## Search found 63 matches

Mon Mar 11, 2019 1:47 am
Forum: First Order Reactions
Topic: stoichiometry
Replies: 2
Views: 101

### 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: 97

### 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: 120

### 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: 59

### 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: 98

### 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: 130

### 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: 103

### 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: 81

### 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: 59

### 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: 40

### 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: 51

### 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: 113

### 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: 263

### 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: 73

### 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: 581

### 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: 126

### 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: 283

### 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: 66

### 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: 127

### 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: 132

### 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: 84

### 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: 93

### 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: 112

### 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
Replies: 2
Views: 82

### 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: 324

### 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: 258

### 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: 72

### 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: 65

### 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: 86

### 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: 330

### 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: 73

### 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: 74

### 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: 117

### 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: 68

### 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: 46

### 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: 53

### 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: 67

### 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: 90

### 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: 62

### 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: 256

### 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: 54

### 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: 157

### 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: 53

### 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: 259

### 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: 200

### 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: 403

### 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: 253

### 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: 205

### 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: 81

### 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: 50

### 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: 154

### 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: 28

### 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: 118

### 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: 76

### 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: 54

### 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: 74

### 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: 325

### 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: 57

### 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: 143

### 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: 143

### 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: 140

### 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: 258

### 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: 68

### 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.