Search found 47 matches
- Sat Mar 09, 2019 9:44 pm
- Forum: Balancing Redox Reactions
- Topic: OH-
- Replies: 5
- Views: 546
Re: OH-
Use H+ to balance the hydrogen in an acidic solution but use OH- to balance hydrogens in a basic solution
- Sat Mar 09, 2019 9:43 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation number?
- Replies: 12
- Views: 7173
Re: Oxidation number?
We always know that oxygen has a -2 charge and hydrogen always has a +1 charge. Regarding electrochemistry, this is important because if we are given a molecule like XO2H2 with no charge where X is an imaginary atom, we know that X must have an oxidation number of +2
- Sat Mar 09, 2019 9:37 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Redox Reactions
- Replies: 5
- Views: 708
Re: Balancing Redox Reactions
Balance all elements except oxygen and hydrogen. Then balance oxygens by adding h2o. then add twice as much h2o to the opposite Side of reaction. finally balance hydrogens by adding OH-
- Sun Mar 03, 2019 7:23 pm
- Forum: Balancing Redox Reactions
- Topic: Adding H+ and H2O
- Replies: 13
- Views: 2808
Re: Adding H+ and H2O
when doing redox reactions it is most important to make sure the equation is balanced. First balance the important element. Then balance oxygens with H2O. and depending on if it is in an acidic or basic solution, balance hydrogens with H+ or H+ and OH-. you may put coefficients in front of everything
- Sun Feb 24, 2019 11:36 pm
- Forum: Balancing Redox Reactions
- Topic: Problem 14.1, 6th ed.
- Replies: 3
- Views: 376
Re: Problem 14.1, 6th ed.
Although the focus is on the molecules being reduced and oxidized, it is still a chemical reaction and all the elements and charges need to be balanced. As we have done in the past there needs to be the same number of hydrogens on both sides and electrons etc. there are two really good example probl...
- Sun Feb 24, 2019 11:33 pm
- Forum: Balancing Redox Reactions
- Topic: Redox Rxns in Acidic and Basic Solutions
- Replies: 6
- Views: 496
Re: Redox Rxns in Acidic and Basic Solutions
The problem normally tells you if it is happening in an acidic or basic solution
- Sun Feb 24, 2019 11:31 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Redox Rxn Procedures
- Replies: 2
- Views: 278
Re: Balancing Redox Rxn Procedures
No. When balancing a reaction happening in an acidic solution you just balance the oxygens first with h2O and then balance the other side with H+. However, in a reaction in a basic solution you still balance the O in the reaction with H2O. Next you have the add the number of hydrogens to the other s...
- Sun Feb 17, 2019 11:52 pm
- Forum: Calculating Work of Expansion
- Topic: Work without change in volume
- Replies: 8
- Views: 1081
Re: Work without change in volume
if there is no change in volume then there cannot be any work done. remember, it doesnt matter how hard you push against the wall, if it doesnt move no work was done.
- Sun Feb 17, 2019 11:48 pm
- Forum: Calculating Work of Expansion
- Topic: S=0
- Replies: 12
- Views: 1705
Re: S=0
entropy is a state function therefore if the initial entropy is equal to the final entropy then the delta s is 0
- Sun Feb 17, 2019 11:47 pm
- Forum: Calculating Work of Expansion
- Topic: Work
- Replies: 8
- Views: 908
Re: Work
Just like, look at the givens.
- Mon Feb 11, 2019 8:48 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: When to use C=5/2R or C=3/2R
- Replies: 7
- Views: 3051
Re: When to use C=5/2R or C=3/2R
use the 5/2 when pressure is constant.
use 3/2 when volume is constant.
a great example is problem 8.31 in the 6th edition
use 3/2 when volume is constant.
a great example is problem 8.31 in the 6th edition
- Sun Feb 10, 2019 10:32 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Enthalpies of Formation
- Replies: 3
- Views: 327
Re: Standard Enthalpies of Formation
Dr. Lavelle does a great job of providing any constants or equations we need during the test. He normally doesnt ask his students to memorize things like this.
- Sun Feb 10, 2019 10:30 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpy of Phase Changes
- Replies: 4
- Views: 392
Re: Enthalpy of Phase Changes
liquid to gas has a larger enthalpy because more energy has to be put into the system to complete that phase change. When Dr. Lavelle explained why gas burns do more damage than liquid burns it really helped me understand this.
- Sun Feb 10, 2019 10:27 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Units for enthalpy
- Replies: 6
- Views: 722
Re: Units for enthalpy
Joule is the SI unit but sometimes it makes more sense to use Kilo Joules for convince reasons.
- Sun Feb 03, 2019 11:23 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: w=PdeltaV
- Replies: 5
- Views: 630
Re: w=PdeltaV
to calculate volume you multiply area x height. to calculate the area of a cylinder you would find the area of the top and multiply it by the height
- Sun Feb 03, 2019 11:16 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Closed Systems
- Replies: 6
- Views: 454
Re: Closed Systems
both systems can exchange heat however a closed system cannot exchange matter
- Sun Feb 03, 2019 11:16 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Work Formula
- Replies: 5
- Views: 585
Re: Work Formula
P x A x D = P x delta V
Area x distance (height )equals the change in volume. For example if you were to calculate the volume of a cylinder you would find the area of the top and multiply it by the height.
Area x distance (height )equals the change in volume. For example if you were to calculate the volume of a cylinder you would find the area of the top and multiply it by the height.
- Sun Jan 27, 2019 11:59 pm
- Forum: Phase Changes & Related Calculations
- Topic: reversible/irreversible
- Replies: 8
- Views: 781
Re: reversible/irreversible
In reversible reactions the reactants react with other reactants to form products. In a irreversible reaction the reactants react to form the products, which cannot revert back into reactants.
- Sun Jan 27, 2019 11:58 pm
- Forum: Phase Changes & Related Calculations
- Topic: Due date for Discussion Questions
- Replies: 8
- Views: 826
Re: Due date for Discussion Questions
blog posts are due at 11:59, like 2 minutes from now. homework is due in discussion
- Sun Jan 27, 2019 11:52 pm
- Forum: Phase Changes & Related Calculations
- Topic: Phase changes
- Replies: 14
- Views: 1367
Re: Phase changes
you are correct. phase changes like gas to liquid are exothermic and therefore release energy.
- Sun Jan 20, 2019 11:57 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Changes in Temperature
- Replies: 8
- Views: 1107
Re: Changes in Temperature
endothermic- products are favored by a increase in temperature
exothermic- products are favored by a decrease in temperature
exothermic- products are favored by a decrease in temperature
- Sun Jan 20, 2019 11:55 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Is it an acid or a base?
- Replies: 8
- Views: 667
Re: Is it an acid or a base?
an acid donates a proton H+
a base accepts the proton
a base accepts the proton
- Sun Jan 20, 2019 11:54 pm
- Forum: Ideal Gases
- Topic: Calculating the Equilibrium Constant by Approximation
- Replies: 2
- Views: 301
Re: Calculating the Equilibrium Constant by Approximation
ICE table is
initial concentration, change in concentration, equilibrium
initial concentration, change in concentration, equilibrium
- Sun Jan 13, 2019 8:50 pm
- Forum: Ideal Gases
- Topic: Units
- Replies: 19
- Views: 1078
Re: Units
always use kelvins. add 273.15 to Celsius to get kelvins. remember to make sure that the temperature remains the same during the reaction/s.
- Sun Jan 13, 2019 8:44 pm
- Forum: Ideal Gases
- Topic: Question 11.75 (Sixth Edition)
- Replies: 2
- Views: 399
Re: Question 11.75 (Sixth Edition)
Firstly, that chemical equation is incorrect. I think the book messed up. But for part a) NO will increase
b)no, o2 will increase. think of it like a sew saw
b)no, o2 will increase. think of it like a sew saw
- Sun Jan 13, 2019 8:36 pm
- Forum: Ideal Gases
- Topic: K and Q
- Replies: 7
- Views: 459
Re: K and Q
K is the equilibrium constant. Its value is only true once the reaction has reached equilibrium. Q can be calculated any time during the reaction. Regardless of the amount of products and reactants used, K will always be the same.
- Sun Dec 09, 2018 11:35 pm
- Forum: Sigma & Pi Bonds
- Topic: Sigma vs. Pi
- Replies: 11
- Views: 1616
Re: Sigma vs. Pi
the first bond is always a sigma and the next two after that are pi bonds
- Sun Dec 09, 2018 11:34 pm
- Forum: Sigma & Pi Bonds
- Topic: Triple bond?
- Replies: 18
- Views: 1661
Re: Triple bond?
one sigma bond and two pi bonds
- Sun Dec 09, 2018 11:33 pm
- Forum: Sigma & Pi Bonds
- Topic: Double Bonds
- Replies: 9
- Views: 1010
Re: Double Bonds
one sigma bond by default, and a pi bond because its a double
- Sun Dec 09, 2018 11:27 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Oxyacids
- Replies: 4
- Views: 1037
Re: Oxyacids
If the acid has the same base element the strength of the oxyacid depends on the number of oxygens. If the oxyacid has a different base element the stronger oxyacid is the one with a more electronegative base.
- Sun Dec 09, 2018 11:25 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Why HF is a weaker acid than HCl
- Replies: 17
- Views: 16090
Re: Why HF is a weaker acid than HCl
F is too electronegative to have HF be a strong acid. It retains the hydrogen to well and does not fully disassociate in water
- Sun Dec 02, 2018 9:30 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Final
- Replies: 3
- Views: 609
Re: Final
I asked my TA. She said we probably do not need to know this
- Sun Dec 02, 2018 9:28 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: How temperature affects pH
- Replies: 3
- Views: 2545
Re: How temperature affects pH
ph decreases as temperature increases. The molecular vibrations increase which results in the ability of water to ionise and form more hydrogen ions.
- Sun Dec 02, 2018 9:23 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Seesaw
- Replies: 13
- Views: 2008
Re: Seesaw
The trigonal bipyramidal molecular shape normally has bond angle 90 and 120 but because the lone pairs repeal each other the bond angles are <120 and <90
- Sun Nov 25, 2018 11:38 pm
- Forum: Properties of Electrons
- Topic: excitation
- Replies: 2
- Views: 566
Re: excitation
To excite an electron it must be transferred energy. When an electron returns back to its normal state, it releases energy.
- Sun Nov 25, 2018 11:35 pm
- Forum: Properties of Light
- Topic: Test 3
- Replies: 24
- Views: 2117
Re: Test 3
He recently posted this on his website. Test 3 covers "End of Bonding from 3.12 (6 Ed.) and from 2D (7 Ed.); and all of Molecular Shape and Structure (see Syllabus and Outlines for details)."
- Sun Nov 25, 2018 11:32 pm
- Forum: SI Units, Unit Conversions
- Topic: What Unit of Mass to Use?
- Replies: 5
- Views: 914
Re: What Unit of Mass to Use?
It is necessary we use Kilograms when doing calculations. Equations like the momentum p=mv require the mass in kilograms.
- Sun Nov 18, 2018 10:53 pm
- Forum: Ionic & Covalent Bonds
- Topic: London Van Der Waals Force?
- Replies: 5
- Views: 511
Re: London Van Der Waals Force?
Yes, they are synonyms including "induced dipole induced dipole interaction." Van Der Waals forces are caused by the constant fluctuating polarizations of nearby particles causing brief attractions between molecules.
- Sun Nov 18, 2018 10:47 pm
- Forum: Ionic & Covalent Bonds
- Topic: Determining the Difference between Ionic and Covalent Bonds
- Replies: 6
- Views: 664
Re: Determining the Difference between Ionic and Covalent Bonds
If the electronegativity difference between the two atoms is greater than 2, it is likely an ionic bond.
If the electronegativity difference between the two atoms is less than 1.5, it is likely a covalent bond.
If the electronegativity difference between the two atoms is less than 1.5, it is likely a covalent bond.
- Sun Nov 18, 2018 10:42 pm
- Forum: Ionic & Covalent Bonds
- Topic: Hydrogen Bonds and Van Der Waals
- Replies: 4
- Views: 568
Re: Hydrogen Bonds and Van Der Waals
Van Der Waals bonds are constantly occurring due to the fluctuating polarizations of nearby particles. Yes, two atoms experiencing hydrogen bonding can also be experiencing van Der Waals attraction.
- Sun Nov 04, 2018 11:17 pm
- Forum: SI Units, Unit Conversions
- Topic: Kiloelectron volt to Joule
- Replies: 5
- Views: 949
Re: Kiloelectron volt to Joule
1.602 x 10^19 joule = 1 electron volt
- Sun Nov 04, 2018 11:14 pm
- Forum: SI Units, Unit Conversions
- Topic: Significant Figures during Multiple Step Calculations
- Replies: 2
- Views: 507
Re: Significant Figures during Multiple Step Calculations
My TA told us to keep all the digits during the calculations and at the very end to consider sig figs
- Sun Nov 04, 2018 11:13 pm
- Forum: SI Units, Unit Conversions
- Topic: Hz
- Replies: 2
- Views: 341
Re: Hz
Hertz means a single cycle per second
- Sun Oct 28, 2018 8:26 pm
- Forum: Properties of Electrons
- Topic: Coulomb
- Replies: 4
- Views: 655
Re: Coulomb
It is the force of attraction between positive and negative charges. It is responsible for the current generated in a circuit because the free electrons in the conducting wire are attracted to the positive end of the battery.
- Sun Oct 21, 2018 11:55 pm
- Forum: Photoelectric Effect
- Topic: The Photoelectric Effect
- Replies: 3
- Views: 188
Re: The Photoelectric Effect
The discovery of the photoelectric was significant because it proved that light was not only a wavelength but also a particle. It supplied an alternative method of describing light.
- Sun Oct 21, 2018 11:40 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Energy levels of orbitals?
- Replies: 10
- Views: 732
Re: Energy levels of orbitals?
The correct order is s<p<d<f. Keep in mind that an electron traveling from d to s releases more energy than an electron traveling from f to p.
- Sun Oct 21, 2018 11:40 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Energy levels of orbitals?
- Replies: 10
- Views: 732
Re: Energy levels of orbitals?
The correct order is s<p<d<f. Keep in mind that an electron traveling from d to s releases more energy than an electron traveling from f to p.