Search found 79 matches
- Sun Feb 09, 2020 7:48 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Expansion work/ Compression
- Replies: 7
- Views: 354
Re: Expansion work/ Compression
During expansion, work is being done so you need a negative sign while compression you need a positive sign.
- Sun Feb 09, 2020 7:47 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Negative Heat Capacity
- Replies: 4
- Views: 278
Re: Negative Heat Capacity
No, because you can't have a negative value for the amount of energy required to raise the temperature.
- Sun Feb 09, 2020 7:46 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Calorimeter
- Replies: 5
- Views: 372
Re: Calorimeter
A calorimeter measure the heat change when a reaction occurs. A bomb calorimeter, though, has constant volume.
- Sun Feb 09, 2020 7:31 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Calorimeters
- Replies: 17
- Views: 940
Re: Calorimeters
A bomb calorimeter is constant volume.
- Sun Feb 09, 2020 7:30 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Calorimeter and Bomb Calorimeter
- Replies: 4
- Views: 414
Re: Calorimeter and Bomb Calorimeter
A calorimeter measures the change in temperature, but a bomb calorimeter has constant volume.
- Sun Feb 09, 2020 7:21 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Closed Systems
- Replies: 13
- Views: 650
Re: Closed Systems
Energy cannot leave in a closed system, so only temperature or pressure can change.
- Sun Feb 09, 2020 7:14 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Cp/Cv
- Replies: 7
- Views: 359
Re: Cp/Cv
Unless stated, just assume that it is at constant pressure.
- Sun Feb 02, 2020 10:03 am
- Forum: Phase Changes & Related Calculations
- Topic: Enthalpy vs Change in Internal Energy
- Replies: 4
- Views: 280
Re: Enthalpy vs Change in Internal Energy
Enthalpy is the heat absorbed/released while internal energy is just the total amount of energy.
- Sun Feb 02, 2020 10:02 am
- Forum: Phase Changes & Related Calculations
- Topic: Calorimeter
- Replies: 8
- Views: 537
Re: Calorimeter
A bomb calorimeter is more resistant to pressure.
- Sat Feb 01, 2020 10:29 pm
- Forum: Phase Changes & Related Calculations
- Topic: DELTA H Vs Q
- Replies: 7
- Views: 362
Re: DELTA H Vs Q
Delta H is based on the amount of substance used while Q is the amount of energy released in total.
- Sat Feb 01, 2020 10:28 pm
- Forum: Phase Changes & Related Calculations
- Topic: Open vs Isolated System
- Replies: 15
- Views: 1254
Re: Open vs Isolated System
In a closed system, energy cannot be transferred to the outside.
- Sat Feb 01, 2020 10:27 pm
- Forum: Phase Changes & Related Calculations
- Topic: Why does steam cause burns?
- Replies: 29
- Views: 1114
Re: Why does steam cause burns?
Steam has more energy than liquid because more energy is required to transform a liquid into steam. For this reason, as steam touches the skin, much more energy is transferred, causing burns.
- Sun Jan 26, 2020 10:12 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Ka and Kb
- Replies: 10
- Views: 482
Re: Ka and Kb
Yes, although I believe strong acids and bases have K values, they are so excessively big.
- Sun Jan 26, 2020 10:11 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: endothermic
- Replies: 8
- Views: 295
Re: endothermic
If a reaction is endothermic, heat is required so adding heat to is would favor the reactants.
- Sun Jan 26, 2020 10:10 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: exothermic reactions
- Replies: 19
- Views: 1895
Re: exothermic reactions
In an exothermic reaction, heat is produced, so there is heat in the products. Adding heat to the reaction would favor the reactants.
- Sun Jan 26, 2020 10:07 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Gas Constant
- Replies: 13
- Views: 518
Re: Gas Constant
There's a few different gas constants for different units but they are the same constant, just with different units. They are all on the formula sheet.
- Sun Jan 26, 2020 10:04 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Clarification on example
- Replies: 2
- Views: 159
Re: Clarification on example
pH is equal to the -log[H3o+] so the lower the concentration of [H3O], the smaller the pH, meaning it is a strong acid. Since the pH of H2O is 7, neutral, [H3O]=107.
- Sun Jan 26, 2020 9:59 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Weak acid/base
- Replies: 14
- Views: 624
Re: Weak acid/base
If the acid or base isn't dissociated completely, it is weak. Otherwise, a very low or a very high pH (or a very high or a very low pOH) means it is a strong acid or base.
- Sun Jan 26, 2020 9:52 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: removing H2 from N2 + 3H2 -> 2NH3
- Replies: 7
- Views: 1943
Re: removing H2 from N2 + 3H2 -> 2NH3
Removing H2 would make the reaction shift toward the reactants because of Le Chatlier's, so more N2 would be produced.
- Sun Jan 26, 2020 9:51 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Finding Ka from pH
- Replies: 5
- Views: 287
Re: Finding Ka from pH
[H30+]=-logpH and [OH-]=-logpOH.
- Tue Jan 21, 2020 1:35 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Kc vs K
- Replies: 7
- Views: 313
Re: Kc vs K
Kc is the equilibrium constant that's calculated by the concentrations but it is calculated the same way as just "K."
- Tue Jan 21, 2020 1:22 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: X was ignored
- Replies: 27
- Views: 992
Re: X was ignored
Since Ka is smaller than 103 you can ignore the x in the denominator. Since K is so small, x is negligible in this case and can be ignored for the sake of convenience of calculating.
- Tue Jan 21, 2020 1:18 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: pKa and pKb
- Replies: 17
- Views: 840
Re: pKa and pKb
p just means its the log of something. so pKa is log(Ka) and pKb is log(Kb).
- Tue Jan 21, 2020 1:10 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: temperature
- Replies: 10
- Views: 409
Re: temperature
Temperature affects the equilibrium constant so if the reaction is exothermic (heat in the products) added heat will shift the reaction left and removing heat will shift the reaction right. On the other hand, if the reaction is endothermic (heat in reactants) added heat will shift the reaction right...
- Tue Jan 21, 2020 1:08 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Sig Figs for pH/pOH
- Replies: 7
- Views: 330
Re: Sig Figs for pH/pOH
The number of sig figs to the answer of a log is the amount of sig figs after the decimal of the number you took the log of.
- Tue Jan 21, 2020 1:07 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: H20 in the ICE table
- Replies: 26
- Views: 1400
Re: H20 in the ICE table
You include any gases, but since solids and liquids have negligible change they are not included in ice box or the equilibrium constant.
- Tue Jan 21, 2020 12:59 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Directionality of Acid/Base Equations
- Replies: 4
- Views: 113
Re: Directionality of Acid/Base Equations
Weak acids and bases are reversible because they don't dissociate completely, but strong acids and bases on the other hand dissociate completely so they are not reversible.
- Tue Jan 21, 2020 12:58 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: lewis structure
- Replies: 11
- Views: 407
Re: lewis structure
No he only draws the structures for clarity but they are only for 14a not 14b.
- Sun Jan 12, 2020 11:17 pm
- Forum: Ideal Gases
- Topic: Kc and Kp
- Replies: 8
- Views: 235
Re: Kc and Kp
Kc is solved using concentration while Kp is solved using partial pressures.
- Sun Jan 12, 2020 11:16 pm
- Forum: Ideal Gases
- Topic: Understanding Q
- Replies: 19
- Views: 679
Re: Understanding Q
Q is solved the same way as K, Q is just not at equilibrium.
- Sun Jan 12, 2020 11:15 pm
- Forum: Ideal Gases
- Topic: PV = nRT
- Replies: 16
- Views: 1818
Re: PV = nRT
P=pressure
V=volume
N=moles
R= ideal gas constant
T=temperature
V=volume
N=moles
R= ideal gas constant
T=temperature
- Sun Jan 12, 2020 11:14 pm
- Forum: Ideal Gases
- Topic: Q vs. K
- Replies: 10
- Views: 293
Re: Q vs. K
K is the constant at equilibrium while Q is the constant at any point in the reaction.
- Sun Jan 12, 2020 11:13 pm
- Forum: Ideal Gases
- Topic: Vapor Pressure
- Replies: 4
- Views: 159
Re: Vapor Pressure
When the gas and liquid states are at equilibrium, the pressure of the gas is known as the vapor pressure.
- Tue Jan 07, 2020 11:18 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5G.3
- Replies: 8
- Views: 500
Re: 5G.3
Partial pressure is used in this case because they are gases.
- Tue Jan 07, 2020 11:15 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Heterogenous vs. Homogenous equations
- Replies: 6
- Views: 263
Re: Heterogenous vs. Homogenous equations
Homogeneous equations are all in the same state of matter, while heterogeneous are in mixed states of matter.
- Tue Jan 07, 2020 11:14 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Very Large K
- Replies: 12
- Views: 2527
Re: Very Large K
Seeing as the formula for K is K = [P]/[R], the larger the concentration of products and the smaller the concentration of reactants there are, the larger K will be.
- Mon Jan 06, 2020 5:54 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Calculating Kc
- Replies: 4
- Views: 120
Re: Calculating Kc
Solids and liquids have constant concentrations so they don't change, so there is no need to calculate them.
- Mon Jan 06, 2020 5:50 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium Constant
- Replies: 3
- Views: 101
Re: Equilibrium Constant
According to the constant formula (K = [P]/[R]) the value of K will be higher, meaning there is more product than reactant left at the end. This being said, a more stable molecule results in more product and less reverse reaction happening.
Re: Chelating
A ligand is a chelate when it bonds in more than one area.
- Sun Dec 01, 2019 11:24 pm
- Forum: Naming
- Topic: -bis, -tris, etc
- Replies: 5
- Views: 424
Re: -bis, -tris, etc
You use these suffixes when there is already a suffix in the name.
- Sun Dec 01, 2019 11:24 pm
- Forum: Naming
- Topic: How to Know the Charge of Ions
- Replies: 7
- Views: 469
Re: How to Know the Charge of Ions
You will have to memorize the polyatomic ions, but I'm pretty sure he won't give anything that's too difficult.
- Sun Dec 01, 2019 11:23 pm
- Forum: Naming
- Topic: When to change to -ate?
- Replies: 3
- Views: 291
Re: When to change to -ate?
If the charge is negative you add -ate.
- Sun Dec 01, 2019 11:21 pm
- Forum: Naming
- Topic: Brackets in Chem. Formula
- Replies: 5
- Views: 323
Re: Brackets in Chem. Formula
The transition metal and its ligands go inside the bracket. Everything else is outside.
- Sun Nov 24, 2019 11:11 pm
- Forum: Resonance Structures
- Topic: Resonance Structures
- Replies: 18
- Views: 1049
Re: Resonance Structures
They are structure with the same formal charges.
- Sun Nov 24, 2019 11:09 pm
- Forum: Resonance Structures
- Topic: Bond length
- Replies: 5
- Views: 423
Re: Bond length
Yes they are all the same.
- Sun Nov 24, 2019 11:09 pm
- Forum: Resonance Structures
- Topic: Resonance and Naming
- Replies: 11
- Views: 839
Re: Resonance and Naming
No, because it is the same structure it has the same name.
- Sun Nov 24, 2019 11:08 pm
- Forum: Resonance Structures
- Topic: Resonance structures
- Replies: 15
- Views: 754
Re: Resonance structures
Resonance structures are different ways a lewis structure can be drawn, but they have the same formal charge.
- Sun Nov 24, 2019 11:05 pm
- Forum: Resonance Structures
- Topic: Lone Pairs
- Replies: 3
- Views: 330
Re: Lone Pairs
Lone pairs position themselves in a way where there is minimal repulsion.
- Sat Nov 16, 2019 10:02 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polar vs. Nonpolar
- Replies: 12
- Views: 742
Re: Polar vs. Nonpolar
You need to draw the lewis structure and it helps to draw arrows to the negative charged atom from the positively charged ion. If there are two different poles, then the molecule is polar, if both cancel out, it is nonpolar.
- Sat Nov 16, 2019 10:00 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 2E 11 b)
- Replies: 4
- Views: 187
Re: 2E 11 b)
Chlorine cannot have more than a single bond so we know that there are 3 single bonds on iodine, meaning there will be two left over lone pairs on iodine.
- Sat Nov 16, 2019 9:59 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: polar or non polar?
- Replies: 7
- Views: 499
Re: polar or non polar?
You need both to figure out if it is polar/nonpolar. Electronegativity will tell where the pull of electrons is, but the Lewis structure shows the positioning of the atoms and whether they will cancel or not.
- Sun Nov 10, 2019 9:03 pm
- Forum: Electronegativity
- Topic: Karen's worksheet #12
- Replies: 3
- Views: 188
Re: Karen's worksheet #12
There is a greater difference in electronegativity.
- Sun Nov 10, 2019 8:58 pm
- Forum: Electronegativity
- Topic: ionic character
- Replies: 9
- Views: 623
Re: ionic character
Ionic character, I believe, is a covalently bond that has such strong ionic character (electronegativity) that a covalently bonded substance is almost ionic.
- Sun Nov 10, 2019 8:57 pm
- Forum: Electronegativity
- Topic: Ionic or covalent?
- Replies: 17
- Views: 745
Re: Ionic or covalent?
An ionic bond is typically comprised of a non metal and a metal while a covalent bond is usually two non metals.
- Sun Nov 10, 2019 8:56 pm
- Forum: Electronegativity
- Topic: memorizing tables
- Replies: 9
- Views: 303
Re: memorizing tables
Just know the general trend on the periodic table.
- Sun Nov 10, 2019 8:56 pm
- Forum: Electronegativity
- Topic: Ionization Energy vs. Electronegativity
- Replies: 9
- Views: 9584
Re: Ionization Energy vs. Electronegativity
Both ionization energy and electronegativity increase toward the upper right hand side of the periodic table.
- Sun Nov 10, 2019 8:54 pm
- Forum: Electronegativity
- Topic: Electron Affinity and Electronegativity
- Replies: 7
- Views: 397
Re: Electron Affinity and Electronegativity
Electron affinity is the energy released when an electron in added to to an atom, while electronegativity is how much an atom pulls electrons.
- Sun Nov 10, 2019 8:49 pm
- Forum: Octet Exceptions
- Topic: Incomplete octets
- Replies: 3
- Views: 294
Re: Incomplete octets
Hydrogen, helium, and boron are all exceptions to the rule.
- Wed Oct 30, 2019 9:04 pm
- Forum: Lewis Structures
- Topic: Lone Pairs
- Replies: 10
- Views: 404
Re: Lone Pairs
Lone pair electrons are electrons that are not bonded to other elements. In other words, they are not shared with any other elements.
- Wed Oct 30, 2019 9:03 pm
- Forum: Lewis Structures
- Topic: Exceptions to the Octet Rule
- Replies: 3
- Views: 117
Re: Exceptions to the Octet Rule
Elements P, Cl, and S do not adhere to the octet rule because of the d orbital.
- Wed Oct 30, 2019 9:01 pm
- Forum: Lewis Structures
- Topic: Creating Lewis Structures
- Replies: 7
- Views: 277
Re: Creating Lewis Structures
Typically, the element with the lowest ionization energy will go in the center.
- Wed Oct 30, 2019 8:59 pm
- Forum: Lewis Structures
- Topic: Valence electrons
- Replies: 5
- Views: 219
Re: Valence electrons
Sulfur, Phosphorous, and Chlorine all deviate from the octet rule because they have the extra d orbitals.
- Wed Oct 30, 2019 8:58 pm
- Forum: Lewis Structures
- Topic: Drawing lewis structures
- Replies: 8
- Views: 222
Re: Drawing lewis structures
If the question asks for Lewis structures, I assume it is just the 2D model without angles. I'm sure if we learn about bond angles there will be a separate question.
- Sun Oct 20, 2019 11:48 pm
- Forum: Properties of Light
- Topic: Speed of light
- Replies: 13
- Views: 344
Re: Speed of light
Typically, if not mentioned, you use the speed of light in a vacuum.
- Sun Oct 20, 2019 11:39 pm
- Forum: Properties of Light
- Topic: Combining Different Equations
- Replies: 8
- Views: 232
Re: Combining Different Equations
Sometimes you are given some info but not others, so in order to solve with the info given you can rearrange them to fit the info you have.
- Sun Oct 20, 2019 11:36 pm
- Forum: Properties of Light
- Topic: Constant for Speed of Light
- Replies: 14
- Views: 558
Re: Constant for Speed of Light
For tests at least, I used the constant given on the front sheet and I got full points for the problem.
- Sun Oct 20, 2019 11:35 pm
- Forum: Properties of Light
- Topic: Unit Conversions
- Replies: 6
- Views: 269
Re: Unit Conversions
I find it easier to convert when you first convert to meters, then to the needed measurement from there.
- Sun Oct 20, 2019 11:33 pm
- Forum: Properties of Light
- Topic: What are the units of hertz
- Replies: 41
- Views: 1942
Re: What are the units of hertz
The unit is 1/s which is essentially s^-1
- Sun Oct 20, 2019 11:32 pm
- Forum: Properties of Electrons
- Topic: Angstrom Conversion
- Replies: 12
- Views: 390
Re: Angstrom Conversion
1 Angstrom is equal to 10^-10 meters
- Fri Oct 11, 2019 4:04 pm
- Forum: Properties of Light
- Topic: Speed of Light
- Replies: 41
- Views: 2707
Re: Speed of Light
3.00 x 10^8 is the speed of light inside a vacuum.
- Fri Oct 11, 2019 4:03 pm
- Forum: Properties of Light
- Topic: Frequency and Hertz
- Replies: 5
- Views: 160
Re: Frequency and Hertz
The unit is simply second^-1 or 1/s.
- Fri Oct 11, 2019 3:58 pm
- Forum: Properties of Light
- Topic: Relationship between lambda and nu
- Replies: 5
- Views: 1091
Re: Relationship between lambda and nu
Based on the equation for the speed of light, c = λ ν, c is a constant, so λ and ν are inversely proportional because they are being multiplied. As one goes up, the other value must go down, and vice versa. For example, if λ, the wavelength goes up in value, the frequency, ν, must respond accordingl...
- Fri Oct 11, 2019 3:55 pm
- Forum: Properties of Light
- Topic: Clarification on Frequency
- Replies: 8
- Views: 410
Re: Clarification on Frequency
Since C=λν, frequency and wavelength are inversely proportional, meaning that as one increases, the other decreases since the speed of light, c, is constant. By decreasing the wavelength, you can increase the frequency.
- Fri Oct 11, 2019 3:53 pm
- Forum: Properties of Light
- Topic: Converting units
- Replies: 8
- Views: 198
Re: Converting units
400nm (1m / 10^9nm) (1 A / 10^-10m) = 4000 A
- Sat Oct 05, 2019 7:51 pm
- Forum: Significant Figures
- Topic: Sig Figs in Mulitstep Problems
- Replies: 10
- Views: 276
Re: Sig Figs in Mulitstep Problems
Personally, I have a calculator that keeps track of all the problems I did previously (TI-84), so what I do is when I am doing work on paper, I will write the answer (throughout the problem not the final answer) with the amount of sig figs that are called for, but when I am calculating the next port...
- Sat Oct 05, 2019 7:42 pm
- Forum: Balancing Chemical Reactions
- Topic: Strategies for Balancing Chemical Equations
- Replies: 12
- Views: 733
Re: Strategies for Balancing Chemical Equations
It might also help to examine the full equation and start with the elemnts or molecules taht appear the least amount of times on each side and work your way up. I agree that this is one of the easiest ways for me to balance equations. Professor Lavelle did also mention this method as his way of bal...
- Sat Oct 05, 2019 7:40 pm
- Forum: Balancing Chemical Reactions
- Topic: When are atoms lost or created?
- Replies: 14
- Views: 1723
Re: When are atoms lost or created?
Atoms cannot be created or destroyed according to the Law of Conservation in chemical reactions, but Professor Lavelle did mention that in the future we will learn about a different type of reaction where atoms can be created of destroyed.
- Sat Oct 05, 2019 7:36 pm
- Forum: Limiting Reactant Calculations
- Topic: Order of atoms in molecules
- Replies: 6
- Views: 218
Re: Order of atoms in molecules
Like most people said already, the order is not very important, but there is a method called the Hill System that states that Carbon atoms are listed first, then Hydrogen, and the rest of the atoms alphabetically.
- Sat Oct 05, 2019 7:30 pm
- Forum: Limiting Reactant Calculations
- Topic: Percent or theoretical yield
- Replies: 14
- Views: 1252
Re: Percent or theoretical yield
Theoretical yield is the calculated amount of yield you get when you plug in values into an equation. Percent yield, however, is the percentage of how much actual yield is produced out of the theoretical yield. Factors that inhibit reactions from producing 100% yield occur because of loss of product...