Search found 32 matches

by Kevin To 1B
Sun Jul 28, 2019 5:26 pm
Forum: Ionic & Covalent Bonds
Topic: Back and Fourth Arrows
Replies: 3
Views: 87

Re: Back and Fourth Arrows

Such arrows are to represent a certain chemical equation that can go forward or reverse. Generally, these arrows appear in chemical equations that deal with equilibrium, including acid-base equilibria. The direction of the reaction would depend on the quantity of reactants vs products, as determined...
by Kevin To 1B
Sun Jul 28, 2019 10:50 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Geometry vs molecular shape
Replies: 5
Views: 78

Re: Geometry vs molecular shape

Geometry refers to the arrangement of elections, including both bond and lone pair electrons. On the other hand, shape only refers to the bond electrons. For example, NH 3 (ammonia) has 4 regions of electron density (1 lone pair and 3 [single] bonds [to the hydrogens]). The geometry of ammonia would...
by Kevin To 1B
Sat Jul 27, 2019 10:09 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 6th edition ch. 4
Replies: 1
Views: 86

Re: 6th edition ch. 4

To figure out the quantity of sigma or pi bonds, first undertand that: - Single bond: 1 sigma bond - Double bond: 1 sigma bond and 1 pi bond - Triple bond: 1 sigma bond and 2 pi bonds Knowing this, first draw out the lewis structure. Then use the information above to find the quanty of sigma and pi ...
by Kevin To 1B
Sat Jul 27, 2019 10:06 pm
Forum: Conjugate Acids & Bases
Topic: J. 19 6th edition
Replies: 1
Views: 90

Re: J. 19 6th edition

What you do is simply take the acidic oxides and react it with water to obtain their respective acids. The question asks for 1 mol of each reactant so what you would do for (a) is have 1 mole of CO 2 react with 1 mole H 2 O to obtain carbonic acid (H 2 CO 3 ). For (b), same procedure but use SO 3 in...
by Kevin To 1B
Sat Jul 27, 2019 6:13 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Strong acids
Replies: 1
Views: 91

Re: Strong acids

HAt is known as hydrogen astatide or hydoastatic acid. Idealy, it would be stronger than HI due to the trend of acid strength. However, HAt readily decomposes and At has a short-lived half life.
by Kevin To 1B
Thu Jul 25, 2019 6:06 pm
Forum: Bronsted Acids & Bases
Topic: finding initial molarity hw 12.25
Replies: 2
Views: 122

Re: finding initial molarity hw 12.25

First, let's realize that Ba(OH) 2 dissociates into Ba 2+ and (OH) - . As a chemical equation, we can write: Ba(OH) 2 (s) → Ba 2+ (aq) + 2(OH) - (aq) (a) Initial Molarity of Ba(OH) 2 We just use stoichiometry to calculate the initial molarity. We are given 0.43 g Ba(OH) 2 in 0.100 L of solution. Con...
by Kevin To 1B
Wed Jul 24, 2019 6:49 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: edta
Replies: 7
Views: 250

Re: edta

Since EDTA is hexadentate, it can attach 6 times to the metal. Fun fact, this property allows it to displace molecules, hence why it is used in many buffers (e.g. SDS-PAGE).
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by Kevin To 1B
Wed Jul 24, 2019 6:44 pm
Forum: Bronsted Acids & Bases
Topic: Fundamentals J.7(c) (6th ed)
Replies: 2
Views: 164

Fundamentals J.7(c) (6th ed)

Question J.7(c) asks to select an acid and a base for the neutralization reaction that results in the formation of Ca(CN)2. I understand that HCN(aq) is the acid and Ca(OH)2 is the base. I am wondering if the Lewis base, CaO (calcium oxide) would also be an appropriate answer for a base?
by Kevin To 1B
Sun Jul 21, 2019 2:42 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Hybridization
Replies: 2
Views: 114

Re: Hybridization

Since Be forms 2 bonds (2 sigma bonds) with Cl, BeCl2 has a hybridization of sp.
by Kevin To 1B
Fri Jul 19, 2019 2:41 pm
Forum: Ionic & Covalent Bonds
Topic: Notation of electron configurations of ions
Replies: 5
Views: 155

Re: Notation of electron configurations of ions

The 3d10 orbital has to be included in the electron configuration.
by Kevin To 1B
Fri Jul 19, 2019 2:39 pm
Forum: Lewis Structures
Topic: Central Atom
Replies: 3
Views: 122

Re: Central Atom

The central atom is essentially required to form at least one bond, other than H and F. Nonetheless, some chemicals do have other halogen atoms as the central atom, such as perchlorate (ClO4-), depending on the conditions.
by Kevin To 1B
Tue Jul 16, 2019 7:07 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Energy State
Replies: 2
Views: 141

Re: Energy State

An electron configuration at the ground state would have an equivalent # of electrons in the element, for the ground state by definition is the lowest energy level an electron can occupy. An electron configuration at an excited state would have additional electrons due to added energy.
by Kevin To 1B
Tue Jul 16, 2019 7:03 pm
Forum: Ionic & Covalent Bonds
Topic: 3.51 6th Ed.
Replies: 2
Views: 156

Re: 3.51 6th Ed.

I think that first, the lewis structure with the least formal charge is the most stable, hence the structure with oxygen as the central atom. Moreover, this acid dissociates into H+ and OCl-, which means demonstrates that oxygen, once again, is the central atom.
by Kevin To 1B
Fri Jul 12, 2019 11:01 pm
Forum: Ionic & Covalent Bonds
Topic: Friday's Lecture July 12, 2019
Replies: 2
Views: 139

Re: Friday's Lecture July 12, 2019

According to Dr. Lavelle, Boron is one of those exceptions to the octet rule. It is important to note that Boron often only makes three covalent bonds.
by Kevin To 1B
Fri Jul 12, 2019 1:02 am
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge
Replies: 4
Views: 142

Re: Formal Charge

A formal charge is a comparison of electrons "owned" by an atom in a Lewis structure versus the number of electrons possessed by the same atom in its unbound, free atomic state. With formal charge, the molecule's net charge could be determined.
by Kevin To 1B
Wed Jul 10, 2019 8:23 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ground State vs. Excited State
Replies: 2
Views: 141

Re: Ground State vs. Excited State

The ground state of an element is has the electron configuration in order, while an electron in the excited state is not. With enough excitation, the electrons in the excited state could be anywhere and out of order.
by Kevin To 1B
Wed Jul 10, 2019 8:19 am
Forum: Photoelectric Effect
Topic: Which Equation Do I Use?
Replies: 4
Views: 232

Re: Which Equation Do I Use?

The overall equation for the photoelectric effect is:
E(photon) = Work function + KE

E(photon) and the work function could be calculated for Energy using E=hv. (v here is nu or frequency) KE, however, must be solved using its own respective equation, 1/2*m*v2. (v here is velocity)
by Kevin To 1B
Mon Jul 08, 2019 7:05 pm
Forum: Quantum Numbers and The H-Atom
Topic: Numbers
Replies: 2
Views: 135

Re: Numbers

To add on, here are the guidelines for the values each quantum number can have, given n (principal quantum number):
> l: 0, 1, 2, ... , n-1
> ml: l, l-1, ... , -l
> ms: +1/2 or -1/2
by Kevin To 1B
Mon Jul 08, 2019 6:59 pm
Forum: Properties of Light
Topic: Pre/Post assessment question. [ENDORSED]
Replies: 2
Views: 203

Re: Pre/Post assessment question. [ENDORSED]

When two peaks or two troughs of two different waves interact simultaneously, this is an example of constructive interference, which amplifies the resulting wave. When a peak of one wave interacts with a trough of another wave, the resulting wave becomes smaller. This is known as destructive interfe...
by Kevin To 1B
Mon Jul 08, 2019 6:54 pm
Forum: Photoelectric Effect
Topic: Converting electron volts? [ENDORSED]
Replies: 2
Views: 129

Re: Converting electron volts? [ENDORSED]

If you take a look the "Constants and Equations" sheet (on Dr. Lavelle's Class Website and also on the front cover of each Test/Exam),
1 eV = 1.602 × 10-19 J.
by Kevin To 1B
Fri Jul 05, 2019 10:13 pm
Forum: Photoelectric Effect
Topic: Photoelectric effect answer
Replies: 2
Views: 143

Re: Photoelectric effect answer

Wavelength is usually measured in meters, for that is its SI unit. I think it's safe to say that you can use (m) as your units as long as your answer is in the appropriate scientific notation if it is smaller or bigger than a meter.
by Kevin To 1B
Fri Jul 05, 2019 10:10 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2A.5 part c
Replies: 2
Views: 122

Re: 2A.5 part c

So for Galium, the ground state electron configuration is [Ar] 3d 10 4s 2 4p 1 . The ion, Ga 3+ has a postive 3 charge, meaning that 3 electrons are lost. Therefore, the three electrons that will be removed are the one 4p electron and the two 4s electrons, since they are in the outermost shell. The ...
by Kevin To 1B
Thu Jul 04, 2019 10:58 pm
Forum: Properties of Light
Topic: Balmer series and Lyman series
Replies: 2
Views: 128

Re: Balmer series and Lyman series

To add on, the Lyman series would correspond to UV light, while the Balmer series would correspond to visible light.
by Kevin To 1B
Mon Jul 01, 2019 10:02 pm
Forum: Limiting Reactant Calculations
Topic: Are these important? [ENDORSED]
Replies: 3
Views: 183

Re: Are these important? [ENDORSED]

The conditions "1 atm and 25 degrees C" just indicate that the reaction is occuring at standard ambient temperature and pressure, or SATP.
by Kevin To 1B
Mon Jul 01, 2019 1:40 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: c or m as concentration
Replies: 2
Views: 108

Re: c or m as concentration

In the textbook, molar concentration is denoted as "c" (which I assume is 'concentration'). Molar concentration is the same thing as Molarity, which is denoted as "M". Generally, we would use M as units to indicate the molarity (e.g. 5 M) but I think that in equations, the variab...
by Kevin To 1B
Mon Jul 01, 2019 1:34 pm
Forum: Limiting Reactant Calculations
Topic: Dividing by the Stoichiometric Coefficient
Replies: 2
Views: 126

Re: Dividing by the Stoichiometric Coefficient

After you have the moles of a substance, you would divide by the mole ratio to convert between moles of one reactant to moles of one product. Using the coefficients for the values of the mole ratio, the "units" at the end of the conversion would be "moles of [whatever substance you're...
by Kevin To 1B
Fri Jun 28, 2019 2:26 pm
Forum: Properties of Light
Topic: limiting reagents
Replies: 4
Views: 257

Re: limiting reagents

Another method of determining the limiting reagent is to convert the mass of the reactants into moles using the molar mass. Choose one of the products and multiply the moles of reactants calculated by the mole ratio of [mole of that one product]/[mole of the respective reactant]. Whichever reactant ...
by Kevin To 1B
Fri Jun 28, 2019 2:18 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Theoretical/Actual Yield
Replies: 6
Views: 173

Re: Theoretical/Actual Yield

When calculating percent yield in a lab, the product obtained from a reaction/experiment will generally be weighed and its mass is recorded. Therefore, knowing that actual yield is in a unit of mass, theoretical yield has to also be in the same unit of mass in order to calculate percent yield.
by Kevin To 1B
Fri Jun 28, 2019 2:12 pm
Forum: Significant Figures
Topic: Determining sig figs
Replies: 10
Views: 375

Re: Determining sig figs

The reason why 100 only has one significant figure is due to the fact that zeros that only hold places are not considered to be significant.
by Kevin To 1B
Fri Jun 28, 2019 2:06 pm
Forum: SI Units, Unit Conversions
Topic: Calculating amount of molecules
Replies: 3
Views: 172

Re: Calculating amount of molecules

Blanca Cervantes wrote:Dividing mass sample by molar mass:
(2.3 x 10^5)/ 60.05526= 3829.80


That right there is 3.8 x10^3 moles, as indicated by your answer. Is there any chance the question asks for the amount in moles instead of molecules? (as a typo)
by Kevin To 1B
Fri Jun 28, 2019 1:57 pm
Forum: Balancing Chemical Reactions
Topic: Combustion Equation
Replies: 18
Views: 676

Re: Combustion Equation

generally the equation is CxHyOz + O2= CO2 + H20 Combustion reactions are most of the time with hydrocarbons and according to the definition, hydrocarbons at their basic form do not have oxygen. Therefore, the basic equation of a combustion reaction with hydrocarbons should just be CxHy + O2 → CO2 ...
by Kevin To 1B
Mon Jun 24, 2019 7:29 pm
Forum: Limiting Reactant Calculations
Topic: Lim Reactant Module: question 20 [ENDORSED]
Replies: 2
Views: 168

Re: Lim Reactant Module: question 20 [ENDORSED]

You are given 1 kg of CaCO3, which is equivalent to 1000g CaCO3. Use the molar mass of CaCO3 to convert the 1000g into number of moles CaCO3. Then, knowing that the mole ratio of CaCO3:CO2 is 1:1, you can use this to convert moles of CaCO3 to moles of CO2. Also, the conditions "1 atm and 25 deg...

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