Search found 102 matches

by RRahimtoola1I
Thu Mar 12, 2020 11:50 am
Forum: Balancing Redox Reactions
Topic: Oxygen
Replies: 5
Views: 33

Re: Oxygen

O2 and O3 has an oxidation number of 0, but O in any other compound or molecule has an oxidation number of -2.
by RRahimtoola1I
Thu Mar 12, 2020 11:47 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: How to determine order
Replies: 3
Views: 39

Re: How to determine order

You can use the experimental method when they give you a table of concentrations of reactants for different experiments and their rates to cancel and find the order. You can use graphs if given: - first order should be a straight negative slope plotted over ln[A] vs. time - second should be a straig...
by RRahimtoola1I
Thu Mar 12, 2020 11:44 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Pre-Equilibrium
Replies: 3
Views: 30

Re: Pre-Equilibrium

You use the pre-equilibrium method when the earlier step is the fast step and the later step is a slow step. You can then think of the fast step as being almost at equilibrium and use that to solve.
by RRahimtoola1I
Thu Mar 12, 2020 11:41 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: 7b.3c - where did the ln come from?
Replies: 6
Views: 37

Re: 7b.3c - where did the ln come from?

If you use the equation ln[A] = -kt + ln[A]0 you can see this will happen. You should be subtracting over the ln[A]0 before dividing and with laws of natural logs, if you subtract two logs you are basically taking the natural log of the two divided so that's why you are dividing 0.085/0.153 and then...
by RRahimtoola1I
Thu Mar 12, 2020 11:38 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: 7A.11) 700K?
Replies: 6
Views: 64

Re: 7A.11) 700K?

Yes you ignore it. I got the answer without using it.
by RRahimtoola1I
Thu Mar 12, 2020 11:35 am
Forum: First Order Reactions
Topic: question 7b.5
Replies: 3
Views: 25

Re: question 7b.5

Make sure to convert the hours into seconds so the units match up correctly!
by RRahimtoola1I
Thu Mar 12, 2020 11:30 am
Forum: General Rate Laws
Topic: 7A.17
Replies: 5
Views: 69

Re: 7A.17

You just need two experiments that have the same concentration for both experiments so you can cancel them to find the order of the one with different concentrations.
by RRahimtoola1I
Thu Mar 12, 2020 11:26 am
Forum: General Rate Laws
Topic: Rate Determining Step
Replies: 5
Views: 27

Re: Rate Determining Step

The rate determining step is the slow step. You can think of it this way. If two runners are tied together, one who is a track star and one who has never run before, even if the track star can outrun the slower runner, they are prevented because they are tied together. They can only move as fast as ...
by RRahimtoola1I
Sat Mar 07, 2020 11:25 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 7D1
Replies: 4
Views: 65

Re: 7D1

What equation are they using in this problem?
by RRahimtoola1I
Sat Mar 07, 2020 11:24 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Where do we find the values for A?
Replies: 5
Views: 74

Where do we find the values for A?

Are the values for A given to us somewhere or is there a way to calculate them?
by RRahimtoola1I
Sat Mar 07, 2020 10:25 pm
Forum: First Order Reactions
Topic: how to know actual order
Replies: 4
Views: 73

how to know actual order

In 7B.3 it tells us that the reactions are all first order but in part c the reaction is 2A > B + C which I thought would be a second order reaction. Do we not use the coefficients to find the order of the reaction?
by RRahimtoola1I
Sat Mar 07, 2020 10:12 pm
Forum: Second Order Reactions
Topic: 7B.3
Replies: 5
Views: 76

Re: 7B.3

You write out the rate law for the first-order reaction, then you find that [A] decreased by .068M over 115 seconds as the rate, then you can plug in all the information you know, leaving the k constant as the only unknown since you know [A], the rate, and that the reaction is first-order, and solv...
by RRahimtoola1I
Sat Mar 07, 2020 9:48 pm
Forum: First Order Reactions
Topic: 7B.9
Replies: 1
Views: 40

7B.9

How do you do this problem or other problems similar to this when they give you only the initial concentration of the reactant and then a later concentration of a product? For the first-order reaction A > 3B + C, when initial concentration of A = 0.015 mol/L, the concentration of B increases to 0.01...
by RRahimtoola1I
Sat Mar 07, 2020 9:25 pm
Forum: Second Order Reactions
Topic: 7B.3
Replies: 5
Views: 76

7B.3

How do you do part c of this question.( i.e. how do you find concentration of A) Determine the rate constant for each of the following first- order reactions, in each case expressed for the rate of loss of A: c) 2A > B + C [A]0 = 0.153 mol/L after 115s the concentration of B rises to 0.034 mol/L
by RRahimtoola1I
Thu Mar 05, 2020 9:12 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6N.23
Replies: 1
Views: 26

6N.23

How do we know what can be used for electrodes based on the other metals given. (a) Suggest two metals that could be used for the cathodic protection of a titanium pipeline. (b) What factors other than relative positions in the electrochemical series need to be consid- ered in practice? (c) Often co...
by RRahimtoola1I
Sat Feb 29, 2020 7:56 pm
Forum: Balancing Redox Reactions
Topic: When to add H+ or H20
Replies: 19
Views: 169

Re: When to add H+ or H20

This is how you balance for both: 1. determine the oxidation and reduction half reactions. 2. Balance both half reactions: a) Balance elements other than H or O b) Balance O elements by adding H2O molecules to match the number of O molecules you have. c) Balance H elements by adding H+ (aq) FOR BASE...
by RRahimtoola1I
Sat Feb 29, 2020 7:50 pm
Forum: Balancing Redox Reactions
Topic: Cell Diagrams
Replies: 14
Views: 84

Re: Cell Diagrams

It does matter.
The anode is always on the left and the cathode is on the right with a salt bridge symbolized by "||" in the middle.
by RRahimtoola1I
Sat Feb 29, 2020 7:48 pm
Forum: Balancing Redox Reactions
Topic: Acidic and Basic solutions
Replies: 11
Views: 80

Re: Acidic and Basic solutions

YES! They are different. Here's what my TA said for the difference: 1. determine the oxidation and reduction half reactions. 2. Balance both half reactions: a) Balance elements other than H or O b) Balance O elements by adding H2O molecules to match the number of O molecules you have. c) Balance H e...
by RRahimtoola1I
Sat Feb 29, 2020 7:47 pm
Forum: Balancing Redox Reactions
Topic: Difference between balancing Basic and Acidic
Replies: 3
Views: 32

Re: Difference between balancing Basic and Acidic

This is how you balance for both: 1. determine the oxidation and reduction half reactions. 2. Balance both half reactions: a) Balance elements other than H or O b) Balance O elements by adding H2O molecules to match the number of O molecules you have. c) Balance H elements by adding H+ (aq) FOR BASE...
by RRahimtoola1I
Sat Feb 29, 2020 7:43 pm
Forum: Balancing Redox Reactions
Topic: Oxidizing/reducing agent
Replies: 18
Views: 151

Re: Oxidizing/reducing agent

An oxidizing agent is one that oxidizes and thereby gets reduced.

A reducing agent is one that reduces and thereby gets oxidized.
by RRahimtoola1I
Tue Feb 25, 2020 11:46 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cathode vs Anode
Replies: 6
Views: 50

Re: Cathode vs Anode

you can also use "AN OIL RIG CAT" which means oxidation is loss of electrons at the anode and reduction is gain of electrons at the cathode.
by RRahimtoola1I
Tue Feb 25, 2020 11:44 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Standard Cell Potential
Replies: 4
Views: 41

Re: Standard Cell Potential

E naught is when the cell is at 1M, 1atm, and 25*C. E naught is standard cell potential.
by RRahimtoola1I
Tue Feb 25, 2020 11:43 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 4
Views: 50

Re: Cell Diagrams

anode on the left
cathode on the right
separate phases by "|" going from solids on the outside to gases on the inside
by RRahimtoola1I
Tue Feb 25, 2020 11:41 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: How to Order Cell Diagrams
Replies: 2
Views: 25

Re: How to Order Cell Diagrams

Anode is on the left, cathode is on the right separated by || (Salt bridge).

You separate phases by "|" putting solids on the outside and working in towards gases.
by RRahimtoola1I
Tue Feb 25, 2020 11:40 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: what is value of E°?
Replies: 2
Views: 24

Re: what is value of E°?

You just plug in the standard cell potential they give you into E* = E*(cath) -E*(an). So it would be the way you did it first if you are not changing any of the signs given in the table.
by RRahimtoola1I
Tue Feb 25, 2020 11:37 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6M.7, standard potential
Replies: 1
Views: 40

Re: 6M.7, standard potential

I'm not sure but you can also look at electronegativity of an atom. The lower the electronegativity the stronger reducing agent it will be because it will be losing electrons (oxidation).
by RRahimtoola1I
Tue Feb 25, 2020 11:27 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Platinum on one side of galvanic diagram
Replies: 3
Views: 37

Platinum on one side of galvanic diagram

Why is Pt(s) only added on one side of a galvanic diagram sometimes. For example, in 6M.5 part a, the cell diagram in the solution manual is:

Hg(l) | Hg2^2+(aq) || NO^3-(aq), H^+(aq) | NO(s) | Pt(s)
by RRahimtoola1I
Tue Feb 25, 2020 11:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7
Replies: 1
Views: 29

6L.7

How do you do this problem with the equilibriums?
by RRahimtoola1I
Tue Feb 25, 2020 11:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Platinum
Replies: 1
Views: 19

Platinum

In what case do you add platinum and when do you not when drawing cell diagrams?
by RRahimtoola1I
Mon Feb 24, 2020 3:44 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic/Voltaic Cells
Replies: 4
Views: 39

Re: Galvanic/Voltaic Cells

A galvanic cell requires no input of energy because the reactions are spontaneous and favorable. Electrons and cations travel from the anode to the cathode producing energy. A galvanic cell, overall, turns chemical energy into electrical energy.
by RRahimtoola1I
Mon Feb 24, 2020 3:38 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams
Replies: 9
Views: 55

Re: Cell Diagrams

The | separates phases (Solid, aqueous, gas) and the || means a salt bridge and can also separate the anode and cathode.
by RRahimtoola1I
Mon Feb 24, 2020 3:32 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Flow of Galvanic cell
Replies: 3
Views: 31

Re: Flow of Galvanic cell

The cations move through the salt bridge or the porous disk because of the reasons ^^^. They are attracted to the negative cathode.
by RRahimtoola1I
Mon Feb 24, 2020 12:02 am
Forum: Balancing Redox Reactions
Topic: Acids and Bases
Replies: 4
Views: 52

Re: Acids and Bases

You add the H2O to balance out the oxygens and then add H+ to balance out the hydrogens and then the same amount of OH- as H+ you added. Then you combine them to form water.
by RRahimtoola1I
Sun Feb 23, 2020 11:30 pm
Forum: Balancing Redox Reactions
Topic: Test 2
Replies: 9
Views: 82

Re: Test 2

The test will be in week 9 during discussion.
by RRahimtoola1I
Sun Feb 23, 2020 11:28 pm
Forum: Balancing Redox Reactions
Topic: Acidic and Basic
Replies: 3
Views: 45

Re: Acidic and Basic

I would also like to know how to differentiate between acidic and basic reactions.
by RRahimtoola1I
Tue Feb 11, 2020 2:25 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4D.3
Replies: 1
Views: 33

4D.3

The reaction of 1.40 g of carbon monoxide with excess water vapor to produce carbon dioxide and hydrogen gases in a bomb calorimeter causes the temperature of the calorimeter assembly to rise from 22.113 8C to 22.799 8C. The calorimeter assembly is known to have a total heat capacity (calorimeter co...
by RRahimtoola1I
Tue Feb 11, 2020 2:10 pm
Forum: Phase Changes & Related Calculations
Topic: 4C.15
Replies: 1
Views: 45

4C.15

Can someone explain how to differentiate between which heating curve is correct?
by RRahimtoola1I
Tue Feb 11, 2020 1:59 pm
Forum: Phase Changes & Related Calculations
Topic: 4.C.13
Replies: 1
Views: 40

4.C.13

How do you break this problem down to solve for the ice melting and the water heating. The solution manual is not making sense? An ice cube of mass 50.0 g at 0.0 8C is added to a glass containing 400.0 g of water at 45.0 8C. What is the final tempera- ture of the system (see Tables 4A.2 and 4C.1)? A...
by RRahimtoola1I
Tue Feb 11, 2020 1:49 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 4C.3
Replies: 1
Views: 37

4C.3

Is the correct answer the one in the back of the book? I keep getting 342.8K for my final temperature. Calculate the final temperature and the change in enthalpy when 765 J of energy is transferred as heat to 0.820 mol Kr(g) at 298 K and 1.00 atm (a) at constant pressure; (b) at constant vol- ume. T...
by RRahimtoola1I
Tue Feb 11, 2020 1:47 pm
Forum: Phase Changes & Related Calculations
Topic: 4C.7
Replies: 1
Views: 26

4C.7

How do you do this problem? I was using q = nH and q = mH but I am not getting the correct answer. "(a)Atitsboilingpoint,thevaporizationof0.579molCH4(l) requires 4.76 kJ of heat. What is the enthalpy of vaporization of methane? (b) An electric heater was immersed in a flask of boiling ethanol, ...
by RRahimtoola1I
Wed Jan 29, 2020 10:29 pm
Forum: Phase Changes & Related Calculations
Topic: 4A.3
Replies: 3
Views: 50

4A.3

Can someone please explain this problem. The solution manual is using 101.325J as a conversion but I'm not sure where they are getting it from. Other than that, I still don't understand the problem.
by RRahimtoola1I
Sat Jan 25, 2020 12:45 pm
Forum: Ideal Gases
Topic: Topics on Test 1
Replies: 37
Views: 321

Re: Topics on Test 1

Outline 1 and 2 except for 6E.
by RRahimtoola1I
Sat Jan 25, 2020 12:31 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: kA and kB
Replies: 3
Views: 76

Re: kA and kB

Yes that's right! Also remember that it's not like pH where the higher the number the stronger the base and the lower the number the stronger the acid. For both acids and bases, the lower the pKa or pKb the stronger the acid or base.
by RRahimtoola1I
Sat Jan 25, 2020 12:29 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Ka*Kb=Kw
Replies: 5
Views: 95

Re: Ka*Kb=Kw

Make sure you are using -14 not -4!
by RRahimtoola1I
Sat Jan 25, 2020 12:07 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Value of X
Replies: 7
Views: 55

Re: Value of X

Set up a K expression using an ICE table and solve for x setting the expression equal to Ka, Kb, or Kc.
by RRahimtoola1I
Sat Jan 25, 2020 12:04 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: biological examples
Replies: 7
Views: 87

biological examples

The following is stated on Outline 1 as things we have to know...

"Biological examples. For example: ATP hydrolysis; osmotic pressure"

Can anyone tell me what we have to know about it because I don't recall going over this?
by RRahimtoola1I
Sat Jan 25, 2020 12:01 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Pressure
Replies: 3
Views: 31

Pressure

In high school chem I learned that the way the reaction shifts based on an increase or decrease of pressure depends on the amount of moles on each side of the reaction. I know Prof. Lavelle said there was another way that was better to determine which way the reaction shifts, but I don't remember it...
by RRahimtoola1I
Sat Jan 25, 2020 11:55 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Partial Pressure vs. Concentration
Replies: 5
Views: 35

Partial Pressure vs. Concentration

It says on outline 1 that we have to know when to differentiate between using partial pressure and concentration for the equilibrium constant. How do we know which one to use when there are only gases but they don't give any other information like concentration or partial pressure?
by RRahimtoola1I
Sat Jan 25, 2020 11:47 am
Forum: Ideal Gases
Topic: R Constant
Replies: 26
Views: 245

Re: R Constant

Here are the different gas constants. It depends on the units you are using in the equation. For PV=nRT you would usually use the 0.082.
by RRahimtoola1I
Wed Jan 22, 2020 10:21 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 5I 25
Replies: 2
Views: 36

5I 25

Will we have to know how to factor a complicated problem like this one where there is a quadratic over a quadratic for tests?
by RRahimtoola1I
Sat Jan 11, 2020 1:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: liquids and aqueous solutions
Replies: 4
Views: 26

Re: liquids and aqueous solutions

Aqueous solutions have measurable and changeable concentrations. Liquids don't have significantly changeable concentrations and solids don't have measurable concentrations.
by RRahimtoola1I
Sat Jan 11, 2020 1:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Change in k
Replies: 11
Views: 108

Re: Change in k

This is true because of LeChatelier's principle that a reaction will try to minimize change to equilibrium. If more reactants are added the reaction shifts towards the products producing more product in the same ration that K was initially.
by RRahimtoola1I
Sat Jan 11, 2020 1:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Table Calculations
Replies: 4
Views: 30

Re: ICE Table Calculations

Basically, because we don't have access to a graphing calculator, anything that you can't do without it like a cubic function for example can be simplified.
by RRahimtoola1I
Sat Jan 11, 2020 1:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Assuming +/- x is Negligible
Replies: 4
Views: 46

Re: Assuming +/- x is Negligible

I'm pretty sure you are correct that if K < 10-5 you can use approximation.
by RRahimtoola1I
Thu Jan 09, 2020 11:46 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G3
Replies: 8
Views: 51

Re: 5G3

I believe only gases are included when finding equilibrium constants. Also, can someone explain how to ask a question on Chem Community? I cannot figure out how to. Thanks You have to go to a certain topic and then click on new topic in the top left corner. Name the subject something that people ca...
by RRahimtoola1I
Thu Jan 09, 2020 11:13 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.9
Replies: 4
Views: 55

5G.9

Can someone explain how to understand this question? "A sample of ozone, O3, amounting to 0.10 mol, is placed in a sealed container of volume 1.0 L and the reaction 2 O3(g) S 3 O2(g) is allowed to reach equilibrium. Then 0.50 mol O3 is placed in a second container of volume 1.0 L at the same te...
by RRahimtoola1I
Sun Dec 01, 2019 1:14 pm
Forum: Hybridization
Topic: drawing out hybridization diagrams
Replies: 1
Views: 38

Re: drawing out hybridization diagrams

It's a possibility because we went over it in the notes, but I also don't think it would need to be detailed because it never showed up on the HW and the exams usually follow the format of the HW.
by RRahimtoola1I
Sun Dec 01, 2019 12:50 pm
Forum: Hybridization
Topic: Focus 2.45
Replies: 3
Views: 53

Re: Focus 2.45

Also why are there two hybridizations written for each bond even though they are the exact same thing? And why is the pi bond hybridization different from the sigma bond hybridization?
by RRahimtoola1I
Sat Nov 30, 2019 2:18 pm
Forum: Hybridization
Topic: Atomic Orbital Promotion
Replies: 1
Views: 53

Atomic Orbital Promotion

Can someone please explain the transition between a normal atomic orbital and the hybrid orbital? I mean when we write the electron configuration with the arrows and how it changes in hybrids.

Can someone also explain it in terms of ethene because the notes I took are not making sense to me?
by RRahimtoola1I
Sat Nov 30, 2019 2:11 pm
Forum: Hybridization
Topic: Counting Charge Clouds
Replies: 2
Views: 31

Counting Charge Clouds

When counting charge clouds does it matter whether it's a single, double, or triple bond or does it always count as 1 charge cloud?
by RRahimtoola1I
Sat Nov 30, 2019 2:10 pm
Forum: Hybridization
Topic: Hybridization
Replies: 7
Views: 84

Hybridization

Just a clarification because I thought hybridization would be more complicated. Do we just have to draw the Lewis structure, count the amount of charge clouds, and memorize the hybrid orbitals for each amount of charge cloud and write it down?

Does it get more complicated than this for this course?
by RRahimtoola1I
Sun Nov 24, 2019 9:03 pm
Forum: Sigma & Pi Bonds
Topic: sigma and pi bonds
Replies: 19
Views: 336

Re: sigma and pi bonds

A single bond is a sigma bond and every other bond after that is a pi bond. For example, in a double bond, there's one sigma and one pi bond and in a triple bond there's one sigma and two pi bonds.
by RRahimtoola1I
Thu Nov 21, 2019 9:38 am
Forum: Ionic & Covalent Bonds
Topic: Hydrogen Bond Sites
Replies: 5
Views: 167

Hydrogen Bond Sites

What is considered a hydrogen bond site on a molecule?
by RRahimtoola1I
Wed Nov 20, 2019 5:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar vs. Nonpolar
Replies: 6
Views: 97

Polar vs. Nonpolar

I understand that CH2Cl2 is polar because a tetrahedral shape isn't completely symmetrical. However if a shape is symmetrical like a square planar would it be considered nonpolar? For example if it was a square planar with two Cl and two H atoms around a central atom, would it be considered non polar?
by RRahimtoola1I
Wed Nov 20, 2019 5:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.25
Replies: 3
Views: 34

Re: 2E.25

Could you say that it would only be nonpolar if all the atoms around the central atom were the same?
by RRahimtoola1I
Wed Nov 20, 2019 4:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.21
Replies: 1
Views: 23

2E.21

How do you do part a from 2E.21? It asks to draw the Lewis structure and give approximate bond angles of C2H4. Maybe I'm drawing it wrong but what is the central atom? I have the carbons bonded with two hydrogens bonded to each.
by RRahimtoola1I
Sat Nov 16, 2019 3:26 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar vs. Nonpolar
Replies: 12
Views: 135

Re: Polar vs. Nonpolar

It's better to determine whether a molecule is polar or non polar based on VSPER rather than Lewis Structure because it isn't always clear with the Lewis Structure. For H2O for example it seems like it would be non polar because it's symmetrical but the VSPER structure shows it's polar because of th...
by RRahimtoola1I
Sat Nov 16, 2019 2:51 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Trigonal Pyramid vs Trigonal Planar
Replies: 6
Views: 52

Re: Trigonal Pyramid vs Trigonal Planar

They are two completely different shapes. Trigonal planar has no lone pairs and 3 bonded pairs while trigonal pyramidal has 1 lone pair and 3 bonded pairs.
by RRahimtoola1I
Sat Nov 16, 2019 2:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Drawing Molecular Structures
Replies: 8
Views: 58

Re: Drawing Molecular Structures

Will we need to know how to draw the molecular structures in this way for the test?
by RRahimtoola1I
Sat Nov 16, 2019 2:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Inter-molecular Electron Repulsion
Replies: 6
Views: 45

Re: Inter-molecular Electron Repulsion

What is an example of a lone-bonding pair?
by RRahimtoola1I
Sat Nov 16, 2019 2:35 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Symmetry and Polarity
Replies: 13
Views: 114

Re: Symmetry and Polarity

Are the molecules that are considered polar the ones with no lone electron pairs? So only linear, tetrahedral, trigonal planar, etc.?
by RRahimtoola1I
Sat Nov 16, 2019 2:20 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSPER Formula for Compounds with No Lone Pairs
Replies: 4
Views: 37

VSPER Formula for Compounds with No Lone Pairs

What would the VSPER formula for a compound with a tetrahedral shape look like?

Do we just not include "E" when writing the formula?
by RRahimtoola1I
Sat Nov 16, 2019 2:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSPER Formula
Replies: 2
Views: 33

VSPER Formula

Do we have to know how to identify molecular shapes based on just a VSPER formula or will he most likely give us a compound that we have to find the Lewis Structure of to determine the VSPER shape?
by RRahimtoola1I
Sat Nov 16, 2019 2:14 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 9
Views: 81

Re: Bond Angles

It's probably easiest to just memorize a chart with all the bond angles stated, but for the test he said we just have to be able to say that a trigonal pyramidal shape has a smaller bond angle than a tetrahedral because of the lone pair having more repulsion than the bonded pair.
by RRahimtoola1I
Wed Nov 13, 2019 7:32 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.5 b
Replies: 4
Views: 39

2E.5 b

OClO has 19 valence electrons so it's a radical. Do we count the extra electron even though it's not in a pair when determining shape?
by RRahimtoola1I
Tue Nov 05, 2019 11:28 pm
Forum: Octet Exceptions
Topic: When to use Expanded Octet?
Replies: 2
Views: 57

When to use Expanded Octet?

Are you supposed to use an expanded octet if you can make a Lewis Structure without it? For example, in ClO would I give Cl 9 electrons by making a double bond or leave it with 7 with a single bond even though the single bond gives Cl a -1 formal charge?
by RRahimtoola1I
Sun Nov 03, 2019 5:18 pm
Forum: Lewis Structures
Topic: line structure
Replies: 1
Views: 23

Re: line structure

Line structures omit lone electron pairs and just show bonds while Lewis structures have both.
by RRahimtoola1I
Sun Nov 03, 2019 5:17 pm
Forum: Lewis Structures
Topic: More stable structures
Replies: 2
Views: 36

Re: More stable structures

I'm pretty sure the stability of a Lewis structure is based off of formal charge and which atoms have what formal charges. Typically, the more electronegative atoms rather have a negative formal charge than less electronegative atoms.
by RRahimtoola1I
Sun Nov 03, 2019 2:59 pm
Forum: Octet Exceptions
Topic: Identifying Radicals
Replies: 6
Views: 72

Re: Identifying Radicals

Can someone explain this by using a Lewis structure too?

Ashley, I think they are important because they are highly reactive and exist for a short time.
by RRahimtoola1I
Sat Nov 02, 2019 9:51 pm
Forum: Ionic & Covalent Bonds
Topic: 2B.9
Replies: 1
Views: 36

2B.9

How do you know what is ionic and what isn't?

For part b and c it's obvious because there's a metal involved, but for ammonium chloride, they are all nonmetals.
by RRahimtoola1I
Sat Nov 02, 2019 6:35 pm
Forum: Lewis Structures
Topic: Formal Charge for Lewis Structures
Replies: 4
Views: 51

Formal Charge for Lewis Structures

So I went to the UA review session on Friday and they discussed using formal charge to determine the best way to draw a Lewis Structure. I've been trying to use that but it isn't working and I keep getting the wrong answer for the homework. Is there a certain time when we should or shouldn't use the...
by RRahimtoola1I
Sun Oct 27, 2019 12:16 pm
Forum: Ionic & Covalent Bonds
Topic: 2.A.17
Replies: 3
Views: 44

2.A.17

I'm confused as to how to find how many valence electrons are present for these ions. I usually just count back on the periodic table because they're all cations and then determine the amount of valence electrons for the element I land on, but I keep getting them wrong. Is there another way to do th...
by RRahimtoola1I
Sun Oct 27, 2019 12:02 pm
Forum: Ionic & Covalent Bonds
Topic: Valence Electrons 2A.1
Replies: 2
Views: 52

Valence Electrons 2A.1

"Give the number of valence electrons (including d electrons) for each of the following elements: (a) Sb; (b) Si; (c) Mn; (d) B." For part c, do you count the d electrons because the subshell is not full because for the rest you also count subshells that are full if the shell isn't full? H...
by RRahimtoola1I
Sun Oct 27, 2019 11:31 am
Forum: Properties of Light
Topic: 1.31
Replies: 4
Views: 67

1.31

How do you find the kinetic energy of the electrons emitted? "In a recent suspense film, two secret agents must penetrate a criminal's stronghold monitored by a lithium photomultiplier cell that is continually bathed in light from a laser. If the beam of light is broken, an alarm sounds. The ag...
by RRahimtoola1I
Sun Oct 27, 2019 11:21 am
Forum: Trends in The Periodic Table
Topic: HW: 1.13
Replies: 2
Views: 42

Re: HW: 1.13

Does anyone know if we could answer this question by saying that nitrogen has one electron in each orbital which has a higher stability and that fluorine has a high electron affinity because it wants an octet and doesn't want to lose an electron instead?

Do we have to mention electron repulsion?
by RRahimtoola1I
Sun Oct 27, 2019 11:16 am
Forum: Properties of Light
Topic: Homework 1.3
Replies: 2
Views: 56

Re: Homework 1.3

I used E=hc(wavelength) too but I got 753668J for my final answer. I'm confused on what we're both doing wrong. Can someone help?
by RRahimtoola1I
Sun Oct 20, 2019 11:10 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Homework 1E.7
Replies: 3
Views: 48

Re: Homework 1E.7

What rule is part C of this question violating that makes it an excited state?
by RRahimtoola1I
Sun Oct 20, 2019 10:38 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 1.E.5
Replies: 1
Views: 28

1.E.5

Can someone please explain this entire question...why each is true/false? I don't understand. "Which of the following statements are true for many-elec- tron atoms? If false, explain why. (a) The effective nuclear charge Zeffe is independent of the number of electrons present in an atom. (b) El...
by RRahimtoola1I
Wed Oct 16, 2019 2:35 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: 1B.27 Hw Help
Replies: 5
Views: 71

Re: 1B.27 Hw Help

For ∆x, I got 6.6 x 10-36m also, but the answer in the back of the book and the solution manual is 1.3 x 10-36m. Which is the correct answer?
by RRahimtoola1I
Wed Oct 16, 2019 2:21 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 1.D.23 [ENDORSED]
Replies: 2
Views: 63

1.D.23 [ENDORSED]

"How many orbitals can have the following quantum numbers in an atom:(a)n=2, l=1; (b)n=4, l=2, ml=22; (c)n=2; (d)n=3, l=2, ml=1?" For a, is the number of orbitals only dependent on the subshell (p) and the amount of orientations possible for it? For b and d, is it only 1 because the orient...
by RRahimtoola1I
Wed Oct 16, 2019 1:29 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: HW Question 1.D.13
Replies: 3
Views: 66

Re: HW Question 1.D.13

I don't understand what to use given in the problem to get the answer. I thought b was 11 because if n=6 and l=5, then shouldn't ml = -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5? Also can someone explain c and d too?
by RRahimtoola1I
Sat Oct 12, 2019 6:26 pm
Forum: DeBroglie Equation
Topic: Mass of Protons, Neutrons, Electrons, Etc.
Replies: 3
Views: 25

Mass of Protons, Neutrons, Electrons, Etc.

2 questions:

For the mass of protons, neutrons, and electrons can we just look it up online or is there a certain value the book wants us to use and where would I find these values?

For tests, will we be given the mass of these particles?
by RRahimtoola1I
Sat Oct 12, 2019 6:18 pm
Forum: Einstein Equation
Topic: 1B.15
Replies: 2
Views: 64

1B.15

"The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 3 103 km?s21. (a) What is the wavelength of the ejected electron? (b) No electrons are emitted from the surface of the metal until the frequency of the radiation reaches 2.50 3 1016 Hz. How much energy is re...
by RRahimtoola1I
Sat Oct 12, 2019 6:04 pm
Forum: Properties of Light
Topic: HW 1.A #11
Replies: 4
Views: 71

Re: HW 1.A #11

I don't understand how the answer given answers the question. Can someone please explain? Why is grouping the series related to the base energy level?
by RRahimtoola1I
Sat Oct 12, 2019 10:34 am
Forum: Properties of Light
Topic: HW 1.A #9
Replies: 3
Views: 58

Re: HW 1.A #9

Here's an electromagnetic spectrum I found for reference. A wavelength of 340 nm would be suntanning because the sun emits UV rays. A wavelength of 1m or 1x10^9 nm would be microwaving popcorn because that wavelength falls under microwave radar. A wavelength of 2.5 nm would be x-ray because of the s...
by RRahimtoola1I
Sat Oct 12, 2019 10:13 am
Forum: *Particle in a Box
Topic: Particle in a box
Replies: 2
Views: 383

Re: Particle in a box

Particles have discreet energies with only certain stable wavelengths allowed in a circular standing wave around the nucleus. Professor Lavelle was specifically talking about electrons as being the particle in a box. An electron bound to an atom is like a particle in a box in that it has to stay amo...
by RRahimtoola1I
Thu Oct 03, 2019 6:19 pm
Forum: SI Units, Unit Conversions
Topic: Advice
Replies: 3
Views: 80

Re: Advice

This can be helpful for converting between the prefixes to get to the base units on the metric system.
by RRahimtoola1I
Thu Oct 03, 2019 6:10 pm
Forum: Limiting Reactant Calculations
Topic: M.11
Replies: 3
Views: 106

M.11

"A reaction vessel contains 5.77 g of white phosphorus and 5.77 g of oxygen. The first reaction to take place is the formation of phosphorus(III) oxide, P 4 O 6 : P 4 (s) + 3 O 2 (g) > P 4 O 6 (s). If enough oxygen is present, the oxygen can react further with this oxide to produce phosphorus(V...
by RRahimtoola1I
Thu Oct 03, 2019 3:53 pm
Forum: Empirical & Molecular Formulas
Topic: Tips for Finding Which Number to Multiply a Decimal By to Get a Whole Number
Replies: 10
Views: 199

Tips for Finding Which Number to Multiply a Decimal By to Get a Whole Number

When doing empirical formula problems, after you divide by the smallest number of moles, sometimes you get a decimal which you have to convert into a whole number for the formula. I know how what to multiply by when they're simple decimals like 0.5, 0.33, 0.66, 0.25, but how do I know what number to...
by RRahimtoola1I
Thu Oct 03, 2019 3:44 pm
Forum: Balancing Chemical Reactions
Topic: Confusion on H.3
Replies: 2
Views: 99

Confusion on H.3

For Question 3, Section H, I balanced the equation and got:

SiH4 + 2H2O > SiO2 + 4H2

but the answer doubles all the coefficients, even though the way I did it above is balanced. Is there a reason for this?

Thank you in advance!

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