problem 6L.7? How do we know how to write the half-reactions?
- Tue Feb 11, 2020 2:41 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: 4H.1
- Replies: 1
- Views: 174
4H.1
In problem 4H.1: which substance in each of the following pairs has the higher molar entropy at 298K a) HBr or HF (gases) b)NH3 or Ne (gases) c) I2 (s) or I2 (l) d)1.0 mol Ar (g) at 1.00 atm vs at 2.00 atm, can anyone explain the difference in entropy for each part and why one is greater than the ot...
- Sat Feb 08, 2020 2:40 pm
- Forum: Calculating Work of Expansion
- Topic: 4A.7
- Replies: 3
- Views: 120
4A.7
How do you solve problem 4A.7: Calculate the heat that must be supplied to a copper kettle of mass 400 g containing 300 g of water to raise its temperature from 20 degrees to the boiling point, 100 degrees. What percentage of heat is used to raise the temperature of the water?
- Sat Feb 08, 2020 2:38 pm
- Forum: Calculating Work of Expansion
- Topic: 4A.3 part c
- Replies: 3
- Views: 127
4A.3 part c
How do you determine the change in internal energy in 4A.3 part c? Why does delta U not = w in this case?
- Wed Feb 05, 2020 9:41 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Heat capacity
- Replies: 4
- Views: 97
Heat capacity
How do you know the value of C at constant pressure and constant volume? What is C for an ideal gas?
- Tue Feb 04, 2020 4:28 pm
- Forum: Calculating Work of Expansion
- Topic: 4B.13 part a
- Replies: 1
- Views: 88
4B.13 part a
How do you solve part a of 4B.13, where the gas sample is expanding against a constant pressure of 1.00 atm?
- Mon Feb 03, 2020 10:17 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat capacity
- Replies: 3
- Views: 113
Heat capacity
Conceptually, what does heat capacity mean and how does constant volume heat capacity differ from constant pressure heat capacity?
- Sun Feb 02, 2020 4:26 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard States
- Replies: 2
- Views: 62
Standard States
What does it mean for reactants/products to be in their standard states?
- Sun Feb 02, 2020 3:59 pm
- Forum: Calculating Work of Expansion
- Topic: Reversible Processes
- Replies: 3
- Views: 111
Reversible Processes
In the expansion of a gas, how do you know if the process is reversible or not?
- Sat Feb 01, 2020 5:23 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Closed Systems
- Replies: 8
- Views: 387
Closed Systems
How do closed systems exchange energy with the environment but isolated systems do not?
- Sat Feb 01, 2020 5:21 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Pressure in an open beaker
- Replies: 12
- Views: 734
Pressure in an open beaker
In an open beaker system, how do we know that the system is at constant pressure?
- Wed Jan 22, 2020 3:59 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 6E.1
- Replies: 1
- Views: 118
6E.1
How do you calculate the pH of 0.15 M H2SO4?
- Wed Jan 22, 2020 3:54 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 6D. 15 part b
- Replies: 1
- Views: 103
6D. 15 part b
In problem 6D.15 part b, how do you find the pH of 0.055 M AlCl3?
- Sun Jan 19, 2020 9:56 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Weak acids & bases
- Replies: 7
- Views: 316
Weak acids & bases
How do you calculate the % protonated of a weak acid/base?
- Sun Jan 19, 2020 9:50 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Buffers
- Replies: 3
- Views: 115
Buffers
What is a buffer and how is it made?
- Sun Jan 19, 2020 9:49 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 7
- Views: 162
Re: Le Chatelier's Principle
Le Chatelier's principle predicts what will happen to a system if it is exposed to change- in pressure, volume, concentration of reactants/products, heat...
- Sun Jan 19, 2020 9:39 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: K less than 10^-3
- Replies: 5
- Views: 277
K less than 10^-3
What assumption do we make if K < 10^-3 and why does this make the change in the concentrations negligible?
- Sun Jan 19, 2020 9:36 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Pressure & Le Chatelier's Principle
- Replies: 6
- Views: 321
Pressure & Le Chatelier's Principle
How does changing the pressure of a system affect equilibrium?
- Sun Jan 12, 2020 1:02 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: when to use Kc vs Kp
- Replies: 11
- Views: 389
Re: when to use Kc vs Kp
The brackets indicate that the number inside is a concentration (molarity). Parentheses mean that the number is a partial pressure of a gas.
- Sun Jan 12, 2020 12:58 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Using the "ICE" box
- Replies: 8
- Views: 223
Re: Using the "ICE" box
Solids and liquids are also omitted from ICE box calculations because a negligible amount of the pure substances is used in the reaction. Solids and liquids don't have concentrations and are not included in the K expression or the ICE box.
- Sun Jan 12, 2020 12:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Concentration and partial pressure
- Replies: 2
- Views: 60
Concentration and partial pressure
How is the concentration of a gas related to its partial pressure, and when given an equilibrium expression should we assume we're given the concentration or partial pressure?
- Sun Jan 12, 2020 12:40 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5G.9
- Replies: 1
- Views: 53
5G.9
In problem 5G.9 part c, why is the ratio of partial pressure O2/partial pressure of O3 different for the two experiments?
- Sun Jan 12, 2020 12:31 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Le Chatelier's Principle
- Replies: 5
- Views: 181
Re: Le Chatelier's Principle
No, solids and liquids are present in a constant amount throughout the reaction so adding or removing some solid/liquid will not affect the reaction.
- Sat Dec 07, 2019 6:40 pm
- Forum: Conjugate Acids & Bases
- Topic: 6C.17
- Replies: 2
- Views: 210
6C.17
In problem 6C.17 from the textbook, it asks "which is the stronger base, the hypobromite ion BrO- or morphine C17H19O3N." Why is the hypobromite ion the stronger base?
- Sat Dec 07, 2019 12:25 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Polydentates and Chelates
- Replies: 4
- Views: 350
Re: Polydentates and Chelates
Yes, all polydentate ligands bind to the central atom at multiple sites and can form a loop/ring which includes the central atom.
- Sat Dec 07, 2019 12:22 pm
- Forum: Air Pollution & Acid Rain
- Topic: Acid Rain & Solutions
- Replies: 4
- Views: 429
Acid Rain & Solutions
Why does rain become acidic and what are some solutions to lessening the acidity?
- Sat Dec 07, 2019 11:26 am
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Anion Stability & Acid Strength
- Replies: 1
- Views: 352
Anion Stability & Acid Strength
How does the stability of the resulting anion change as you go down a group or across a period in the periodic table?
- Fri Dec 06, 2019 2:30 pm
- Forum: Hybridization
- Topic: Hybridization from Atomic Orbitals
- Replies: 1
- Views: 48
Hybridization from Atomic Orbitals
From a conceptual standpoint, how does hybridization arise from atomic orbitals?
- Sun Dec 01, 2019 9:45 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: J.9
- Replies: 2
- Views: 167
Re: J.9
We can assume strong acids/bases will completely dissociate in water, whereas very few ions will be found in a weak acids/base solution.
- Sun Dec 01, 2019 9:40 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Weak acids & pH
- Replies: 4
- Views: 201
Weak acids & pH
How does the solvent play a role in the pH of a weak acid solution?
- Sun Dec 01, 2019 9:35 pm
- Forum: Polyprotic Acids & Bases
- Topic: Oxoacids Trends
- Replies: 1
- Views: 227
Oxoacids Trends
Why does the strength of the acid increase for an oxoacid when the oxidation number of the central atom increases?
- Sun Dec 01, 2019 9:23 pm
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Ka & Entropy
- Replies: 1
- Views: 52
Ka & Entropy
How does the Ka/Kb value depend on entropy and enthalpy?
- Sun Dec 01, 2019 2:17 pm
- Forum: Bronsted Acids & Bases
- Topic: Bases & Coordinate Covalent Bonds
- Replies: 2
- Views: 198
Bases & Coordinate Covalent Bonds
When an O2- ion in solution takes a proton from a water molecule, does the H2O molecule act as a strong or weak acid? Why is the bond between the proton and lone pair of electrons on O2- a coordinate covalent bond?
- Sun Nov 24, 2019 12:46 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Bronsted vs. Lewis Acids
- Replies: 9
- Views: 487
Bronsted vs. Lewis Acids
What is the difference between the Bronsted and Lewis definitions of acids/bases and which definition includes more acids?
- Sun Nov 24, 2019 12:42 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordination Compounds
- Replies: 3
- Views: 162
Re: Coordination Compounds
Coordination compounds have a central atom/ion bonded by coordinate covalent bonds to other molecules/ions.
- Sun Nov 24, 2019 12:31 pm
- Forum: Naming
- Topic: Polydentate Ligands
- Replies: 2
- Views: 80
Polydentate Ligands
What does it mean for a ligand to be polydentate? What would it look like and how would it affect the shape/naming of the compound?
- Sun Nov 24, 2019 12:27 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Oxidation states
- Replies: 6
- Views: 380
Oxidation states
How are oxidation states determined in coordination complexes?
- Sun Nov 24, 2019 10:53 am
- Forum: Hybridization
- Topic: Hybridization Notation
- Replies: 5
- Views: 371
Re: Hybridization Notation
Yes, sp^3d would be the correct notation.
- Sat Nov 16, 2019 11:44 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Determining if a molecule is polar or non polar
- Replies: 9
- Views: 843
Re: Determining if a molecule is polar or non polar
We don't have to determine polarity of the molecule using exact electronegativity values. We can determine if a bond is polar/nonpolar using trends from the periodic table. If polar bonds cause dipoles and don't cancel out in a molecule, it will be polar. If the dipoles do cancel out, the molecule w...
- Sat Nov 16, 2019 11:33 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone pairs
- Replies: 3
- Views: 180
Lone pairs
Why do lone pairs of electrons occupy a greater amount of space (and cause more repulsion) than bonded electron pairs?
- Sat Nov 16, 2019 11:31 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR Notation
- Replies: 5
- Views: 280
Re: VSEPR Notation
A is the central atom, X's subscript refers to the number of bonding electron pairs around the central atom, and E's subscript refers to the number of lone electron pairs on the central atom.
- Sat Nov 16, 2019 11:29 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Symmetry and Polarity
- Replies: 13
- Views: 921
Re: Symmetry and Polarity
The 2D representation of the Lewis structure may not accurately represent the molecule's shape. Symmetry can be determined after determining the molecule's VSEPR shape.
- Sat Nov 16, 2019 11:26 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Deciding Between Trigonal Planar vs Trigonal Pyramidal
- Replies: 4
- Views: 174
Re: Deciding Between Trigonal Planar vs Trigonal Pyramidal
You first look at the number of regions of electron density around the central atom. In the trigonal planar shape, there are 3 bonding electron pairs around the central atom. In the trigonal pyramidal shape, there are 4 regions of electron density around the central atom, but the shape is not tetrah...
- Sun Nov 10, 2019 9:41 pm
- Forum: Resonance Structures
- Topic: Resonance Hybrids
- Replies: 3
- Views: 168
Re: Resonance Hybrids
The actual structure of the molecule is a hybrid of all possible resonance structures- after drawing all possible resonance structures, you can just draw arrows to indicate that the actual structure is actually an average of all these structures.
- Sun Nov 10, 2019 9:30 pm
- Forum: Electronegativity
- Topic: Ionization energy and electronegativity
- Replies: 8
- Views: 751
Re: Ionization energy and electronegativity
The trends for ionization energy and electronegativity in the periodic table increase across a period and down a group. Ionization energy is the energy it takes to remove a valence electron from an atom. Electronegativity measures how much the atom is able to attract electrons.
- Sun Nov 10, 2019 9:26 pm
- Forum: Electronegativity
- Topic: dipole moments
- Replies: 7
- Views: 284
Re: dipole moments
Larger differences in electronegativity lead to larger dipole moments (the electrons are pulled towards the atom with higher electronegativity).
- Sun Nov 10, 2019 9:21 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: formal charge
- Replies: 7
- Views: 418
Re: formal charge
If a molecule can potentially have multiple possible structures, it is a good idea to calculate the formal charge of each atom so that you are drawing the lowest energy structure possible.
- Sun Nov 10, 2019 9:17 pm
- Forum: Octet Exceptions
- Topic: incomplete octet
- Replies: 6
- Views: 452
Re: incomplete octet
H, Li, and Be all form duplets in Lewis structures to achieve the noble gas configuration of He. B also has an incomplete octet of 6 electrons (like in the compound BF3) because F is unlikely to share more electrons with boron due to its high electronegativity.
- Sun Nov 03, 2019 3:55 pm
- Forum: Dipole Moments
- Topic: Polarity
- Replies: 4
- Views: 150
Re: Polarity
You can compare the electronegativity of the elements using the periodic table- there will be a greater electron density around the element with a higher electronegativity.
- Sun Nov 03, 2019 3:46 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizability
- Replies: 3
- Views: 246
Re: Polarizability
For cations, polarizing power decreases down a group and increases across a period (it is highest for small, highly charged cations). For anions, their polarizability increases down a group and decreases across a period (highest for larger anions).
- Sun Nov 03, 2019 3:39 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Expanded Octet for Lowest Formal Charge
- Replies: 2
- Views: 103
Re: Expanded Octet for Lowest Formal Charge
Atoms in period 3 and beyond can have expanded octets. In order to make each atom's formal charge as close as possible to 0 (and find the lowest energy molecule) we can use expanded octets if necessary.
- Sun Nov 03, 2019 1:02 pm
- Forum: Electronegativity
- Topic: Noble Gases and Electronegativity
- Replies: 3
- Views: 289
Re: Noble Gases and Electronegativity
Electronegativity increases across a period in the periodic table, with the exception of noble gases, which have no electronegativity because of their complete octet.
- Sun Nov 03, 2019 12:53 pm
- Forum: Lewis Structures
- Topic: Lewis Structures for ionic compounds
- Replies: 2
- Views: 67
Re: Lewis Structures for ionic compounds
Ionic compounds can also be drawn as Lewis structures- with compounds that have mostly ionic character (like NaCl) you could draw the lone pair electrons as belonging to Cl rather than being shared. The compound would be written as two separate ions, Na+ and Cl-
- Sun Oct 27, 2019 8:50 pm
- Forum: Lewis Structures
- Topic: Expanded valence shells
- Replies: 3
- Views: 74
Re: Expanded valence shells
Yes, elements from period 3 onwards will have expanded valence shells because the octet rule applies only to the s and p blocks of the periodic table.
In PCl5, P forms five bonds (10 shared electrons) as it is bonded to 5 atoms of Cl.
In PCl5, P forms five bonds (10 shared electrons) as it is bonded to 5 atoms of Cl.
- Sun Oct 27, 2019 8:43 pm
- Forum: Ionic & Covalent Bonds
- Topic: Putting valence electrons on N than H
- Replies: 2
- Views: 86
Re: Putting valence electrons on N than H
The electron configuration of hydrogen is 1s2, so it can only share 2 electrons (1 bond). Therefore the remaining valence electrons must be added to nitrogen.
- Sun Oct 27, 2019 8:41 pm
- Forum: Ionic & Covalent Bonds
- Topic: What is the difference between an anion and cation?
- Replies: 7
- Views: 830
Re: What is the difference between an anion and cation?
Anions and cations form usually between metals and nonmetals: when one atom's electronegativity is significantly higher than the other atom's so that one atom removes an electron from the other. As a result, a positive ion (cation) and a negative ion (anion) are formed. An example would be the salt ...
- Sun Oct 27, 2019 8:38 pm
- Forum: Ionic & Covalent Bonds
- Topic: HW 2A.21d
- Replies: 5
- Views: 201
Re: HW 2A.21d
Ag is one of the exceptions to the usual electron configuration pattern. Since a full d-shell is much more stable than a partially full d-shell (d9), the electron configuration becomes [Kr]4d10 5s1.
- Sun Oct 27, 2019 8:33 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ionic and Covalent Bonds and Electrons
- Replies: 3
- Views: 140
Re: Ionic and Covalent Bonds and Electrons
In an ionic bond, one atom removes an electron from another atom, so you will be more likely to find an electron near the more electronegative atom (anion). Covalent bonds can either be polar or nonpolar- in polar covalent bonds, it is more likely to find an electron near the more electronegative at...
- Sat Oct 19, 2019 9:49 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Inner e- and Outer e-
- Replies: 14
- Views: 451
Re: Inner e- and Outer e-
In multi-electron atoms, outer electrons experience less electrostatic attraction to the nucleus than the inner electrons do because of the shielding effect. This results in the effective nuclear charge felt by the valence (outer) electrons to be less than the inner electrons.
- Sat Oct 19, 2019 9:19 pm
- Forum: Photoelectric Effect
- Topic: One photon one atom interaction
- Replies: 14
- Views: 533
Re: One photon one atom interaction
Increasing the frequency of the light after the threshold energy has already been surpassed would increase the KE of the ejected electron. Increasing the intensity of the light (proportional to the number of photons) would increase the number of electrons ejected, because of the one photon-one elect...
- Sat Oct 19, 2019 9:10 pm
- Forum: Properties of Light
- Topic: Problem 1.27
- Replies: 2
- Views: 170
Re: Problem 1.27
Given the frequency of the light as 6.27 * 10^14 Hz, you can use the equation c=v(wavelength) to calculate the wavelength of the light. For part b, given the wavelength as 421 nm you can calculate the frequency using the same c=v (wavelength) equation.
- Sat Oct 19, 2019 8:47 pm
- Forum: Properties of Light
- Topic: Difference between photon vs particle
- Replies: 5
- Views: 518
Re: Difference between photon vs particle
Photons refer to a specific type of particle- the discrete packets of light energy. In certain behaviors of light (like the photoelectric effect) the photons of light behave like general particles, whereas some of its other behaviors (diffraction) are wavelike.
- Sat Oct 19, 2019 8:18 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: n, l, m
- Replies: 4
- Views: 169
Re: n, l, m
"n" is the principal quantum number, which defines the size and energy of the orbital. "l" indicates the orbital's shape (s, p, d, or f) or its angular momentum (how 'fast' the electron moves around the nucleus). "m" tells us the electron's orientation in the orbital. W...
- Sun Oct 13, 2019 9:45 am
- Forum: Photoelectric Effect
- Topic: Question from module
- Replies: 5
- Views: 185
Re: Question from module
The kinetic energy of an electron is its mass x velocity. You can use the mass of an electron to find the KE, which is 9.11 x 10^-31 kg (the mass of an electron will be given to us on tests).
- Sun Oct 13, 2019 9:29 am
- Forum: Properties of Light
- Topic: de broglies equation
- Replies: 6
- Views: 294
Re: de broglies equation
De Broglie's equation (wavelength = h/p) shows the relationship between wavelength and momentum (mass x velocity). The equation can be used to calculate the wavelength of a particle that is small enough to have wavelike properties. The wavelength will also be more dependent on the mass of the partic...
- Sun Oct 13, 2019 9:02 am
- Forum: Properties of Light
- Topic: Light's Behavior
- Replies: 3
- Views: 266
Re: Light's Behavior
At the larger scale, light appears to be continuous like a wave, but when light is observed as the microscopic scale, it is actually made up of a stream of discrete photons. Certain behaviors of light are characteristic of waves (diffraction patterns) and other behaviors are characteristic of partic...
- Sat Oct 12, 2019 4:54 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: G5
- Replies: 2
- Views: 383
Re: G5
You can use the given mass of the solid and the volume of the water added to calculate the molarity of the sodium carbonate solution, which is 0.07967 M. In sodium carbonate there is a 2:1 mole ratio of Na+ to Na2CO3. Then you can use the M1V1=M2V2 equation can be used to calculate the volumes of ea...
- Tue Oct 08, 2019 10:24 pm
- Forum: Empirical & Molecular Formulas
- Topic: Estimating the greatest mass percentage
- Replies: 2
- Views: 139
Re: Estimating the greatest mass percentage
Yes, in nitric acid (NO3), if you have an approximate idea of the atomic masses of N and O you can estimate which element will have the greatest mass percentage by comparing the ratio of N to O atoms.
- Thu Oct 03, 2019 5:00 pm
- Forum: Balancing Chemical Reactions
- Topic: H.1 Chemical Principle 7th edition
- Replies: 4
- Views: 193
Re: H.1 Chemical Principle 7th edition
We can't add O to the equation because oxygen is not one of the products produced in this chemical reaction.
The correctly balanced equation would be 2Cu + SO2 --> 2CuO + S.
The correctly balanced equation would be 2Cu + SO2 --> 2CuO + S.
- Thu Oct 03, 2019 4:57 pm
- Forum: Balancing Chemical Reactions
- Topic: Fundamentals L39
- Replies: 2
- Views: 133
Re: Fundamentals L39
We find the identity of the oxide by using the known masses to determine the empirical formula of the oxide. We know that the mass of the crucible and product together is 28.35 g, so the mass of the total product is 1.9 g. The mass of tin (Sn) in the product is 1.50 g so we know the mass of O in the...
- Thu Oct 03, 2019 4:48 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Molarity
- Replies: 9
- Views: 342
Re: Molarity
Molarity can be determined by dividing the moles of solute by the volume (in liters) of solution; molarity essentially just represents how concentrated a particular solution is.
- Thu Oct 03, 2019 4:34 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Avogadro's Number
- Replies: 8
- Views: 588
Re: Avogadro's Number
Yes, Avogadro's number represents the number of objects, in this case, atoms, in 1 mole. For problem E7, you divide the given number of atoms (2.1 x 10^9) by Avogadro's number (6.022 x 10^23) to determine the number of moles of carbon present.
- Thu Oct 03, 2019 4:26 pm
- Forum: Empirical & Molecular Formulas
- Topic: Law of Conservation of Mass?
- Replies: 4
- Views: 423
Re: Law of Conservation of Mass?
The Law of Conservation of Mass tells us that no mass is lost or gained in a chemical reaction (total mass of reactants = total mass of products). In this problem the total mass of reactants is 12g, while the mass of the product is 14g, so this reaction is not possible.