Search found 47 matches

by 404982241
Sat Mar 09, 2019 9:44 pm
Forum: Balancing Redox Reactions
Topic: OH-
Replies: 5
Views: 60

Re: OH-

Use H+ to balance the hydrogen in an acidic solution but use OH- to balance hydrogens in a basic solution
by 404982241
Sat Mar 09, 2019 9:43 pm
Forum: Balancing Redox Reactions
Topic: Oxidation number?
Replies: 12
Views: 66

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
by 404982241
Sat Mar 09, 2019 9:37 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox Reactions
Replies: 4
Views: 50

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-
by 404982241
Sun Mar 03, 2019 7:23 pm
Forum: Balancing Redox Reactions
Topic: Adding H+ and H2O
Replies: 13
Views: 104

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
by 404982241
Sun Feb 24, 2019 11:36 pm
Forum: Balancing Redox Reactions
Topic: Problem 14.1, 6th ed.
Replies: 3
Views: 17

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...
by 404982241
Sun Feb 24, 2019 11:33 pm
Forum: Balancing Redox Reactions
Topic: Redox Rxns in Acidic and Basic Solutions
Replies: 6
Views: 29

Re: Redox Rxns in Acidic and Basic Solutions

The problem normally tells you if it is happening in an acidic or basic solution
by 404982241
Sun Feb 24, 2019 11:31 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox Rxn Procedures
Replies: 2
Views: 20

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...
by 404982241
Sun Feb 17, 2019 11:52 pm
Forum: Calculating Work of Expansion
Topic: Work without change in volume
Replies: 8
Views: 74

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.
by 404982241
Sun Feb 17, 2019 11:48 pm
Forum: Calculating Work of Expansion
Topic: S=0
Replies: 12
Views: 108

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
by 404982241
Sun Feb 17, 2019 11:47 pm
Forum: Calculating Work of Expansion
Topic: Work
Replies: 8
Views: 67

Re: Work

Just like, look at the givens.
by 404982241
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: 1467

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
by 404982241
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: 34

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.
by 404982241
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: 32

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.
by 404982241
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: 55

Re: Units for enthalpy

Joule is the SI unit but sometimes it makes more sense to use Kilo Joules for convince reasons.
by 404982241
Sun Feb 03, 2019 11:23 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: w=PdeltaV
Replies: 5
Views: 45

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
by 404982241
Sun Feb 03, 2019 11:16 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed Systems
Replies: 6
Views: 38

Re: Closed Systems

both systems can exchange heat however a closed system cannot exchange matter
by 404982241
Sun Feb 03, 2019 11:16 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Work Formula
Replies: 5
Views: 41

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.
by 404982241
Sun Jan 27, 2019 11:59 pm
Forum: Phase Changes & Related Calculations
Topic: reversible/irreversible
Replies: 8
Views: 64

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.
by 404982241
Sun Jan 27, 2019 11:58 pm
Forum: Phase Changes & Related Calculations
Topic: Due date for Discussion Questions
Replies: 8
Views: 86

Re: Due date for Discussion Questions

blog posts are due at 11:59, like 2 minutes from now. homework is due in discussion
by 404982241
Sun Jan 27, 2019 11:52 pm
Forum: Phase Changes & Related Calculations
Topic: Phase changes
Replies: 14
Views: 97

Re: Phase changes

you are correct. phase changes like gas to liquid are exothermic and therefore release energy.
by 404982241
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: 73

Re: Changes in Temperature

endothermic- products are favored by a increase in temperature
exothermic- products are favored by a decrease in temperature
by 404982241
Sun Jan 20, 2019 11:55 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Is it an acid or a base?
Replies: 8
Views: 90

Re: Is it an acid or a base?

an acid donates a proton H+
a base accepts the proton
by 404982241
Sun Jan 20, 2019 11:54 pm
Forum: Ideal Gases
Topic: Calculating the Equilibrium Constant by Approximation
Replies: 2
Views: 36

Re: Calculating the Equilibrium Constant by Approximation

ICE table is
initial concentration, change in concentration, equilibrium
by 404982241
Sun Jan 13, 2019 8:50 pm
Forum: Ideal Gases
Topic: Units
Replies: 19
Views: 164

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.
by 404982241
Sun Jan 13, 2019 8:44 pm
Forum: Ideal Gases
Topic: Question 11.75 (Sixth Edition)
Replies: 2
Views: 44

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
by 404982241
Sun Jan 13, 2019 8:36 pm
Forum: Ideal Gases
Topic: K and Q
Replies: 7
Views: 63

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.
by 404982241
Sun Dec 09, 2018 11:35 pm
Forum: Sigma & Pi Bonds
Topic: Sigma vs. Pi
Replies: 8
Views: 158

Re: Sigma vs. Pi

the first bond is always a sigma and the next two after that are pi bonds
by 404982241
Sun Dec 09, 2018 11:34 pm
Forum: Sigma & Pi Bonds
Topic: Triple bond?
Replies: 11
Views: 119

Re: Triple bond?

one sigma bond and two pi bonds
by 404982241
Sun Dec 09, 2018 11:33 pm
Forum: Sigma & Pi Bonds
Topic: Double Bonds
Replies: 9
Views: 118

Re: Double Bonds

one sigma bond by default, and a pi bond because its a double
by 404982241
Sun Dec 09, 2018 11:27 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Oxyacids
Replies: 4
Views: 67

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.
by 404982241
Sun Dec 09, 2018 11:25 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Why HF is a weaker acid than HCl
Replies: 11
Views: 114

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
by 404982241
Sun Dec 02, 2018 9:30 pm
Forum: Identifying Acidic & Basic Salts
Topic: Final
Replies: 3
Views: 201

Re: Final

I asked my TA. She said we probably do not need to know this
by 404982241
Sun Dec 02, 2018 9:28 pm
Forum: Calculating the pH of Salt Solutions
Topic: How temperature affects pH
Replies: 3
Views: 239

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.
by 404982241
Sun Dec 02, 2018 9:23 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Seesaw
Replies: 13
Views: 167

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
by 404982241
Sun Nov 25, 2018 11:38 pm
Forum: Properties of Electrons
Topic: excitation
Replies: 2
Views: 46

Re: excitation

To excite an electron it must be transferred energy. When an electron returns back to its normal state, it releases energy.
by 404982241
Sun Nov 25, 2018 11:35 pm
Forum: Properties of Light
Topic: Test 3
Replies: 24
Views: 344

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)."
by 404982241
Sun Nov 25, 2018 11:32 pm
Forum: SI Units, Unit Conversions
Topic: What Unit of Mass to Use?
Replies: 5
Views: 177

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.
by 404982241
Sun Nov 18, 2018 10:53 pm
Forum: Ionic & Covalent Bonds
Topic: London Van Der Waals Force?
Replies: 5
Views: 91

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.
by 404982241
Sun Nov 18, 2018 10:47 pm
Forum: Ionic & Covalent Bonds
Topic: Determining the Difference between Ionic and Covalent Bonds
Replies: 6
Views: 96

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.
by 404982241
Sun Nov 18, 2018 10:42 pm
Forum: Ionic & Covalent Bonds
Topic: Hydrogen Bonds and Van Der Waals
Replies: 4
Views: 74

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.
by 404982241
Sun Nov 04, 2018 11:17 pm
Forum: SI Units, Unit Conversions
Topic: Kiloelectron volt to Joule
Replies: 5
Views: 174

Re: Kiloelectron volt to Joule

1.602 x 10^19 joule = 1 electron volt
by 404982241
Sun Nov 04, 2018 11:14 pm
Forum: SI Units, Unit Conversions
Topic: Significant Figures during Multiple Step Calculations
Replies: 2
Views: 64

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
by 404982241
Sun Nov 04, 2018 11:13 pm
Forum: SI Units, Unit Conversions
Topic: Hz
Replies: 2
Views: 53

Re: Hz

Hertz means a single cycle per second
by 404982241
Sun Oct 28, 2018 8:26 pm
Forum: Properties of Electrons
Topic: Coulomb
Replies: 4
Views: 111

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.
by 404982241
Sun Oct 21, 2018 11:55 pm
Forum: Photoelectric Effect
Topic: The Photoelectric Effect
Replies: 3
Views: 48

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.
by 404982241
Sun Oct 21, 2018 11:40 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Energy levels of orbitals?
Replies: 10
Views: 70

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.
by 404982241
Sun Oct 21, 2018 11:40 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Energy levels of orbitals?
Replies: 10
Views: 70

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.

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