Search found 60 matches

by Diana Bibireata 1B
Thu Mar 14, 2019 11:30 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating Equilibrium Composition
Replies: 2
Views: 38

Re: Calculating Equilibrium Composition

After you find the x values, you plug it into the ice table. Only one of the values will give an answer that makes sense because the other x value will give a negative equilibrium concentration, which is not possible.
by Diana Bibireata 1B
Thu Mar 14, 2019 11:27 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: mmol vs mol
Replies: 6
Views: 169

Re: mmol vs mol

If the problem does not specify what units your answer should be in then it doesn't matter which one you use.
by Diana Bibireata 1B
Thu Mar 14, 2019 11:23 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Partial pressure Units
Replies: 2
Views: 37

Re: Equilibrium Partial pressure Units

Partial pressure is usually given in either atm or bar.
by Diana Bibireata 1B
Sat Mar 09, 2019 7:29 pm
Forum: Ideal Gases
Topic: sre
Replies: 5
Views: 100

Re: sre

The standard reaction enthalpy is just the enthalpy when all reactants and products are in their standard state at 1 atm.
by Diana Bibireata 1B
Sat Mar 09, 2019 7:24 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: catalyst/enzyme
Replies: 4
Views: 53

Re: catalyst/enzyme

A catalyst lowers the activation energy so it ends up speeding up the rate of the reaction.
by Diana Bibireata 1B
Sat Mar 09, 2019 7:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Negligible X
Replies: 3
Views: 57

Re: Negligible X

If the given K value is less than 10^-3 then you can use the approximation method where x is so small that the change it causes to the equilibrium concentration is negligible.
by Diana Bibireata 1B
Sun Mar 03, 2019 4:00 pm
Forum: Balancing Redox Reactions
Topic: Acidic vs basic solutions
Replies: 10
Views: 138

Re: Acidic vs basic solutions

For acidic solutions you balance out the oxygens by adding H2O and you balance the hydrogens by adding H+. For basic solutions you balance the oxygens by adding H2O and then you balance the hydrogens by adding H2O to the side that requires more H atoms and add the same amount of OH- to the other side.
by Diana Bibireata 1B
Sun Mar 03, 2019 3:54 pm
Forum: Van't Hoff Equation
Topic: units of T
Replies: 5
Views: 135

Re: units of T

When doing calculations you should always convert temperature into kelvins. In general just keep track of the units at all times because some of the constants on the constants and equation sheets (such as specific heat capacity) are given in celsius so be mindful of that.
by Diana Bibireata 1B
Sun Mar 03, 2019 3:46 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delta G
Replies: 5
Views: 86

Re: delta G

Delta G is the change in Gibbs free energy. The equation commonly used is: delta G = delta H - T(delta S). Gibbs free energy is also a state function.
by Diana Bibireata 1B
Sun Feb 24, 2019 12:03 pm
Forum: Balancing Redox Reactions
Topic: difference between oxidation and reduction
Replies: 8
Views: 96

Re: difference between oxidation and reduction

A loss of electrons is oxidation, a gain of electrons is reduction. If the charge increases then electrons were removed so it would be considered oxidation.
by Diana Bibireata 1B
Sun Feb 24, 2019 11:58 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Spontaneous cell reaction
Replies: 2
Views: 37

Re: Spontaneous cell reaction

A positive cell potential indicates the reaction is spontaneous as written for the given conditions.
by Diana Bibireata 1B
Sun Feb 24, 2019 11:28 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Platinum
Replies: 3
Views: 51

Re: Platinum

The textbook states that you include an inert electrode such as platinum when the electrode reaction does not include a conducting solid as a reactant or product.
by Diana Bibireata 1B
Sun Feb 17, 2019 2:38 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: calculating delta S
Replies: 4
Views: 55

Re: calculating delta S

Pressure and volume are inversely proportional so (P1/P2) = (V2/V1).
by Diana Bibireata 1B
Sun Feb 17, 2019 2:37 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: state functions and properties
Replies: 7
Views: 160

Re: state functions and properties

A state function only depends current conditions, not the path it takes to get there.
by Diana Bibireata 1B
Sun Feb 17, 2019 2:33 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Heating Curve
Replies: 3
Views: 81

Re: Heating Curve

When there is a phase change you use the equation S = qrev/T because the temperature is constant. You use S = nClnT2/T1 when the temperature does change.
by Diana Bibireata 1B
Thu Feb 07, 2019 10:20 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Work
Replies: 3
Views: 72

Re: Work

If work is done on the system, w is positive because the energy of the system has increased. If work is done by the system, w is negative because the energy of the system has decreased.
by Diana Bibireata 1B
Thu Feb 07, 2019 10:09 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated System
Replies: 4
Views: 82

Re: Isolated System

In an isolated system, matter and energy are not exchanged with the surroundings. Therefore the internal energy remains constant, so deltaU is 0.
by Diana Bibireata 1B
Thu Feb 07, 2019 10:07 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Definitions of Heat Capacities
Replies: 2
Views: 34

Re: Definitions of Heat Capacities

Heat capacity is the heat required to raise the temperature of an object by 1 degree C.
Specific heat capacity is the heat required to raise 1g of substance by 1 degree C.
Molar heat capacity is heat required to raise 1 mol of substance by 1 degree C.
by Diana Bibireata 1B
Thu Jan 31, 2019 10:30 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Surroundings
Replies: 11
Views: 126

Re: Surroundings

The system is the object of interest and the surroundings is anything else, so there is no boundary to the surroundings. Essentially the system + surroundings = universe.
by Diana Bibireata 1B
Thu Jan 31, 2019 10:25 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: closed vs isolated
Replies: 14
Views: 190

Re: closed vs isolated

In a closed system, energy can be exchanged with the surroundings. In an isolated system, neither matter nor energy can be exchanged with the surroundings.
by Diana Bibireata 1B
Thu Jan 31, 2019 10:21 am
Forum: Phase Changes & Related Calculations
Topic: Steam vs Boiling Water
Replies: 10
Views: 151

Re: Steam vs Boiling Water

In the process of phase change (in this case vaporization) the temperature doesn't change (stays at 100C). However, when making steam, there is still heat and energy being added to break the bonds, which is why steam causes severe burns.
by Diana Bibireata 1B
Fri Jan 25, 2019 9:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5%
Replies: 10
Views: 156

Re: 5%

If you use the approximation method when using an ICE table, the x value you get needs to be less than 5% of the initial concentration for this method to be valid.
by Diana Bibireata 1B
Fri Jan 25, 2019 9:28 pm
Forum: Phase Changes & Related Calculations
Topic: Modules
Replies: 17
Views: 205

Re: Modules

The modules are optional. The post assessments are pretty helpful however if you want extra practice.
by Diana Bibireata 1B
Fri Jan 25, 2019 9:26 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE table and Q
Replies: 6
Views: 193

Re: ICE table and Q

You use ICE tables to find the concentrations at equilibrium because the whole point of an ICE table is to show the initial concentration, the change in concentration, and the equilibrium concentration. To find Q you just find the ratio of products to reactants at any point during the reaction.
by Diana Bibireata 1B
Thu Jan 17, 2019 10:29 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Reaction Quotient
Replies: 8
Views: 154

Re: Reaction Quotient

Both K and Q are calculated the same way. K just describes the reaction at equilibrium and tells us whether there are more products or reactants at equilibrium. Q can be calculated at any part of the reaction and is used to determine the direction which a reaction will proceed.
by Diana Bibireata 1B
Thu Jan 17, 2019 10:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating PH of weak acids and bases
Replies: 5
Views: 74

Re: Calculating PH of weak acids and bases

Because the K value is so small you can use the approximation method. In this case the x value will be so small that you can assume the value (0.1-x) will be approximately equal to 0.1. You can use this method whenever K is less than 10^-3.
by Diana Bibireata 1B
Thu Jan 17, 2019 10:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quadratic equation and ICE box
Replies: 3
Views: 52

Re: Quadratic equation and ICE box

If the K value is very small (less than 10^-3) then you can use the approximation method where you assume that x is so small it won't make a big difference. If the x value you get is less than 5% of the initial concentration, then using the approximation method is valid. Otherwise you need to use th...
by Diana Bibireata 1B
Fri Jan 11, 2019 6:23 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Charles’s Law
Replies: 4
Views: 61

Re: Charles’s Law

Charles' Law simply states that the volume of a gas is directly proportional to the temperature if pressure stays constant.
by Diana Bibireata 1B
Fri Jan 11, 2019 6:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kp vs Kc
Replies: 6
Views: 73

Re: Kp vs Kc

Both are equally important. But keep in mind that Kp is only used for gases while Kc can be used for gases and aqueous solutions.
by Diana Bibireata 1B
Thu Jan 10, 2019 6:44 pm
Forum: Ideal Gases
Topic: Equilibrium Constant
Replies: 3
Views: 86

Re: Equilibrium Constant

The molar concentrations of solids and liquids do not change in a reaction and therefore are not used to calculate the equilibrium constant. On the other hand, both gases and aqueous solutions are used to calculate the equilibrium constant.
by Diana Bibireata 1B
Sat Dec 08, 2018 7:59 pm
Forum: Octet Exceptions
Topic: formal charge
Replies: 2
Views: 158

Re: formal charge

Formal charge is useful to find the most stable lewis structure. You want the formal charge to be 0 on all atoms but if that's not possible then usually the negative formal charge goes on the most electronegative atom.
by Diana Bibireata 1B
Sat Dec 08, 2018 7:51 pm
Forum: Trends in The Periodic Table
Topic: atomic radius
Replies: 2
Views: 171

Re: atomic radius

atomic radius is defined as half the distance between the centers of neighboring atoms
by Diana Bibireata 1B
Sat Dec 08, 2018 7:47 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: types of bonds
Replies: 1
Views: 112

Re: types of bonds

yes! a single bond has 1 sigma bond, a double bond has 1 sigma and 1 pi bond, and a triple bond has 1 sigma and 2 pi bonds.
by Diana Bibireata 1B
Sun Dec 02, 2018 5:05 pm
Forum: Hybridization
Topic: Hybridization
Replies: 11
Views: 147

Re: Hybridization

A trigonal planar molecule has 3 regions of electron density. the regions of electron density is equal to the number of hybrid orbitals. Therefore a trigonal planar molecule has a hybridization of sp2 (a hybrid of 1 s orbital and 2 p orbitals).
by Diana Bibireata 1B
Sun Dec 02, 2018 4:57 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted vs. Lewis
Replies: 3
Views: 73

Re: Bronsted vs. Lewis

A bronsted acid is a proton donor and a bronsted base is a proton acceptor. A lewis acid accepts an electron pair and a lewis base donates the electron pair. Both essentially mean the same thing however the lewis definition is a little more general. In the example: NH3 + H2O → NH4+ + OH- a hydrogen ...
by Diana Bibireata 1B
Sun Dec 02, 2018 4:35 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Model
Replies: 5
Views: 101

Re: VSEPR Model

when using the VSEPR model, you can essentially use the lewis structure to see how many lone and bonding pair electrons there are around the central atom to determine the AXE formula. From there you can describe shape, bond angles, polarity etc.
by Diana Bibireata 1B
Sun Nov 25, 2018 9:32 pm
Forum: Bond Lengths & Energies
Topic: Why Are Double Bonds Shorter
Replies: 3
Views: 57

Re: Why Are Double Bonds Shorter

Its because the additional bonding electrons in a double bond attract the nuclei more strongly and pull the atoms closer together.
by Diana Bibireata 1B
Sun Nov 25, 2018 9:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: e- Density
Replies: 4
Views: 82

Re: e- Density

The electrons in double and triple bonds stay together and repel other bonds/lone pairs as a single unit so you treat it as just one region of electron density.
by Diana Bibireata 1B
Sun Nov 25, 2018 2:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Dipoles
Replies: 2
Views: 54

Re: Dipoles

When there is a difference between the electronegativity of two atoms a partial charge forms. The atom with more pulling power has a greater share of electrons so it has a negative partial charge which means it has a negative dipole.
by Diana Bibireata 1B
Thu Nov 15, 2018 6:05 pm
Forum: SI Units, Unit Conversions
Topic: VSEPR model
Replies: 5
Views: 251

Re: VSEPR model

The VSEPR model accounts for bond angles and molecular shape. Regions of high electron concentration in a molecule repel one another so these regions move as far as possible to minimize repulsions.
by Diana Bibireata 1B
Thu Nov 15, 2018 5:57 pm
Forum: Dipole Moments
Topic: Dipoles
Replies: 2
Views: 48

Re: Dipoles

When there is a difference between the electronegativity of two atoms a partial charge forms. The atom with more pulling power has a greater share of electrons so it has a negative partial charge which means it has a negative dipole.
by Diana Bibireata 1B
Thu Nov 15, 2018 5:44 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR model
Replies: 3
Views: 70

Re: VSEPR model

A multiple bond is just treated as one region of electron density. The electrons in double and triple bonds stay together and repel other bonds/lone pairs as a single unit.
by Diana Bibireata 1B
Sun Nov 11, 2018 1:24 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: trigonal pyramidal
Replies: 3
Views: 59

Re: trigonal pyramidal

In the trigonal pyramidal molecular shape there are three bonds and one lone pair on the central atom. This is the best shape because the lone pair on the central atom distorts the molecular shape to reduce lone pair-bonding pair repulsions. I'm sure this will be covered more in future lectures!
by Diana Bibireata 1B
Sun Nov 11, 2018 1:11 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: Greater polarizability of larger molecules
Replies: 6
Views: 90

Re: Greater polarizability of larger molecules

In larger atoms the outermost electrons are less tightly held because the nucleus exerts a weak control over these electrons. Therefore they are easily distorted.
by Diana Bibireata 1B
Sat Nov 10, 2018 4:42 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizability
Replies: 4
Views: 122

Re: Polarizability

In larger atoms, electrons are less tightly held because they are further from the nucleus which is why they are easily distorted
by Diana Bibireata 1B
Thu Nov 01, 2018 10:22 pm
Forum: Properties of Light
Topic: Midterm Question 5a
Replies: 4
Views: 141

Re: Midterm Question 5a

The electrons in the Hg atom have discrete energy values so they can only emit certain wavelengths of light.
by Diana Bibireata 1B
Thu Nov 01, 2018 10:17 pm
Forum: Bond Lengths & Energies
Topic: Lengths of Bonds
Replies: 9
Views: 170

Re: Lengths of Bonds

The book states that "multiple bonds are shorter than single bonds between the same two elements because the additional bonding electrons attract the nuclei more strongly and pull the atoms closer together" (7th ed. pg 100)
Hope this helps!
by Diana Bibireata 1B
Thu Nov 01, 2018 10:02 pm
Forum: Lewis Structures
Topic: Lewis Structure of Glycine
Replies: 1
Views: 23

Re: Lewis Structure of Glycine

It is one of the homework problems and I think anything that shows up on the homework is fair game for the test.
by Diana Bibireata 1B
Thu Oct 25, 2018 9:38 pm
Forum: Properties of Light
Topic: Electromagnetic Spectrum
Replies: 5
Views: 149

Re: Electromagnetic Spectrum

You do not need to fully memorize the electromagnetic spectrum but it may be helpful to know that visible red light is about 700nm and visible violet light is about 400nm because that was covered in lecture.
by Diana Bibireata 1B
Thu Oct 25, 2018 9:33 pm
Forum: Quantum Numbers and The H-Atom
Topic: Nodal Planes and test 2
Replies: 3
Views: 94

Re: Nodal Planes and test 2

Yes, know that the s orbital has no nodal planes, the p orbital has 1 nodal plane, and the d orbital has 2.
by Diana Bibireata 1B
Thu Oct 25, 2018 9:30 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Degeneracy
Replies: 6
Views: 139

Re: Degeneracy

The textbook says that if something is degenerate it has the same energy. For example, atomic orbitals that are in the same sub shell.
by Diana Bibireata 1B
Thu Oct 18, 2018 10:19 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Nodal Planes [ENDORSED]
Replies: 4
Views: 139

Re: Nodal Planes [ENDORSED]

Essentially in a nodal plane no electrons will be found. You should know how many nodal planes there are for each orbital (no nodal planes in s orbital, 1 in p orbital, simplest d orbital has 2, etc.)
by Diana Bibireata 1B
Thu Oct 18, 2018 9:55 pm
Forum: Photoelectric Effect
Topic: 1B.7
Replies: 3
Views: 78

Re: 1B.7

For part a you use the equation
(because c and h are constants and the problem gives you the wavelength). This gives you the energy of a sodium atom. Then, for part b, after you find the number of atoms of sodium, you simply multiply it by the energy of one sodium atom.
by Diana Bibireata 1B
Thu Oct 18, 2018 9:44 pm
Forum: DeBroglie Equation
Topic: De Broglie
Replies: 12
Views: 428

Re: De Broglie

The DeBroglie equation only applies to particles with resting mass (for example electrons) that has momentum (p). You can't use this equation for something like light because light has no mass when at rest.
by Diana Bibireata 1B
Thu Oct 11, 2018 10:07 pm
Forum: Properties of Light
Topic: Problem 1A.9 (7th edition)
Replies: 5
Views: 53

Re: Problem 1A.9 (7th edition)

In the equation c= you do use meters (because the unit for c is meters per second)
But it is important to note that wavelengths in the visible spectrum are usually given in nanometers (which is 10-9m) so just also know this conversion.
by Diana Bibireata 1B
Thu Oct 11, 2018 10:00 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Equation
Replies: 3
Views: 90

Re: Photoelectric Effect Equation

Essentially each photon needs to have more energy than than the energy to remove an electron from the metal (aka the threshold energy). So if 1000 photons hit the metal surface and each individual photon has enough energy, then 1000 electrons will be released.
by Diana Bibireata 1B
Thu Oct 11, 2018 9:48 pm
Forum: Properties of Light
Topic: Calculate values of n
Replies: 2
Views: 47

Re: Calculate values of n

In this problem they give you the wavelength so you use the equation \nu =c/\lambda to find the frequency. Then you want to use the Rydberg equation which is \nu =R(1/n_{1}^{2}-1/n_{2}^{2}) . Your n 1 value will be 1 because it is in the uv spectrum so it is a part of the Lyman series. From ...
by Diana Bibireata 1B
Sat Oct 06, 2018 12:17 pm
Forum: Empirical & Molecular Formulas
Topic: HW F11
Replies: 4
Views: 131

Re: HW F11

NH4+ (ammonium) and H2PO4- (dihydrogen phosphate) are polyatomic ions which is why they wrote it like that.
by Diana Bibireata 1B
Thu Oct 04, 2018 5:51 pm
Forum: Balancing Chemical Reactions
Topic: 7th Edition L.35 question
Replies: 3
Views: 105

Re: 7th Edition L.35 question

I noticed that too and I believe the answer key is correct and the reactant should be Fe3Br8. This would make sense because the product from the second reaction should be one of the reactants in the 3rd reaction.
by Diana Bibireata 1B
Thu Oct 04, 2018 2:21 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Polyatomic ions
Replies: 3
Views: 68

Re: Polyatomic ions

In the end you will have to memorize them but there are a few ways that will make memorizing them easier. 1. polyatomic ions ending with -ate have one more oxygen atom than those ending with -ite. (ex. nitrate: NO 3 - and nitrite: NO 2 - ) 2. ions with per- have one more oxygen atom then those endin...

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