Search found 63 matches
- Mon Mar 11, 2019 1:47 am
- Forum: First Order Reactions
- Topic: stoichiometry
- Replies: 2
- Views: 290
Re: stoichiometry
For those problems, you have to set up an ICE box in order to find your final concentrations of [A] given the change in concentration of [B] so that you can plug it into the integrated rate laws for the respective orders.
- Mon Mar 11, 2019 1:44 am
- Forum: First Order Reactions
- Topic: 15.23 c) Determining rate constant
- Replies: 2
- Views: 322
Re: 15.23 c) Determining rate constant
You have to set up an ICE box to find your final value of [A] based on the change of [B] given. Then you plug it into the first order integrated rate law to find your rate constant.
- Mon Mar 11, 2019 1:40 am
- Forum: General Rate Laws
- Topic: Order of rxns and stoichiometric coefficients
- Replies: 3
- Views: 340
Re: Order of rxns and stoichiometric coefficients
It is a possibility that they could be the same, but the stoichiometric coefficients don't actually correspond to the reaction order.
- Mon Mar 11, 2019 1:37 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Rate and equilibrium constant
- Replies: 1
- Views: 254
Re: Rate and equilibrium constant
The equilibrium constant for a one-step reaction is equal to the forward rate constant divided by the reverse rate constant. Rate constant is the rate of conversion of reactants to products, while equilibrium constant is the ratio of concentration of products to concentration of reactants.
- Mon Mar 11, 2019 1:31 am
- Forum: Balancing Redox Reactions
- Topic: Balancing redox rxns in basic solution
- Replies: 2
- Views: 315
Re: Balancing redox rxns in basic solution
You have to neurtralize the H+ ions by adding OH- ions for every H+ ions onto both sides of the equation. Once you have combined your 2 half-reactions, you can add the OH- ions to both sides depending on the number of H+ ions on each side.
- Thu Mar 07, 2019 11:03 pm
- Forum: General Rate Laws
- Topic: 15.3
- Replies: 3
- Views: 438
Re: 15.3
You use the average rate of rxn equation where you do -delta(R)/delta(t). And then you look at the coefficients to find the ratios and the rates of each compound.
- Thu Mar 07, 2019 11:01 pm
- Forum: General Rate Laws
- Topic: 15.1
- Replies: 3
- Views: 333
Re: 15.1
You have to look at the coefficient, Joseph. The rate of consumption of N2 is 1/3 times the rate of consumption of H2 because it is a 1:3 ratio.
- Thu Mar 07, 2019 10:55 pm
- Forum: First Order Reactions
- Topic: Question 15.27
- Replies: 1
- Views: 271
Question 15.27
A substance A decomposes in a first-order reaction and its half life is 355 s. How much time must elapse for the concentration of A to decrease to (a) (1/8)[A]0 I plugged in the values to the integrated rate law equation for first order reactions but I got 30.36 mins and I'm not sure where I went wr...
- Tue Feb 26, 2019 7:32 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.13b 6th edition
- Replies: 1
- Views: 211
14.13b 6th edition
When you're writing the cell diagram for this problem, why do you have to add Pt(s) to the anode side of the cell diagram if there is a solid on that side? The solution says "Pt(s)|I-(aq)|I2(s)...". Under what conditions do you have to add Pt(s)?
- Tue Feb 26, 2019 7:01 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 14.11d 6th edition
- Replies: 1
- Views: 213
14.11d 6th edition
I'm confused on how to set up the half reaction for the anode (O2 and H+). Which molecules should go on which sides and what should be balanced first?
- Tue Feb 26, 2019 3:36 pm
- Forum: Balancing Redox Reactions
- Topic: Question 14.1c 6th edition
- Replies: 1
- Views: 211
Question 14.1c 6th edition
For part c, the solution says that the H(aq) of the reduction half-reaction has a negative charge. Is this a typo and if not, why is this so? I thought we are supposed to add H+ to balance the Hs in the half-reaction.
- Fri Feb 22, 2019 12:14 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs free energy at phase changes
- Replies: 2
- Views: 332
Gibbs free energy at phase changes
Why is Gibbs free energy change zero at phase changes, like boiling points, that are done at constant T and P? Or is that not always the case?
- Fri Feb 22, 2019 12:12 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Delta G=0 at equilibrium
- Replies: 4
- Views: 2489
Delta G=0 at equilibrium
I understand that at equilibrium, Gibbs free energy change is zero but I'm confused on the conceptual reasoning behind this. Could someone explain this to me?
- Fri Feb 22, 2019 12:09 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Question 9.63
- Replies: 2
- Views: 324
Question 9.63
"Determine which of the following compounds are stable with respect to decomposition into their elements under standard conditions at 25 &C (see Appendix 2A): (a) PCl5(g); (b) HCN(g); (c) NO(g); (d) SO2(g). " How do I determine stability based off of Gibbs free energy values?
- Thu Feb 14, 2019 2:59 pm
- Forum: Calculating Work of Expansion
- Topic: S=0
- Replies: 12
- Views: 1692
Re: S=0
A system at equilibrium has no tendency to change in either the forward or reverse direction so it would have an entropy of 0.
- Thu Feb 14, 2019 2:51 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Molar and specific heat capacity
- Replies: 3
- Views: 395
Re: Molar and specific heat capacity
Also, molar and specific heat capacity are both intensive properties, while heat capacity is an extensive property.
- Thu Feb 14, 2019 2:44 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Cp,m
- Replies: 3
- Views: 680
Re: Cp,m
Also, you use Cv,m and Cp,m to find heat capacities and by using the equation Cp,m= Cv,m +R, you can find the value of each other depending on the type of molecule. For example, the Cv,m of linear molecules is (5/2)*R, so the Cp,m of linear molecules is (7/2)*R.
- Thu Feb 07, 2019 10:15 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Question 8.67 b
- Replies: 1
- Views: 183
Question 8.67 b
"Use the information in Tables 8.3, 8.6, and 8.7 to estimate the enthalpy of formation of each of the following compounds in the liquid state. The standard enthalpy of sublimation of carbon is +717 kJ·mol-1. (a) H2O; (b) methanol, CH3OH; (c) benzene, C6H6 (without resonance); (d) benzene, C6H6 ...
- Thu Feb 07, 2019 10:09 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Work
- Replies: 3
- Views: 404
Re: Work
Work is positive if work is done by the system and it's negative if work is done on the system.
- Thu Feb 07, 2019 10:07 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Molar Heat Capacity
- Replies: 3
- Views: 441
Re: Molar Heat Capacity
Molar heat capacity is greater at constant pressure than at constant volume because at constant P, some of the heat goes into expansion work which means there will be less energy left over to raise the temperature unlike at constant V, where no expansion work is done so all the energy goes into rais...
- Fri Feb 01, 2019 1:09 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Question 8.3 6th edition
- Replies: 2
- Views: 235
Question 8.3 6th edition
"Air in a bicycle pump is compressed by pushing in the handle. If the inner diameter of the pump is 3.0 cm and the pump is depresses 20 cm with a pressure of 2.00 atm, how much work is done in the compression? I know I need to use w=-p(delta(v)) to find work, but I'm not sure how to find volume...
- Fri Feb 01, 2019 1:05 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Enthalpy vs Internal energy
- Replies: 5
- Views: 536
Enthalpy vs Internal energy
What is the difference between the enthalpy of a system and the internal energy of a system?
- Fri Feb 01, 2019 12:17 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Reversible and isothermal
- Replies: 2
- Views: 364
Reversible and isothermal
Can someone explain what it means if a reaction is reversible and isothermal?
- Wed Jan 23, 2019 9:40 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Question about problem 6D.15(b)
- Replies: 2
- Views: 229
Re: Question about problem 6D.15(b)
Al3+ cations become hydrated by water molecules that act as Bronsted acids when they are placed in water so Al3+ will become Al(H2O)6 as seen in Table 12.8. Metal cations usually have 6H2O molecules attached to it. That will be used as your acid and you can set up the equation such that Al(H2O)6+H2O...
- Wed Jan 23, 2019 9:33 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Writing equations for weak acids/bases
- Replies: 3
- Views: 581
Writing equations for weak acids/bases
Is it acceptable to write the short-handed versions of weak acid and weak base equations where HA-->(H+)+(A-) and B+H2O-->(HB+)+(OH-), respectively, or should we always write out the full equation and include all spectator ions?
- Wed Jan 23, 2019 9:27 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: 6th edition 12.45
- Replies: 1
- Views: 449
6th edition 12.45
"Arrange the following bases in order of increasing strength on the basis of the pKa values of their conjugate acids, which are given in parentheses: (a) ammonia (9.26); (b) methylamine (10.56); (c) ethylamine (10.81); (d) aniline (4.63) (see Exercise 12.44). Is there a simple pattern of streng...
- Wed Jan 16, 2019 11:12 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Effect of Pressure [ENDORSED]
- Replies: 2
- Views: 189
Effect of Pressure [ENDORSED]
I learned in high school that when pressure increases in a reaction, equilibrium will shift towards the side with less moles of gas (i.e. 3H2+N2->2NH3; shift to the right), but a lot of the problems I've encountered have equal moles on both sides. How should I think of the effect of pressure on the ...
- Wed Jan 16, 2019 11:01 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Question 11.35 6th edition
- Replies: 1
- Views: 158
Re: Question 11.35 6th edition
To find Ka, you take 10^(-pKa). And to find pKa, you take -log(Ka).
- Wed Jan 16, 2019 10:55 pm
- Forum: Ideal Gases
- Topic: 6th edition 11.81
- Replies: 2
- Views: 327
6th edition 11.81
"A reactor for the production of ammonia by the Haber process is found to be at equilibrium with PN2 " 3.11 bar, PH2 " 1.64 bar, and PNH3 " 23.72 bar. If the partial pressure of N2 is increased by 1.57 bar, what will be the partial pressure of each gas once equilibrium is re-esta...
- Wed Jan 09, 2019 8:36 pm
- Forum: Ideal Gases
- Topic: Units
- Replies: 19
- Views: 1071
Re: Units
When you're using PV=nRT, the temperature should always be in Kelvin units not Celsius.
- Wed Jan 09, 2019 8:35 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Q vs. K
- Replies: 2
- Views: 367
Re: Q vs. K
When Q=K, it means that the reaction is at equilibrium and there is no shift to either the reactants or products.
- Tue Jan 08, 2019 5:13 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K vs. Q
- Replies: 2
- Views: 170
K vs. Q
What is the difference between K, the equilibrium constant, and Q, the reaction quotient? I know they are both solved for in the same way, but I'm confused on how they are different and what Q shows.
- Fri Dec 07, 2018 11:23 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Chem 6th Edition 12.25
- Replies: 2
- Views: 293
Re: Chem 6th Edition 12.25
Kw stands for the equilibrium constant for water and can be used to find the concentration of H+ ions if given the concentration of OH- ions and vice versa. The formula is Kw= [H+][OH-]= 1*10^-14 which is derived from pH+pOH=14. Once you find your concentration of OH- from Ba(OH)2, you can plug it i...
- Mon Dec 03, 2018 5:59 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: Question 12.19 6th edition
- Replies: 1
- Views: 228
Question 12.19 6th edition
For this question, it asks you to find the difference in pH values between two solutions after dilution by 12% of the initial solution. How should I start this problem?
- Mon Dec 03, 2018 4:07 pm
- Forum: Conjugate Acids & Bases
- Topic: Charges of conjugate acids and bases
- Replies: 1
- Views: 259
Charges of conjugate acids and bases
When finding the conjugate bases or acids in an equation, are we going to be expected to know and memorize the charges of the compounds and if so, what is an easy way to learn them? For example, if CH6H5OH is the acid and the conjugate base is C6H5O-, and if H2PO4- is the acid then the conjugate bas...
- Wed Nov 28, 2018 5:35 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 7th Edition 3.19b
- Replies: 1
- Views: 177
Re: 7th Edition 3.19b
Yes so you would attach the two CH3 molecules to either side of the central atom Be and then you can find the shape for the C atoms and Be atom which should be tetrahedral and linear, respectively.
- Wed Nov 28, 2018 5:32 pm
- Forum: Hybridization
- Topic: Question 4.31 6th edition
- Replies: 1
- Views: 201
Question 4.31 6th edition
I'm confused on how to answer this question. They ask you to state the relative orientations of hybrid orbitals, but I'm not sure how to describe the positions in terms of the molecular shape.
- Wed Nov 28, 2018 5:19 pm
- Forum: Hybridization
- Topic: 4.43 Increasing s-character of hybrids
- Replies: 2
- Views: 205
Re: 4.43 Increasing s-character of hybrids
If you look at sp3, you see that the s character is 25% and the p character is 75% and if you look at sp2, you see that the s character is 33.3% and the p character is 66.6%. sp3 hybridization has bond angles of 109.5 degrees, while sp2 hybridization has bond angles of 120 degrees. So you can see th...
- Tue Nov 20, 2018 3:57 pm
- Forum: Hybridization
- Topic: S and p character effect on bonds
- Replies: 2
- Views: 351
S and p character effect on bonds
How do s and p character affect bond length and bond strength in hybrid orbitals?
- Tue Nov 20, 2018 3:50 pm
- Forum: Hybridization
- Topic: Test 3
- Replies: 8
- Views: 798
Re: Test 3
Yes I believe so. I'm pretty sure the test will cover the last parts of bonding like bond strengths and lengths, and electronegativity and polarizability as well as all of molecular shape and structure outline stuff.
- Mon Nov 19, 2018 6:30 pm
- Forum: Hybridization
- Topic: Relation to Bond Angles
- Replies: 3
- Views: 272
Relation to Bond Angles
How is hybridization related to bond angles and how do lone pairs factor into this relationship?
- Wed Nov 14, 2018 5:13 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: IMFs [ENDORSED]
- Replies: 2
- Views: 331
IMFs [ENDORSED]
Do we need to know how IMFs affect other properties like surface tension or viscosity?
- Wed Nov 14, 2018 4:55 pm
- Forum: Lewis Structures
- Topic: Question 4.19b in 6th edition
- Replies: 1
- Views: 98
Question 4.19b in 6th edition
This question asks to find the shape and bond angles for (CH3)2Be, but I'm not sure how to draw the Lewis structure for this compound. Where would the 6th hydrogen attach to?
- Wed Nov 14, 2018 4:46 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Polar v. Non Polar
- Replies: 7
- Views: 845
Re: Polar v. Non Polar
You have to look at the electronegativities. If the atoms have about the same electronegativity, then the molecule is non-polar and if the atoms have different electronegativities, then the molecule is polar because electrons are being unequally shared in the molecule.
- Tue Nov 06, 2018 2:13 pm
- Forum: Electronegativity
- Topic: Electron affinity
- Replies: 5
- Views: 569
Electron affinity
How does electron affinity change across the period table? Are there any trends?
- Tue Nov 06, 2018 2:12 pm
- Forum: Empirical & Molecular Formulas
- Topic: Assumption of 100g
- Replies: 2
- Views: 1475
Assumption of 100g
Why is it that sometimes when they give you the percent composition of each element and the molar mass, you don't assume 100 g but instead you multiply that percentage by the molar mass to find the g of each element? I thought the molar mass is only supposed to be used when solving for the molecular...
- Tue Nov 06, 2018 1:58 pm
- Forum: Octet Exceptions
- Topic: Octet rule vs. Formal charge
- Replies: 7
- Views: 1012
Re: Octet rule vs. Formal charge
Not all elements can hold more than an octet, but when you're dealing with the ones that can like S and P, if the formal charge of the elements would be closer to 0 after breaking the octet rule, then you should break the octet.
- Tue Oct 30, 2018 10:06 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Finding the lowest energy structure
- Replies: 5
- Views: 597
Finding the lowest energy structure
When you are trying to identify the structure of lower energy between two lewis structures, do you always have to test each atom's formal charge to know which compound to pick?
- Tue Oct 30, 2018 10:00 pm
- Forum: Ionic & Covalent Bonds
- Topic: 3.41 6TH EDITION
- Replies: 1
- Views: 136
Re: 3.41 6TH EDITION
I would begin with first finding the central atom for each compound given and then the total number of valence electrons for each compound as well.
- Tue Oct 30, 2018 9:53 pm
- Forum: Lewis Structures
- Topic: Question 3.41c for 6th edition
- Replies: 1
- Views: 122
Question 3.41c for 6th edition
For this question, we're supposed to write out the lewis structure for glycine (H2C(NH2)COOH)) and I know that the C atoms should be the central atoms, but how do we know where the other atoms are supposed to bond to? Is it just like guess and check until the electrons equal the total valence electr...
- Tue Oct 23, 2018 7:37 pm
- Forum: DeBroglie Equation
- Topic: DeBroglie Equation Post Assessment
- Replies: 3
- Views: 320
Re: DeBroglie Equation Post Assessment
By plugging in your given wavelength, the mass of an electron (9.11E-31kg), and Planck's constant, you can solve for the velocity.
- Tue Oct 23, 2018 7:13 pm
- Forum: Trends in The Periodic Table
- Topic: Question 2.67 6th edition
- Replies: 1
- Views: 48
Question 2.67 6th edition
Does anyone know why carbon has a higher electron affinity than nitrogen for part b? I thought electron affinity increases as you travel from left to right of a period and from bottom to top of a group since there is a stronger nuclear attraction as more electrons are added on.
- Tue Oct 23, 2018 3:20 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Question 2.43 6th Edition
- Replies: 2
- Views: 354
Question 2.43 6th Edition
For this problem they ask you to write out the ground-state electron configuration of different elements given. Does anyone know why silver is written as [Kr](4d^10)(5s^1) and not as [Kr](5s^2)(4d^9)?
- Wed Oct 17, 2018 3:36 pm
- Forum: DeBroglie Equation
- Topic: 1.37
- Replies: 1
- Views: 148
Re: 1.37
There is actually no difference in their wavelengths and they both have a wavelength of 1.44 pm since they have the same mass and velocity so you can just disregard that part of the question.
- Tue Oct 16, 2018 8:03 pm
- Forum: Properties of Light
- Topic: 6th Edition 1.13(a)
- Replies: 2
- Views: 143
Re: 6th Edition 1.13(a)
n1 should always be your initial and n2 should be your final quantum level.
- Tue Oct 16, 2018 3:31 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Calculating Electron Transmission for H-atom
- Replies: 2
- Views: 280
Re: Calculating Electron Transmission for H-atom
So since the equation has a denominator of n^2, you take the initial n value which is four (initial quantum level) and square it so you get -1/16 and then you take the final n value which is two (final quantum level) and square that also so you get -1/4.
- Wed Oct 10, 2018 12:13 am
- Forum: Properties of Light
- Topic: Light
- Replies: 9
- Views: 862
Re: Light
I'm pretty sure amplitude and frequency aren't dependent on each other since amplitude is like how high/low the wave goes and frequency is how fast the wave travels. I know that wavelength and frequency are inversely proportional of each other based on c=(wavelength)(frequency).
- Mon Oct 08, 2018 6:10 pm
- Forum: Properties of Light
- Topic: Photoelectric Effect Module #28
- Replies: 1
- Views: 65
Re: Photoelectric Effect Module #28
Yes the mass is referring to that of an electron. I think we most likely won't have to memorize that value and it'll probably be given to us if needed on an exam.
- Mon Oct 08, 2018 6:05 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Homework Problem in Section G
- Replies: 3
- Views: 287
Re: Homework Problem in Section G
Oh shoot also forgot to add that you have to multiply your final answer by 2 since there are 2 N atoms in NH4NO3. my bad.
- Mon Oct 08, 2018 6:02 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Homework Problem in Section G
- Replies: 3
- Views: 287
Re: Homework Problem in Section G
So basically you have to use the M1V1=M2V2 equation to solve this by substituting you initial molar concentration and volume of the solution prior to dilution into the left side of the equation and then substituting your final volume (4l) into the right side so that you can solve for your final mola...
- Thu Oct 04, 2018 2:53 pm
- Forum: Balancing Chemical Reactions
- Topic: Balancing Chemical Reactions with Heat
- Replies: 6
- Views: 1362
Re: Balancing Chemical Reactions with Heat
It's more just for info right now I think, but it definitely doesn't affect the balancing of the equation so you don't have to add any reactants/products. I think it's just used in thermodynamics.
- Thu Oct 04, 2018 2:23 pm
- Forum: Balancing Chemical Reactions
- Topic: H3, coefficients
- Replies: 7
- Views: 658
Re: H3, coefficients
I think it would be better to leave the equation as is rather than divide everything by 2 because even though the equation still remains balanced, it doesn't properly represent the number of molecules displayed in the diagram which is probably what the problem is looking for. So basically, use the t...
- Thu Oct 04, 2018 2:18 pm
- Forum: SI Units, Unit Conversions
- Topic: L.35
- Replies: 1
- Views: 132
Re: L.35
The back of the textbook states that 1 ton is equal to 10^3 kg so 907 kg definitely seems more accurate.