Search found 65 matches

by Emily Ng_4C
Tue Mar 12, 2019 5:00 pm
Forum: Van't Hoff Equation
Topic: Test #2
Replies: 5
Views: 301

Test #2

the ionic dissociation of water is given by the following reaction: the deltaH for the reaction is 58 kJ/mol. The Kw for the reaction at 25 degree Celsius is 10 ^-14. Is the pH of 7 acidic or basic at 10 degree Celsius?
2H20 --> H3O+ + OH-

Why is the answer acidic?
by Emily Ng_4C
Tue Mar 12, 2019 4:48 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate dependency on [H2O]
Replies: 1
Views: 44

Re: Rate dependency on [H2O]

This is rare because H2O usually exists as the solvent and the concentration is too large to show any significant change.
by Emily Ng_4C
Tue Mar 12, 2019 4:42 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: order of a cell diagram
Replies: 4
Views: 107

Re: order of a cell diagram

the electrode goes on the outside while the anode is to the left and the cathode is to the right of the double lines (||), indicating a salt bridge. Species that are in the same phase are separated by a comma, while everything else is separated by a single line (|). I'm not sure what you mean by h+.
by Emily Ng_4C
Fri Mar 08, 2019 2:34 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Rate Order Graphs
Replies: 3
Views: 84

Rate Order Graphs

What is the logic behind choosing the model with the most linear graph as the rate order?
by Emily Ng_4C
Fri Mar 08, 2019 2:32 pm
Forum: Zero Order Reactions
Topic: Determining Rate Orders
Replies: 3
Views: 58

Determining Rate Orders

How can you tell what the order of each reactant is based on a table of rates and concentrations? Is there a formula or pattern?
by Emily Ng_4C
Tue Mar 05, 2019 12:58 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Units
Replies: 4
Views: 88

Re: Units

Zero-order should be M/s. First-order should be s^-1. and second-order should be M^-1 * s^-1.
by Emily Ng_4C
Tue Feb 26, 2019 3:24 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Problem 6L.3
Replies: 1
Views: 45

Re: Problem 6L.3

It is written that way because on the ride side of the double lines, which indicate a salt bridge, represents the cathode where reduction happens. The Cl2 is being reduced and gaining two electrons.
by Emily Ng_4C
Tue Feb 26, 2019 3:19 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: # 14.9 b 6th ed
Replies: 1
Views: 38

Re: # 14.9 b 6th ed

When you balance the half reactions and multiply the equations with a constant to get the same moles of electrons exchanged, it should be 6.
by Emily Ng_4C
Tue Feb 26, 2019 3:17 pm
Forum: Balancing Redox Reactions
Topic: Balancing Rules for Redox Reactions
Replies: 3
Views: 63

Re: Balancing Rules for Redox Reactions

Make sure the number of atoms and the charges are equal on both sides.
by Emily Ng_4C
Fri Feb 22, 2019 12:34 pm
Forum: Van't Hoff Equation
Topic: Van't Hoff Equation
Replies: 3
Views: 238

Van't Hoff Equation

What is the purpose and concept behind the Van't Hoff Equation?
by Emily Ng_4C
Fri Feb 22, 2019 12:30 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic Cells
Replies: 2
Views: 46

Galvanic Cells

Why do electrons flow from the anode to the cathode?
by Emily Ng_4C
Fri Feb 22, 2019 12:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 5
Views: 83

Salt Bridge

What is the purpose of the salt bridge?
by Emily Ng_4C
Thu Feb 14, 2019 12:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: buffer
Replies: 2
Views: 77

Re: buffer

A buffer is something that limits the change in pH in an acid-base reaction.
by Emily Ng_4C
Thu Feb 14, 2019 12:33 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Molar and specific heat capacity
Replies: 3
Views: 97

Re: Molar and specific heat capacity

Specific heat capacity is for mass while molar heat capacity is for moles.
by Emily Ng_4C
Thu Feb 14, 2019 12:32 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: 6th edition 9.11
Replies: 1
Views: 215

Re: 6th edition 9.11

When you divide the pressures, the atm's cancel each other out. Your ending units should be J/ K.
by Emily Ng_4C
Tue Feb 05, 2019 1:17 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: ΔH and ΔU
Replies: 6
Views: 142

Re: ΔH and ΔU

Since delta H and delta U values can differ depending on the conditions the reaction is happening in, the degree symbol tells us that the reaction is happening under a standard condition of 1atm.
by Emily Ng_4C
Tue Feb 05, 2019 1:07 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Enthropy
Replies: 2
Views: 128

Re: Enthropy

Entropy values are usually given to us in a table.
by Emily Ng_4C
Tue Feb 05, 2019 1:01 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Microstate
Replies: 7
Views: 187

Microstate

What is a microstate and how does it relate to entropy?
by Emily Ng_4C
Tue Jan 29, 2019 3:14 pm
Forum: Phase Changes & Related Calculations
Topic: temperature
Replies: 3
Views: 63

Re: temperature

The temperature doesn't change because a phase change is happening. The heat being put into the system is causing the phase change and causing the molecules to overcome all the attractive forces, which allows a substance to go from solid to liquid and a liquid to a gas.
by Emily Ng_4C
Tue Jan 29, 2019 3:12 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Method #3
Replies: 2
Views: 77

Re: Method #3

Method #3 is focused on the heat capacity, which is the heat required to raise the temp of an object by 1 degree C. The change in heat or enthalpy can be solved by this equation: qp = enthalpy = nCpdeltaT (The p's are subscripts). Cp represents the molar heat capacity at constant pressure. DeltaT is...
by Emily Ng_4C
Tue Jan 29, 2019 3:06 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: enthalpy
Replies: 4
Views: 72

Re: enthalpy

A state function means that we only care what happens at the beginning and at the end and it isn't dependent on the path taken. So, enthalpy is a state function because we can add and subtract heat to get the change in enthalpy.
by Emily Ng_4C
Tue Jan 22, 2019 3:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th Edition 6E.3
Replies: 1
Views: 45

Re: 7th Edition 6E.3

Ka2 represents the second reaction that polyprotic compounds often go through. In this case, H2SO4's second reaction (HSO4- +H20 --> SO42- +H3O+) produces an insignificant amount of H3O+ that we ignore the second ionization.
by Emily Ng_4C
Tue Jan 22, 2019 3:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka and Kb
Replies: 2
Views: 52

Re: Ka and Kb

Ka and Kb values should be given to us
by Emily Ng_4C
Tue Jan 22, 2019 3:04 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Hmwrk 11.77 6th edition
Replies: 2
Views: 61

Re: Hmwrk 11.77 6th edition

For part b, the bond holding X2 together is broken to form 2X. Breaking bonds is an endothermic reaction that requires the absorbance of heat/energy.
by Emily Ng_4C
Tue Jan 22, 2019 3:02 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka and Kb
Replies: 3
Views: 57

Re: Ka and Kb

If the Ka or Kb is greater than 10^3, then it is a strong acid or base. If the Ka or Kb is less than 10^-3, then it is a weak acid or weak base
by Emily Ng_4C
Wed Jan 16, 2019 5:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Taking x away in a Ka calculation
Replies: 5
Views: 100

Re: Taking x away in a Ka calculation

Sometimes, the x is so small that it doesn't have an effect on the overall concentration. For instance, let's say the initial concentration is 1 x 10^-1 and the K value is extremely small, we would know that the numerator/reactants would also have to be extremely small so that the ratio will equal t...
by Emily Ng_4C
Wed Jan 16, 2019 5:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solids and liquids in K
Replies: 6
Views: 149

Re: Solids and liquids in K

Solids aren't included because they don't have a concentration. Liquids aren't included because they are usually solvents and don't change much in concentration throughout the reaction. Liquids would just show up on both sides of the equation and cancel each other out.
by Emily Ng_4C
Wed Jan 16, 2019 5:04 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Percentage Ionization
Replies: 4
Views: 86

Re: Percentage Ionization

Miya Lopez 1I wrote:Also, what does it mean to be "completely ionized"?
In class Dr. Lavelle stated that "Ba(OH)2 (aq) is a strong base, essentially completely ionized."


To completely ionized means to completely dissociate. For instance, BaOHsub2 will dissociate completely into Ba2+ and OH-
by Emily Ng_4C
Wed Jan 16, 2019 5:03 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Percentage Ionization
Replies: 4
Views: 86

Re: Percentage Ionization

Percent ionization shows how much something dissociated. It can be calculated by taking the concentration of its ions divided by the original compound and multiplied by 100. For instance, weak acids will have a varying percent ionization because only a small percent of it will dissociate. Percent io...
by Emily Ng_4C
Tue Jan 08, 2019 5:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K vs. Q
Replies: 2
Views: 50

Re: K vs. Q

Q shows whether the reaction will move more to the right or to the left, producing either more products or reactants. For instance, if Q<K, then the reaction will shift toward the right. This will produce more products and eventually, Q will equal K.
by Emily Ng_4C
Tue Jan 08, 2019 5:22 pm
Forum: Ideal Gases
Topic: R in PV=nRT
Replies: 11
Views: 259

Re: R in PV=nRT

R is the gas constant and it is important to note that it differs depending on whether atm, torr, or bar is used for the pressure unit.
by Emily Ng_4C
Tue Jan 08, 2019 5:20 pm
Forum: Ideal Gases
Topic: Solid/Liquid in Reactions
Replies: 4
Views: 75

Re: Solid/Liquid in Reactions

Solids are not included because they don't have a concentration because solids are usually pure. Liquids are not included because they usually exist as a solvent and thus has such a large concentration that it barely changes throughout the reaction.
by Emily Ng_4C
Mon Dec 03, 2018 9:26 am
Forum: Hybridization
Topic: s character
Replies: 3
Views: 76

Re: s character

S-character is the ratio of the S to the P. For instance, an sp hybrid orbital would have a 1:1 and sp2 would be 1:2. And so, sp would have more s-character than sp2.
by Emily Ng_4C
Mon Dec 03, 2018 9:21 am
Forum: Naming
Topic: Latin Names
Replies: 5
Views: 119

Latin Names

What are all the elements that have latin names do we need to know?
by Emily Ng_4C
Mon Dec 03, 2018 9:20 am
Forum: Naming
Topic: Anions
Replies: 3
Views: 78

Anions

Do we end all names of anions with an -ate even if the overall charge or the anion is not negative?
by Emily Ng_4C
Fri Nov 30, 2018 2:00 pm
Forum: Sigma & Pi Bonds
Topic: Sigma bonds
Replies: 6
Views: 202

Re: Sigma bonds

Sigma bonds are when two orbitals bond at one point, while pi bonds are when two orbitals bond at two points.
by Emily Ng_4C
Fri Nov 30, 2018 1:56 pm
Forum: Lewis Structures
Topic: Lewis Structures for Molecules with H- AND O- atoms
Replies: 3
Views: 63

Re: Lewis Structures for Molecules with H- AND O- atoms

When you see an OH in a molecular formula, the H usually goes on the O. However, to be sure, calculate the formal charges and make sure it aligns with how you are drawing the molecules.
by Emily Ng_4C
Fri Nov 30, 2018 1:50 pm
Forum: Ionic & Covalent Bonds
Topic: Polar and Nonpolar
Replies: 3
Views: 84

Re: Polar and Nonpolar

A molecule is polar when the electron distribution is not equal and the dipole moments do not cancel out. However, when thinking about whether a molecule is polar or not, it is important to think of it in 3-D. For instance, CCl4 is tetrahedral and nonpolar.
by Emily Ng_4C
Fri Nov 30, 2018 1:47 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: H-Bonding and Dipole Dipole
Replies: 2
Views: 98

Re: H-Bonding and Dipole Dipole

Hydrogen Bonding is a specific dipole-dipole bonding. H-Bonding only occurs between Hydrogen and Fluorine, Oxygen, or Nitrogen.
by Emily Ng_4C
Fri Nov 23, 2018 12:04 pm
Forum: Hybridization
Topic: d-block
Replies: 3
Views: 83

Re: d-block

The energy will be between the orbitals because it is an average of the orbitals that are hybridizing.
by Emily Ng_4C
Fri Nov 23, 2018 12:03 pm
Forum: Hybridization
Topic: reason for hybridization
Replies: 9
Views: 310

Re: reason for hybridization

Hybridization occurs molecules/atoms can bond with other molecules/atoms. To my understanding, looking at the electronic configuration, electrons aren't always in the spot to bond. For instance, carbon's electronic configuration is 1s22s22p2. It only has 2 unpaired electrons even though we know that...
by Emily Ng_4C
Fri Nov 23, 2018 11:59 am
Forum: Dipole Moments
Topic: Bond Angles
Replies: 8
Views: 193

Re: Bond Angles

I would suggest memorizing the basic angles like tetrahedral is 109.5, trigonal planar is 120, and linear is 180. Then, you should understand how lone pairs affect those angles. Lone pairs push the bonded atoms together making the angles smaller. For instance, a trigonal pyramidal is <109.5.
by Emily Ng_4C
Fri Nov 16, 2018 12:30 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizability
Replies: 3
Views: 138

Re: Polarizability

Polarizability is how much the electrons in an atom can be distorted. For example, atoms with more electrons tend to be more polarizable.
by Emily Ng_4C
Fri Nov 16, 2018 12:22 pm
Forum: Sigma & Pi Bonds
Topic: Sigma and Pi bonds
Replies: 4
Views: 108

Re: Sigma and Pi bonds

What are the purposes of sigma and pi bonds? Do they just create a bigger area for electron movement? I believe sigma and pi bonds give you a more specific visual representation of how two atoms/molecules bond. For instance, sigma bond is where they bond at one point, and a pi bond is where they bo...
by Emily Ng_4C
Fri Nov 16, 2018 12:19 pm
Forum: Sigma & Pi Bonds
Topic: Significance of sigma and pi bonds
Replies: 2
Views: 89

Re: Significance of sigma and pi bonds

Sigma and Pi bond tell you more specifically how two atoms/molecules bond. For instance, a sigma bond is where two atoms/molecules bond at one point, while a pi bond is where two atoms/molecules bond at two points.
by Emily Ng_4C
Fri Nov 09, 2018 9:44 am
Forum: Dipole Moments
Topic: HCl
Replies: 6
Views: 120

Re: HCl

HCl has a permanent dipole because Cl is one of the most electronegative element while H isn't. So, Cl has the tendency to pull all the electron, creating a dipole.
by Emily Ng_4C
Fri Nov 09, 2018 9:41 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Disperson forces
Replies: 4
Views: 106

Re: Disperson forces

The more electrons a molecule has, the more polarizable it is. Because there are more dispersion forces happening in larger molecules because of the number of electrons, the interactions are likely to be a liquid substance over a gaseous substance. This is evident in why F2 is a gas and Br2 is a liq...
by Emily Ng_4C
Fri Nov 09, 2018 9:36 am
Forum: Dipole Moments
Topic: Van der Waals forces
Replies: 2
Views: 92

Re: Van der Waals forces

Molecules can be neutral/nonpolar because all the electrons are orienting themselves around the central atom evenly. However, since they still have electrons, the electrons move around, creating a temporary dipole moment that interacts with other molecules with a temporary dipole moment.
by Emily Ng_4C
Fri Nov 02, 2018 1:49 pm
Forum: Ionic & Covalent Bonds
Topic: Ionization Energy
Replies: 2
Views: 55

Re: Ionization Energy

The ionization energy increases because there is a stronger positive nuclear charge that pulls the electron towards the center. In addition, as there are more electrons in one cloud, the more it wants to fill up the octet rather than getting rid of the electrons.
by Emily Ng_4C
Fri Nov 02, 2018 1:43 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge of Ions
Replies: 9
Views: 241

Re: Formal Charge of Ions

You want each individual atom to be as close to zero as possible, but the overall formal charges should add up to the charge of the molecule.
by Emily Ng_4C
Fri Nov 02, 2018 1:37 pm
Forum: Ionic & Covalent Bonds
Topic: electronegativity troughout a covalent bond
Replies: 3
Views: 125

Re: electronegativity troughout a covalent bond

Yes, the more negative atom will be the more electronegative atom since they want to attract electrons to fill their outer shell.
by Emily Ng_4C
Fri Oct 26, 2018 8:04 pm
Forum: Ionic & Covalent Bonds
Topic: Bonding Between Cations and Anions
Replies: 3
Views: 53

Re: Bonding Between Cations and Anions

(NH4)2+ and (SO4)2- are cations and anions which form an ionic bond through the transferring of electrons.
by Emily Ng_4C
Fri Oct 26, 2018 8:02 pm
Forum: Ionic & Covalent Bonds
Topic: Valence Electrons
Replies: 4
Views: 105

Re: Valence Electrons

You base it off of the group the elements are in. For example, Group 1 would have 1 valence electron. However, the transition metals will vary in how many valence electrons they will have.
by Emily Ng_4C
Fri Oct 26, 2018 8:00 pm
Forum: Ionic & Covalent Bonds
Topic: Chemical Bonding and Periodic Trends
Replies: 4
Views: 107

Re: Chemical Bonding and Periodic Trends

Yes. For example, if an element has a high ionization energy, it is less likely to have an electron removed. Rather, it would accept electrons to meet the octet rule. Vice versa as well.
by Emily Ng_4C
Fri Oct 26, 2018 7:57 pm
Forum: Properties of Light
Topic: Speed of Light
Replies: 12
Views: 277

Re: Speed of Light

No, I don't think anything is faster than the speed of light.
by Emily Ng_4C
Tue Oct 16, 2018 10:19 am
Forum: Photoelectric Effect
Topic: Spectroscopic series
Replies: 2
Views: 109

Re: Spectroscopic series

I think the lyman and balmer series are the only ones we need to know. Lyman series is when an electron drops back down to n=1 while Balmer is when an electron drops back down to n=2.
by Emily Ng_4C
Tue Oct 16, 2018 10:12 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Formula
Replies: 3
Views: 92

Formula

Why is there a negative in E=-hR/n^2?
by Emily Ng_4C
Tue Oct 16, 2018 10:11 am
Forum: Properties of Light
Topic: Vocab
Replies: 5
Views: 124

Vocab

What does it mean for something to be quantized?
by Emily Ng_4C
Fri Oct 12, 2018 12:52 am
Forum: Photoelectric Effect
Topic: Threshold energy
Replies: 5
Views: 295

Re: Threshold energy

Threshold energy is the minimum amount of energy needed to eject an electron
by Emily Ng_4C
Fri Oct 12, 2018 12:48 am
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical Equations [ENDORSED]
Replies: 4
Views: 169

Re: Balancing Chemical Equations [ENDORSED]

For combustion reactions, a hydrocarbon is usually reacted with oxygen to form water and carbon dioxide. To arrange reactants and products, you need to know what is actually going on in the reaction and what type of reaction it is.
by Emily Ng_4C
Fri Oct 12, 2018 12:46 am
Forum: Molarity, Solutions, Dilutions
Topic: memorizing [ENDORSED]
Replies: 4
Views: 383

Re: memorizing [ENDORSED]

Writing out the units usually helps with understanding what the next step is. For example, molar mass is g/mol and to find the number of mols for a certain mass. You would take the mass and divide it by the molar mass. This would cancel out the grams.
by Emily Ng_4C
Wed Oct 03, 2018 6:34 pm
Forum: Limiting Reactant Calculations
Topic: Finding theoretical yield
Replies: 6
Views: 161

Re: Finding theoretical yield

The amount of product the limiting reactant produces will be the actual yield because you can't produce more if there is not enough of one of the parts.
by Emily Ng_4C
Wed Oct 03, 2018 6:32 pm
Forum: Limiting Reactant Calculations
Topic: Limiting reactants product of moles
Replies: 4
Views: 110

Re: Limiting reactants product of moles

You can convert the mass of CaCO3 to moles and then use the mole to mole ration from the chemical equation to find the moles of CO2.
by Emily Ng_4C
Wed Oct 03, 2018 6:27 pm
Forum: Balancing Chemical Reactions
Topic: Combustion
Replies: 6
Views: 181

Re: Combustion

Combustion requires the presence of O2 and will always form H2O and CO2.

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