Search found 97 matches

by Zaynab Hashm 2I
Tue Feb 25, 2020 6:58 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anode and Cathode
Replies: 4
Views: 8

Re: Anode and Cathode

anode is the electrode where oxidation occurs and cathode is the electrode where reduction occurs;
electrons flow from anode (-) to cathode (+)
by Zaynab Hashm 2I
Mon Feb 24, 2020 10:14 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: electrolytic cells
Replies: 3
Views: 9

Re: electrolytic cells

electrolytic cells are used in the process of electrolysis which drives a non-spontaneous redox reaction to decompose chemical compounds using electrical energy
by Zaynab Hashm 2I
Mon Feb 24, 2020 10:11 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Difference in G's
Replies: 2
Views: 10

Re: Difference in G's

I believe the only difference is that ΔG° is ONLY in standard conditions (like it is constant/unchanging for specific measures), however ΔG is not specific, it changes depending on other variables!
by Zaynab Hashm 2I
Wed Feb 19, 2020 11:09 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anode and Cathode position
Replies: 5
Views: 20

Re: Anode and Cathode position

just to make sure, you can double check to see which side is oxidized/negative (=anode) and which side is reduced/positive (=cathode)
by Zaynab Hashm 2I
Wed Feb 19, 2020 11:05 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anode and Cathode
Replies: 6
Views: 15

Re: Anode and Cathode

electrons always flow from the anode (-) to the cathode (+)
in other words, electrons always flow from the oxidation half cell to the reduction half cell.
by Zaynab Hashm 2I
Wed Feb 19, 2020 11:01 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Potential difference between electrodes
Replies: 3
Views: 12

Re: Potential difference between electrodes

I am not too sure, but I hope this helps a little;

E is the electromotive force (EMF) which equals the potential difference when there is no current flow,
since i represents current, it shows that as the current tends to 0, the potential difference is at a maximum.
by Zaynab Hashm 2I
Wed Feb 19, 2020 10:51 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Battery Dying
Replies: 4
Views: 18

Re: Battery Dying

a battery would die at equilibrium because there will no longer be a flow of charge/electrons between the anode and cathode; using a salt bridge (or porous disk) would prevent that
by Zaynab Hashm 2I
Wed Feb 19, 2020 10:45 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Gibbs free energy
Replies: 5
Views: 14

Re: Gibbs free energy

ΔG denotes conditions that are not at standard state
ΔG° denotes conditions that are at standard state

*standard state: 1 M, 1 atm, and 298 K (= 25°C)
by Zaynab Hashm 2I
Thu Feb 13, 2020 10:23 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: reaction entropy
Replies: 7
Views: 24

Re: reaction entropy

we use, ΔS° = ΣS°(products) - ΣS°(reactants), and i think we can also calculate ΔS using some of the formulas found on the formula sheet, but that depends on what is known/unknown and the system of the reaction
by Zaynab Hashm 2I
Thu Feb 13, 2020 9:57 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4.15
Replies: 1
Views: 26

Re: 4.15

when calculating ΔH(rxn), we find that all except for ΔH(zinc) in the products is not in its most stable state and therefore not equal to 0. zinc is also the limiting reagent in that reaction, after finding ΔH(rxn) multiply it by moles of zinc which you can find by dividing by molar mass of zinc. th...
by Zaynab Hashm 2I
Thu Feb 13, 2020 9:40 pm
Forum: Ideal Gases
Topic: initial values
Replies: 6
Views: 23

Re: initial values

usually in the question, the initial values are given for both P and V, so make sure to use all the initial values (of all variables) at once in the equation to find n
by Zaynab Hashm 2I
Thu Feb 13, 2020 9:37 pm
Forum: Phase Changes & Related Calculations
Topic: Relation to entropy?
Replies: 3
Views: 15

Re: Relation to entropy?

from lecture notes; "molecules in gaseous phase occupy many more states than liquid and solid"

W(g) > W(l) > W(s) and since S = Kbxln(W) then S(g) > S(l) > S(s)
by Zaynab Hashm 2I
Thu Feb 13, 2020 9:33 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: How do I do? [ENDORSED]
Replies: 2
Views: 35

Re: How do I do? [ENDORSED]

Gibbs Free Energy can be calculated by using:

1) ∆G = ∆H – T∆S
2) ∆G = – RT ln(K)
3) ∆G = sum of G(products) - sum of G(reactants)
4) Hess's Method (adding or subtracting ∆G(rxn))
by Zaynab Hashm 2I
Thu Feb 06, 2020 1:36 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U equals zero
Replies: 7
Views: 40

Re: Delta U equals zero

it would be for an isothermal reaction when the temperature is constant
by Zaynab Hashm 2I
Thu Feb 06, 2020 1:31 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Insulated system
Replies: 5
Views: 20

Re: Insulated system

we can relate insulation to the effects of temperature on entropy; if a system is insulated, heat cannot be transferred (so temperature won't increase), and therefore there won't be a change in entropy.. hence we can focus instead on how the pressure and volume of such a system would affect entropy
by Zaynab Hashm 2I
Tue Feb 04, 2020 6:21 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Statistical Entropy
Replies: 1
Views: 9

Re: Statistical Entropy

in general, entropy is a measure of randomness

statistical is when you measure the randomness based on the different microstates that affects entropy
thermodynamic is when you measure the randomness based on the heat transfer that affects entropy
by Zaynab Hashm 2I
Tue Feb 04, 2020 12:22 am
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Reversible Reactions
Replies: 1
Views: 6

Re: Reversible Reactions

reversible reactions are when the reactants that formed the products can go back the other way, so that the products can reform the reactants however, that is not possible for irreversible reactions, where the products cannot reform their reactants (for example, most combustion reactions) in other w...
by Zaynab Hashm 2I
Tue Feb 04, 2020 12:18 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat capacity
Replies: 3
Views: 13

Re: Heat capacity

heat capacity is the amount of heat energy required to raise the temperature of 1 g of a substance by 1 K constant volume heat capacity; there is no work of expansion, so all heat is contained and used to raise the temperature constant pressure heat capacity; there is work of expansion, so some of t...
by Zaynab Hashm 2I
Wed Jan 29, 2020 6:09 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: memorize
Replies: 6
Views: 17

Re: memorize

I believe some of the important ones are already included on the formula sheet
by Zaynab Hashm 2I
Wed Jan 29, 2020 6:05 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Deriving Equation
Replies: 3
Views: 25

Re: Deriving Equation

delta U = delta H - P delta V comes from the equation U = q + w

since q = delta H (change in enthalpy), and w = - P delta V,
when you plug those in instead of q and w, you will get delta U = delta H - P delta V
by Zaynab Hashm 2I
Wed Jan 29, 2020 6:01 pm
Forum: Phase Changes & Related Calculations
Topic: energy of a system
Replies: 4
Views: 39

Re: energy of a system

Before releasing the compressed air, the system will have a high internal energy due to the high pressure inside. After releasing, there will be a work of expansion on the surroundings, and this in turn will decrease the internal energy of the system. In other words, the system loses energy.
by Zaynab Hashm 2I
Tue Jan 28, 2020 11:52 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Delta T
Replies: 4
Views: 17

Re: Delta T

an exothermic reaction will release heat which will raise the temperature of the surroundings and an endothermic reaction will therefore do the opposite if heat is released for exothermic rxns why is delta t negative? for exothermic reactions, delta T is positive as temperature increases (due to th...
by Zaynab Hashm 2I
Tue Jan 28, 2020 11:50 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Delta T
Replies: 4
Views: 17

Re: Delta T

delta T (change in temperature) calculated for a system shows whether a reaction is endothermic (absorbs energy) or exothermic (releases energy) if a reaction is endothermic, it absorbs the heat energy, therefore decreases (-) the overall temperature of the system if a reaction is exothermic, it rel...
by Zaynab Hashm 2I
Fri Jan 24, 2020 4:51 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Steam
Replies: 5
Views: 17

Re: Steam

steam has "stored" energy in its molecules as they move freely;
when steam condenses upon contact with skin, it release said energy because of the difference in temperatures

simply put, steam can cause severe burns due to its high heat energy
by Zaynab Hashm 2I
Fri Jan 24, 2020 4:19 pm
Forum: Ideal Gases
Topic: Inert Gas
Replies: 12
Views: 32

Re: Inert Gas

inert gas is another term used for noble gas as these gases do not undergo chemical reactions under a set of given conditions (=unreactive)
by Zaynab Hashm 2I
Fri Jan 24, 2020 4:13 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Pressure and Enthalpy
Replies: 5
Views: 21

Re: Pressure and Enthalpy

when pressure increases, enthalpy increases; and when pressure decreases, enthalpy decreases
by Zaynab Hashm 2I
Fri Jan 24, 2020 4:10 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pka
Replies: 4
Views: 18

Re: pka

the higher the pKa, the weaker the acid (less acidic)
by Zaynab Hashm 2I
Fri Jan 24, 2020 4:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Percent Ionization
Replies: 12
Views: 41

Re: Percent Ionization

% ionization = (acid ionized/initial acid) x 100%

so the value of x divided by the initial molarity, multiplied by a 100%
by Zaynab Hashm 2I
Fri Jan 17, 2020 7:01 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: 6B.9
Replies: 1
Views: 14

Re: 6B.9

I'm not sure, but your answer is the same as what I am getting!

6.67x10^-15 seems right because Kw = [H3O+][OH-] = 10^-14

and when you multiply the concentrations, you only get the right value if you use 6.67x10^-15 instead of 1.50x10^-14
by Zaynab Hashm 2I
Fri Jan 17, 2020 6:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Exercise 6A.19
Replies: 4
Views: 42

Exercise 6A.19

6A.19 is asking to calculate the molar concentration of OH- given the molar concentration of H3O+, in part c) [H3O+] = 3.1 mol.L^-1 using [H3O+] [OH-] = 10^-14 (Kw), i keep getting 3.2 x 10^-15 mol.L^-1 (i checked that it is 3.2 x 10^-12 mol.L^-1 in the solution manual) would that be a solution manu...
by Zaynab Hashm 2I
Fri Jan 17, 2020 6:43 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Different types of acids/bases
Replies: 3
Views: 24

Re: Different types of acids/bases

Bronsted-Lowry Acid: H+ donor
Bronsted-Lowry Base: H+ acceptor

Arrhenius Acid: produces H+ in H2O
Arrhenius Base: produces OH- in H2O

Lewis Acid: electron pair acceptor
Lewis Base: electron pair donor

hope this helps a little!
by Zaynab Hashm 2I
Fri Jan 17, 2020 6:29 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH for weak acids
Replies: 5
Views: 23

Re: pH for weak acids

pH is a measure of the concentration of H3O+ or H+, so it basically measures the concentration of hydronium ions in a solution. strong acids dissociate/ionize way more compared to weak acids, and therefore release more H+. since pH measures the concentration of H+ in the solution; 1. stronger acids ...
by Zaynab Hashm 2I
Wed Jan 15, 2020 2:22 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Calculating Q
Replies: 16
Views: 45

Re: Calculating Q

We calculate Q the same way we calculate K, and we account for both aqueous and gaseous states. However, liquids and solids are disregarded when calculating the constants. The only difference is that Q indicates the change in the reaction/system at any time before reaching equilibrium, but K is at e...
by Zaynab Hashm 2I
Wed Jan 15, 2020 2:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.39
Replies: 1
Views: 35

Re: 5.39

Solution Manual Errors (7th Edition) have been posted on Professor Lavelle’s website:

https://lavelle.chem.ucla.edu/wp-conten ... rs_7Ed.pdf

I’m not quite sure where you made a mistake, but if you don’t find the error in this PDF, try to solve it again.
by Zaynab Hashm 2I
Fri Jan 10, 2020 4:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Exercise 5G.1
Replies: 4
Views: 17

Exercise 5G.1

5G.1 is true/false c) if one starts with a higher pressure of reactant, the equilibrium constant will be larger d) if one starts with a higher concentrations of reactants, the equilibrium concentrations of the products will be larger my question is, why is c) false and why is d) true, what would the...
by Zaynab Hashm 2I
Fri Jan 10, 2020 3:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: PCl5 example in lecture
Replies: 2
Views: 22

PCl5 example in lecture

During today's lecture, a student asked what would we change X to if PCl3 had a stoichiometric coefficient of 2 instead of 1, I think Professor Lavelle said that it would be 2X. Is that right? (I wanted to check if my notes were correct!) Also, when would it be 2X^2 for PCl3? (he mentioned it, but I...
by Zaynab Hashm 2I
Fri Jan 10, 2020 3:16 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: K vs Q
Replies: 9
Views: 51

K vs Q

can someone please explain the reason why when;

1) Q<K, there is more reactant

2) Q>K, there is more product

anything explaining what results in Q<K or Q>K would help!
by Zaynab Hashm 2I
Fri Jan 10, 2020 3:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Example 5I.4
Replies: 4
Views: 23

Re: Example 5I.4

If you mean why we have to use partial pressure, it's because the question mentions that they're in a gas-phase equilibrium. We use partial pressure for gases.
by Zaynab Hashm 2I
Fri Jan 10, 2020 2:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K expression involving solids/liquids
Replies: 7
Views: 40

K expression involving solids/liquids

why do we not include the concentrations of solids or liquids in the equilibrium constant expression, k?

* do we only account for concentrations in the aqueous state?
by Zaynab Hashm 2I
Fri Dec 06, 2019 11:23 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: HW 9C.9
Replies: 2
Views: 23

Re: HW 9C.9

to help you figure those out, you must know that;

in c (en) = bidentate
in d (edta) = hexadentate

*count as binding sites to get the coordination number
by Zaynab Hashm 2I
Fri Dec 06, 2019 11:18 pm
Forum: Dipole Moments
Topic: London Dispersion Forces
Replies: 4
Views: 37

Re: London Dispersion Forces

yes, every molecule has london dispersion forces
by Zaynab Hashm 2I
Tue Dec 03, 2019 12:34 am
Forum: Naming
Topic: Cobalt vs Cobaltate
Replies: 3
Views: 25

Re: Cobalt vs Cobaltate

we only add the suffix -ate to indicate that the coordination compound has a net negative charge
by Zaynab Hashm 2I
Mon Dec 02, 2019 11:47 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: H2O as a monodenate ligand
Replies: 1
Views: 18

Re: H2O as a monodenate ligand

I believe it's because both lone pairs are on the same (one) oxygen atom, so there would only be one binding site for the metal (since in this case, the metal would only bind to one atom)
by Zaynab Hashm 2I
Mon Dec 02, 2019 11:41 pm
Forum: Naming
Topic: [CO(SO4)(NH3)5]+
Replies: 2
Views: 21

Re: [CO(SO4)(NH3)5]+

pentaamminesulfatocobalt (III) ion
by Zaynab Hashm 2I
Wed Nov 27, 2019 12:30 am
Forum: Lewis Acids & Bases
Topic: Identifying Acids and Bases
Replies: 8
Views: 36

Re: Identifying Acids and Bases

in addition to the answer above, I have noticed two more things:

weak acids usually have carbon or phosphorus in them (ex. carboxyl group COOH)
weak bases usually have nitrogen in them (ex. amine group NH2 or NH3)

but again, this ISN'T a guideline you should always depend on!
by Zaynab Hashm 2I
Wed Nov 27, 2019 12:03 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: 9c7
Replies: 1
Views: 23

Re: 9c7

a chelate consists of a central metal atom binding to a ligand (polydentate: meaning it has multiple binding sites) in a ring structure *a ligand can only chelate a metal atom if it has multiple binding sites (=polydentate) p.s. in that specific question, you must know that the binding sites must be...
by Zaynab Hashm 2I
Tue Nov 26, 2019 11:41 pm
Forum: Lewis Acids & Bases
Topic: Neutralization reaction
Replies: 1
Views: 39

Re: Neutralization reaction

**i noticed this was question J.7 (b) zinc nitrite (not zinc nitrate) a neutralization reaction is a reaction between an acid and a base to produce a salt and water we know the products: the salt produced is zinc nitrite which is written as Zn(NO2)2 and water H2O now, we have to figure out the acid ...
by Zaynab Hashm 2I
Tue Nov 26, 2019 11:09 pm
Forum: Lewis Acids & Bases
Topic: writing chemical equation
Replies: 1
Views: 25

Re: writing chemical equation

that appears to be the net chemical equation

C5H5NHCl dissociates and forms Cl- ions that appear on both sides of the equation, but because the Cl- ions don't affect the overall interaction with water, they would be "removed" from both sides in the net chemical equation
by Zaynab Hashm 2I
Tue Nov 26, 2019 11:01 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic spectroscopy vs. molecular spectroscopy
Replies: 1
Views: 36

Re: Atomic spectroscopy vs. molecular spectroscopy

I think it's actually the same concept for both, but the difference would be;
atomic spectroscopy: of atoms (a single atom)
molecular spectroscopy: of molecules (two or more atoms)
by Zaynab Hashm 2I
Thu Nov 21, 2019 12:37 am
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Homework 3F3
Replies: 5
Views: 43

Re: Homework 3F3

even if you put them opposite to each other, remember that tetrahedral structures have bond angle 109.5 degrees, and so they won't even be in complete symmetry to cancel the dipole moments here's a tip; all carbon atom tetrahedral structures are polar, unless the carbon atom is surrounded by 4 atoms...
by Zaynab Hashm 2I
Tue Nov 19, 2019 6:16 pm
Forum: Hybridization
Topic: Hybridization of H2
Replies: 2
Views: 21

Re: Hybridization of H2

hybridization is a concept used for mixing or overlapping s and p orbitals, and since hydrogen only has a 1s orbital, it doesn't hybridize.
by Zaynab Hashm 2I
Tue Nov 19, 2019 6:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.19
Replies: 2
Views: 26

Re: 2E.19

Be would form two bonds (one with each CH3).

If it asked about the shape with respect to the central atom (Be), it would be linear (this would also be the shape of the overall structure).
BUT,
If it asked about the shape with respect to the carbon atom, it would be tetrahedral.
by Zaynab Hashm 2I
Tue Nov 19, 2019 4:38 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: diethyl ether and butanol
Replies: 1
Views: 15

Re: diethyl ether and butanol

because diethyl ether can't form hydrogen bonds with other diethyl ether molecules, but butanol can, and so the more the intermolecular forces, the bigger the attraction, and it gets harder to break the molecules apart (leading to a higher boiling point)
by Zaynab Hashm 2I
Fri Nov 15, 2019 8:34 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 3
Views: 33

Bond Angles

can someone please explain why bond angles may differ slightly for molecules with the same formula and general shape?

thanks in advance!
by Zaynab Hashm 2I
Fri Nov 15, 2019 8:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: clouds of electrons
Replies: 3
Views: 31

Re: clouds of electrons

I believe you would count that as a one region of electron density
by Zaynab Hashm 2I
Tue Nov 12, 2019 5:33 pm
Forum: Octet Exceptions
Topic: Octet Exceptions
Replies: 2
Views: 38

Re: Octet Exceptions

H and He only require 2 electrons for their highest energy shell to be full (they only have 1s that needs to be filled with only 2 electrons rather than 8). Li and Be are metals that tend to lose electrons rather than gain them to get a positive charge, hence going back to the lower noble gas config...
by Zaynab Hashm 2I
Tue Nov 12, 2019 5:29 pm
Forum: Bond Lengths & Energies
Topic: Bond lengths in molecules
Replies: 7
Views: 46

Re: Bond lengths in molecules

bond length in increasing order is: triple bond < double bond < single bond
by Zaynab Hashm 2I
Tue Nov 12, 2019 4:45 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: melting points
Replies: 5
Views: 29

Re: melting points

NaCl is an ionic bond, HCl is a covalent bond. Ionic bonds are stronger than coverlet bonds, and due to the higher attractions, they have a higher melting point.
by Zaynab Hashm 2I
Thu Nov 07, 2019 2:34 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: London Forces
Replies: 1
Views: 23

Re: London Forces

yes, because the rod-shaped molecules have a greater surface area than spherical-shaped molecules, allowing more contact points for attraction forces between molecules (more attraction forces = stronger).
by Zaynab Hashm 2I
Thu Nov 07, 2019 2:28 pm
Forum: SI Units, Unit Conversions
Topic: Kj
Replies: 6
Views: 60

Re: Kj

yes, kilo is always 10^3 in unit conversions. 1 kJ = 1000 J.
by Zaynab Hashm 2I
Thu Nov 07, 2019 2:26 pm
Forum: SI Units, Unit Conversions
Topic: Photons
Replies: 3
Views: 55

Re: Photons

eV (electron volt) is a unit of energy which equals to approximately 1.602×10−19 J, and is commonly used to measure the energy of particles including photons.
by Zaynab Hashm 2I
Thu Nov 07, 2019 2:23 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: Dispersion forces
Replies: 6
Views: 40

Re: Dispersion forces

polarizability is the measure of how easily the electron cloud is distorted, so the higher the polarizability, the stronger the dispersion force because the larger electron clouds allow for more effective overlap resulting in a higher attraction between the molecules.
by Zaynab Hashm 2I
Thu Nov 07, 2019 2:10 pm
Forum: Trends in The Periodic Table
Topic: Polarizability
Replies: 4
Views: 38

Re: Polarizability

generally the trend for polarizability is related to the atomic radii trend; it increases down a group and decreases across a period on the periodic table.

the larger the anion, the more polarizable; they would be arranged like so O2-<N3-<Cl-<Br-
by Zaynab Hashm 2I
Wed Oct 30, 2019 11:31 pm
Forum: Trends in The Periodic Table
Topic: Does H have the highest ionization energy?
Replies: 4
Views: 33

Re: Does H have the highest ionization energy?

ionization energy increases across a period and decreases down a group, so if you look at the periodic table it is clear that helium is the element that has the highest first ionization energy
by Zaynab Hashm 2I
Wed Oct 30, 2019 11:19 pm
Forum: Resonance Structures
Topic: dislocation
Replies: 1
Views: 35

Re: dislocation

Do you mean delocalization of electrons? If yes, it is when the electric charge is spread over the atoms in a certain bond (usually over a few of the atoms and not all of them) as the electrons can move freely and transfer within the structure. For example, in the Lewis structure of CN2(2-) rather t...
by Zaynab Hashm 2I
Tue Oct 29, 2019 7:27 pm
Forum: Ionic & Covalent Bonds
Topic: Strength of ionic and covalent bonds
Replies: 2
Views: 18

Re: Strength of ionic and covalent bonds

Generally, ionic bonds are stronger than covalent bonds as they are harder to break.
Double bonds are stronger than single bonds as they are shorter (the shorter the bond, the stronger).
by Zaynab Hashm 2I
Tue Oct 29, 2019 7:25 pm
Forum: Formal Charge and Oxidation Numbers
Topic: FC Charge and Stability
Replies: 2
Views: 29

Re: FC Charge and Stability

Yes, for example when a compound has an overall charge on it like the 2- in SO3(2-); where the sulfur and one of the oxygen atoms will have a formal charge of 0 , and the other two atoms of oxygen will have a formal charge of -1 each. We must try to get the FC that is closest to zero to make sure it...
by Zaynab Hashm 2I
Tue Oct 29, 2019 7:12 pm
Forum: Octet Exceptions
Topic: Can P,S,Cl have less than 8 electrons?
Replies: 3
Views: 28

Re: Can P,S,Cl have less than 8 electrons?

I think they could, but they wouldn't be stable then! Since they can use their d-orbitals to expand on the octet rule, these elements can have more than 8 valence electrons to be in their most stable form.
by Zaynab Hashm 2I
Fri Oct 25, 2019 1:57 pm
Forum: Ionic & Covalent Bonds
Topic: Resonance
Replies: 7
Views: 42

Re: Resonance

Can someone explain what resonance is and what the importance of it is? Resonance is a way of describing bonding that might form different structures of a certain molecule or ion where the chemical connectivity is the same but the electrons are distributed differently around the structure. It basic...
by Zaynab Hashm 2I
Thu Oct 24, 2019 6:59 pm
Forum: Trends in The Periodic Table
Topic: Aufbau Principle
Replies: 11
Views: 84

Re: Aufbau Principle

What kind of questions might there be regarding the Aufbau Principle on a test? Questions regarding the electron configurations of elements. So you must be able to know the principles in order to determine the correct electron configurations or to figure out whether or not the electron is in a grou...
by Zaynab Hashm 2I
Mon Oct 21, 2019 8:46 pm
Forum: Trends in The Periodic Table
Topic: 2nd Ionization Energy
Replies: 7
Views: 44

Re: 2nd Ionization Energy

It is much easier to remove an electron from a neutral atom using the first ionization energy, however, after you take the first electron, the atom becomes positive in charge. The positive charge of the atom creates a higher attraction that becomes rather hard to break apart. Therefore, it requires ...
by Zaynab Hashm 2I
Mon Oct 21, 2019 8:29 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electrostatic potential energy
Replies: 2
Views: 35

Re: Electrostatic potential energy

This is the equation used to show the electrostatic (Coulomb) potential energy for multi-electron atoms (basically non-hydrogen atoms). Each q indicates a charge (typically different level charges), and the r is the distance between the charges. The equation shows that the charges and the distance b...
by Zaynab Hashm 2I
Mon Oct 21, 2019 8:25 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity Trends
Replies: 5
Views: 43

Electron Affinity Trends

I know that atomic radii increase down a group, but decrease across a period; and ionization energy decrease down a group, but increase across a period.

My question is what is the case for electron affinity? What would be the trend down a group and across a period? And why?

Thanks in advance!
by Zaynab Hashm 2I
Wed Oct 16, 2019 7:11 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals
Replies: 4
Views: 40

Re: Orbitals

These can be described by quantum numbers; specifically the magnetic quantum number (ml). The Px, Py, and Pz describe the orientation (on the 3D axis).

For example; Px has ml = -1, Py has ml = 1, and Pz has ml = 0.

Hope that helps!
by Zaynab Hashm 2I
Wed Oct 16, 2019 7:01 pm
Forum: Properties of Electrons
Topic: Question About Electron State
Replies: 3
Views: 33

Re: Question About Electron State

It's basically the orbital. The 2 is the shell (energy and size) determined by the principle quantum number (n), the p is the subshell (shape) determined by the angular momentum quantum number (l), the x is the orbital (orientation) of a subshell determined by the magnetic quantum number (ml).
by Zaynab Hashm 2I
Tue Oct 15, 2019 10:58 pm
Forum: Properties of Light
Topic: Homework help
Replies: 4
Views: 55

Re: Homework help

use the following equation; λ = h/mv to find the wavelength.

m is mass of electron which = 9.109 x 10^-31 kg
v is the speed given which = 3.6 x 10^6 m/s
by Zaynab Hashm 2I
Tue Oct 15, 2019 3:34 pm
Forum: DeBroglie Equation
Topic: 1B.27
Replies: 1
Views: 39

Re: 1B.27

We're actually supposed to use Δv= 10, there's an error in the solutions manual for this question!
by Zaynab Hashm 2I
Tue Oct 15, 2019 3:30 pm
Forum: DeBroglie Equation
Topic: 1B.9 HW Question
Replies: 8
Views: 84

Re: 1B.9 HW Question

You first convert the Watts to Joules of energy by multiplying 32 Watts (J.s^-1) by time which is 2 seconds; the units cancel and you're left with Joules of total energy (lamp). Then use E = hc/λ to find the energy of a photon. Now you can divide the total energy (64 J) by the energy of a photon (gi...
by Zaynab Hashm 2I
Tue Oct 15, 2019 3:16 pm
Forum: Properties of Light
Topic: 1A. 15 HW Problem
Replies: 2
Views: 32

Re: 1A. 15 HW Problem

The 102.6 nm here indicates the wavelength (λ) which you'll need to use in the c = λv equation to find the unknown frequency. Then you can plug the values in the Rydberg equation to solve for n2.
by Zaynab Hashm 2I
Tue Oct 15, 2019 2:44 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Explanation of Shells
Replies: 2
Views: 35

Re: Explanation of Shells

An electron shell is the outside part of an atom that surrounds the atomic nucleus (almost like an outer cloud), and it is where electrons are found. The wave function for an electron in an atom is basically an atomic orbital where electrons are found, that's why there's a high probability of findin...
by Zaynab Hashm 2I
Tue Oct 15, 2019 2:41 pm
Forum: DeBroglie Equation
Topic: Textbook Question 1B21
Replies: 3
Views: 36

Re: Textbook Question 1B21

You should be able to get the answer first converting mass into kilograms (=0.146 kg), and the speed which is given in miles per hour to meters per seconds (=41.1 m/s), (make sure you're using the right converting factors). Then use De Broglie's equation with the given or known values in order to so...
by Zaynab Hashm 2I
Thu Oct 10, 2019 4:41 pm
Forum: Empirical & Molecular Formulas
Topic: Homework F9
Replies: 4
Views: 55

Re: Homework F9

You don't always have to multiply it by 3, it could be 2, for example. You just have to make sure you multiply by the smallest number possible to get whole integers.
by Zaynab Hashm 2I
Thu Oct 10, 2019 4:33 pm
Forum: Properties of Light
Topic: Online Modules #28A
Replies: 2
Views: 31

Re: Online Modules #28A

You use the formula E (kinetic energy) = 1/2mv^2. The velocity is already given, but the mass you should use is the mass of an electron (a constant) which is 9.11 × 10^-31 kilograms.
by Zaynab Hashm 2I
Thu Oct 10, 2019 3:51 pm
Forum: Properties of Light
Topic: Energy of light
Replies: 4
Views: 48

Re: Energy of light

Yes, the shorter the wavelength, the higher the energy; and the higher the frequency, the higher the energy. We get that by the inversely proportional relationship between wavelength and frequency. You can figure out through different formulas that there is a specific constant so only the wavelength...
by Zaynab Hashm 2I
Thu Oct 10, 2019 3:45 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: ground/excited electron states
Replies: 2
Views: 77

Re: ground/excited electron states

You basically have to follow certain rules/principles to see which state they would be in. If they follow the rules/principles, they are in a ground state, if not, then they are in an excited state. For 1E.7, you are given four different examples; the rule to be followed in order to be considered in...
by Zaynab Hashm 2I
Thu Oct 10, 2019 3:21 pm
Forum: Empirical & Molecular Formulas
Topic: Converting from grams to percentage
Replies: 11
Views: 110

Re: Converting from grams to percentage

When it is already given in a percentage (of a hundred), we assume it is a 100g sample and use the numbers as they are given. But when you are given a sample of a different mass that is not 100g total, then you have to convert the individual masses by finding their mass percent composition for easie...
by Zaynab Hashm 2I
Wed Oct 09, 2019 9:07 pm
Forum: Quantum Numbers and The H-Atom
Topic: Frequency
Replies: 15
Views: 145

Re: Frequency

ATingin_3I wrote:Also speaking of frequency, is frequency always measured in terms of Hz?

Yes, the unit used for measuring frequency is Hertz (Hz), which is the same as (s^-1).
by Zaynab Hashm 2I
Wed Oct 09, 2019 8:13 pm
Forum: Quantum Numbers and The H-Atom
Topic: Frequency
Replies: 15
Views: 145

Re: Frequency

I think that the frequency is directly proportional to the difference in energy levels. They both increase or decrease together; you can tell from ΔE = hv.
by Zaynab Hashm 2I
Wed Oct 09, 2019 4:42 pm
Forum: Properties of Electrons
Topic: electron energy [ENDORSED]
Replies: 7
Views: 57

Re: electron energy [ENDORSED]

I am not sure what you mean by the electrons either lose energy or decrease. However, when electrons move (jump) from a lower energy level to a higher one, they absorb energy (gain), and when electrons move (jump) from a higher energy level to a lower one, they emit energy (lose).

Hope that helps!
by Zaynab Hashm 2I
Tue Oct 08, 2019 10:40 pm
Forum: Balancing Chemical Reactions
Topic: state of acids
Replies: 3
Views: 46

Re: state of acids

If you are talking about the state in written chemical equations, they are usually aqueous (aq). That is because most acids dissolve to form aqueous solutions.
by Zaynab Hashm 2I
Thu Oct 03, 2019 7:52 pm
Forum: Molarity, Solutions, Dilutions
Topic: CuSO4 vs CuSO4 [tex]\cdot[/tex] 5H2O
Replies: 4
Views: 76

Re: CuSO4 vs CuSO4 [tex]\cdot[/tex] 5H2O

Hi Zaynab, Thanks for your help. How is that different than writing in a balanced chemical equation CuSO4 + H2O --> products ? To balance such equations just go with how you usually balance equations, but leave the H and O to the very last. Since you usually have a number in front of the H2O in the...
by Zaynab Hashm 2I
Mon Sep 30, 2019 8:51 pm
Forum: General Science Questions
Topic: Order of Elements When Writing Out a Compound
Replies: 8
Views: 130

Re: Order of Elements When Writing Out a Compound

Typically,if carbon is present it comes first, then hydrogen, and then the others alphabetically. Cations are also written first before anions, so positive before negative in ionic compounds. I believe in the one you mentioned it's C, O, then Os.
by Zaynab Hashm 2I
Mon Sep 30, 2019 8:37 pm
Forum: SI Units, Unit Conversions
Topic: Writing Compound Formulas
Replies: 3
Views: 62

Re: Writing Compound Formulas

For this certain example you mentioned (Magnesium Sulfate Heptahydrate), you need to at least know the symbols for certain elements from the periodic table. Magnesium is Mg, so you write that down first as it comes first in the name, then you add sulfate which is SO4(2-), for this one you should rec...
by Zaynab Hashm 2I
Mon Sep 30, 2019 8:25 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Mole ratios
Replies: 4
Views: 80

Re: Mole ratios

If you're asking about the coefficients you get from balancing equations, I believe these are just ratios used to determine relations between reactants and products. They aren't in fact the actual amount of how much you have of each reactant or product.
by Zaynab Hashm 2I
Mon Sep 30, 2019 8:14 pm
Forum: Molarity, Solutions, Dilutions
Topic: Molarity Audio-Visual Focus-Topics Question 23
Replies: 3
Views: 46

Re: Molarity Audio-Visual Focus-Topics Question 23

You have to use the formula M1V1=M2V2. You already have both volumes, but you need to find the molarity of KMnO4. To do so, divide the mass (5 g) by the molar mass (39.10+54.94+(16x4)=158.04 g/mol), and you will get the number of moles = 0.0316 mol. After that use the moles to divide by the volume i...
by Zaynab Hashm 2I
Mon Sep 30, 2019 7:06 pm
Forum: Molarity, Solutions, Dilutions
Topic: CuSO4 vs CuSO4 [tex]\cdot[/tex] 5H2O
Replies: 4
Views: 76

Re: CuSO4 vs CuSO4 [tex]\cdot[/tex] 5H2O

Both CuSO4 and CuSO4.5H2O are forms of the the same chemical compound; Copper (II) Sulfate. However the difference between them is that CuSO4 alone is anhydrous (containing no water), whereas CuSO4.5H2O is hydrated (surrounded by water molecules). In other words, you get CuSO4.5H2O when you put CuSO...

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