Search found 33 matches
- Tue Dec 04, 2018 11:08 am
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Why is HCOOH a stronger acid than CH3COOH? [ENDORSED]
- Replies: 2
- Views: 556
Re: Why is HCOOH a stronger acid than CH3COOH? [ENDORSED]
Electron donating groups like CH3 basically destabilize the conjugate base anion because it donates its electrons such that the negative charge on COO- will intensify. This will ultimately make it less stable. Conversely, electron withdrawing groups will stabilize the conjugate base anion because it...
- Tue Dec 04, 2018 11:04 am
- Forum: Lewis Acids & Bases
- Topic: Ionic equation
- Replies: 1
- Views: 215
Re: Ionic equation
For acid-base reactions in which there is a weak acid or weak base, the textbook states to write the weak acid/base as the undissociated form in the ionic equation. This is because they dissociate to a small extent such that the dominant species in the solution will be its undissociated form. So, on...
- Tue Dec 04, 2018 11:01 am
- Forum: Conjugate Acids & Bases
- Topic: Conjugate of oxoacid
- Replies: 3
- Views: 375
Re: Conjugate of oxoacid
Yes, thank you!
- Mon Dec 03, 2018 1:57 pm
- Forum: Conjugate Acids & Bases
- Topic: Conjugate of oxoacid
- Replies: 3
- Views: 375
Conjugate of oxoacid
In the stabilization of oxoacid conjugates (like CCl3COO- or CBr3COO-) in which there are electron withdrawing atoms such as halogens, does it matter if the halogen is less electronegative than the oxygen atom?
- Tue Nov 27, 2018 11:53 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Central atom
- Replies: 5
- Views: 529
Re: Central atom
Generally, the central atom is the atom that has the lowest ionisation energy. Ionisation energy increases across a period and decreases down a group.
- Tue Nov 27, 2018 10:18 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond angle
- Replies: 5
- Views: 1644
Re: Bond angle
i think AX2E has a bent shape with a bond angle that will be less than 120 degrees while AX2E2 also has a bent shape but with angles less than 109.5 degrees. This is on the basis that, AX2E comes from a trigonal planar shape with one corner of the triangle being a lone pair instead. Trigonal planar ...
- Mon Nov 26, 2018 3:18 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Less than Angles
- Replies: 2
- Views: 647
Re: Less than Angles
Just to add on, lone pair-lone pair repulsion > lone pair-bond pair repulsion > bond pair-bond pair repulsion. In the tetrahedral example mentioned by Kayla, the bond angle between the atoms in a trigonal pyramidal shape becomes less than 109.5 because the lone pair-bond pair repulsion is greater th...
- Thu Nov 22, 2018 1:05 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Does formal charge apply to the VSEPR Model?
- Replies: 6
- Views: 1789
Re: Does formal charge apply to the VSEPR Model?
I would assume so. Since the molecule will preferentially form the most stable structure.
- Tue Nov 20, 2018 12:06 pm
- Forum: Ionic & Covalent Bonds
- Topic: strength of bonds
- Replies: 1
- Views: 249
Re: strength of bonds
I think knowing its exact bond dissociation energy is only helpful if you want to compare exact values or make calculations. But for predicting which is stronger, in general, ionic bonding will be stronger than dipole-dipole interactions.
- Mon Nov 19, 2018 3:43 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Atom Placement
- Replies: 4
- Views: 411
Re: Atom Placement
SO2Cl2 has a tetrahedral shape. So it doesn't matter where you put the Cl or O atoms because it will be the same regardless.
- Tue Nov 13, 2018 10:36 pm
- Forum: Hybridization
- Topic: Bond Angels
- Replies: 5
- Views: 704
Re: Bond Angels
Bond angles are formed when electron pairs repel each other. The electron pairs will assume a geometry that keeps them as far apart from each other as possible because of this repulsion.
- Mon Nov 12, 2018 1:11 pm
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: Energy of Bonds
- Replies: 3
- Views: 375
Re: Energy of Bonds
I think the energy of the bonds have already been experimentally determined.
- Mon Nov 12, 2018 1:09 pm
- Forum: Ionic & Covalent Bonds
- Topic: Boiling Point
- Replies: 3
- Views: 2991
Re: Boiling Point
It depends on the kind of molecules/compounds you want to compare. For CHCl3 and CCl4 you are comparing the types of intermolecular forces of attraction between the molecules. CHCl3 is a polar molecule while CCl4 is a non-polar molecule. Dipole forces are the dominant intermolecular forces of attrac...
- Wed Nov 07, 2018 12:58 pm
- Forum: Lewis Structures
- Topic: Formal Charge
- Replies: 14
- Views: 1318
Re: Formal Charge
I think it depends on the electronegativity of the atom. For example in SO3-, the O will more likely take on the negative charge because it is more electronegative than S and hence will draw electrons more strongly to itself compared to S.
- Tue Nov 06, 2018 11:38 am
- Forum: Octet Exceptions
- Topic: Octet Exceptions
- Replies: 4
- Views: 411
Re: Octet Exceptions
To add on, the elements in period 3 and below can exceed an octet because it has d orbitals. These d orbitals are energetically accessible and can hence have an expanded octet. Elements that are in the second period cannot exceed 8 electrons because there are only 2s and 2p sub-shells that can hold ...
- Mon Nov 05, 2018 4:45 pm
- Forum: Trends in The Periodic Table
- Topic: Periodic Trends in Relation
- Replies: 3
- Views: 772
Re: Periodic Trends in Relation
1. Atomic radius generally increases down a group and decreases across a period. Down a group, valence electrons are in shells that are further away from the nucleus and hence atomic radius increases down the group. Across a period there is a decrease because effective nuclear charge increases and v...
- Tue Oct 30, 2018 9:46 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron Affinity
- Replies: 2
- Views: 281
Re: Electron Affinity
The electron is added to an atom in its gaseous state!
- Tue Oct 30, 2018 9:45 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron Affinity
- Replies: 2
- Views: 281
Re: Electron Affinity
A gas-phase atom is an atom in the gaseous phase.
- Tue Oct 30, 2018 10:26 am
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: exceptions
- Replies: 6
- Views: 897
Re: exceptions
The half filled 3d orbital is more stable. So 3d^5 4s^1 is more stable than 3d^4 4s^2 and hence results in the different electron configuration.
- Mon Oct 29, 2018 10:29 pm
- Forum: Ionic & Covalent Bonds
- Topic: Ion formation and unpaired e-
- Replies: 2
- Views: 255
Re: Ion formation and unpaired e-
To add on, this happens because when the d orbitals are half or fully filled the atom/ion will be more stable!
- Wed Oct 24, 2018 4:56 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Quantum numbers for the "exception" cases
- Replies: 15
- Views: 2464
Re: Quantum numbers for the "exception" cases
Quantum numbers are basically used to describe an electrons position in the atom. So it is not the atoms that have quantum numbers but the electrons in the atom. Electrons in the atoms could have the same 4 quantum numbers for example the electron in the 4s orbital in either copper or potassium with...
- Tue Oct 23, 2018 6:21 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electronic Config of tungsten (1E.13)
- Replies: 1
- Views: 713
Re: Electronic Config of tungsten (1E.13)
The orbitals in Xe are filled in this order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d . So the 6s orbital has to be filled first, then the 4f orbital and then the 5d orbital. In Cr the orbitals are filled in this order: 1s, 2s, 2p, 3s, 3p, 4s, 3d. Since a half-filled 3d orbital is more...
- Mon Oct 22, 2018 9:13 am
- Forum: Photoelectric Effect
- Topic: Question 1B.15 Part B
- Replies: 1
- Views: 267
Re: Question 1B.15 Part B
E = hv is the energy of a photon. The energy of the incoming photon must match the work function in order for an electron to be removed from the surface of the metal. I think then E = hv would be the same as the work function.
- Wed Oct 17, 2018 9:46 pm
- Forum: Properties of Light
- Topic: Problem 1.7 conversion of meters to nanometers
- Replies: 2
- Views: 495
Re: Problem 1.7 conversion of meters to nanometers
1 m = 1 x 10^9 nm and conversely 1 nm = 1 x 10^-9 m.
So, 4.2 x 10^-7 m converted to nm will be 4.2 x 10^-7 x 10^9 nm which is just 420 nm after the powers cancel out.
Hope this helps!
So, 4.2 x 10^-7 m converted to nm will be 4.2 x 10^-7 x 10^9 nm which is just 420 nm after the powers cancel out.
Hope this helps!
- Wed Oct 17, 2018 3:55 pm
- Forum: Photoelectric Effect
- Topic: Speed of Light
- Replies: 5
- Views: 442
Re: Speed of Light
I think it is because it isn't possible for a speed to be greater than the speed of light. So the electron's velocity being greater than the speed of light is impossible and would either mean it was done wrongly or the question might for example state that the model being tested is incorrect, like t...
- Mon Oct 15, 2018 9:04 am
- Forum: Properties of Light
- Topic: Threshold energy
- Replies: 2
- Views: 289
Re: Threshold energy
With regards to the photoelectric experiment, the threshold energy is the minimum energy needed to remove an electron from its metal. In the equation: (E=hv) - threshold energy = (Ek = 1/2me-ve^2) E=hv is the energy per photon and this energy must be equal to or more than the threshold energy for an...
- Thu Oct 11, 2018 11:42 am
- Forum: Limiting Reactant Calculations
- Topic: Homework question L.35 part 1 [ENDORSED]
- Replies: 1
- Views: 456
Re: Homework question L.35 part 1 [ENDORSED]
Hi! The mass of the crucible remains constant. We can find the mass of the product first. Mass of product = 28.35 - 26.45 = 1.90 g (2dp) Since a type of tin oxide was formed and the mass of tin in this tin oxide should not change, we can find the mass of oxygen in the product by subtract the mass of...
- Wed Oct 10, 2018 3:44 pm
- Forum: Properties of Electrons
- Topic: Energy levels and electrons
- Replies: 2
- Views: 161
Re: Energy levels and electrons
En = -(hR)/n^2 for n = 1,2, ... ∞) In the equation, R and h are both constants and so hR will remain the same for any value of n. When n becomes larger and larger, En becomes smaller and smaller. This is such that as n approaches ∞, En will approach 0. So if the energy level is very high, the energy...
- Tue Oct 09, 2018 3:39 pm
- Forum: Photoelectric Effect
- Topic: Vacuum
- Replies: 4
- Views: 333
Re: Vacuum
I think Dr. Lavelle mentioned that the experiment needs to take place in a vacuum so that the electrons that are ejected will not react with particles in the air.
- Fri Oct 05, 2018 9:11 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: 6th edition: E15
- Replies: 2
- Views: 265
Re: 6th edition: E15
Sulfide refers to the metal sulfide of M which would have the formula MS. OH has a charge of -1 and so in M(OH)2 M has a charge of +2. S has a charge of -2 and so you need to find the Mr of MS.
- Thu Oct 04, 2018 11:33 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Problem F.7
- Replies: 4
- Views: 1540
Re: HW Problem F.7
Let Mr of M be x. % composition = 88.8% Form an equation in x using the formula, % composition = (mass of M / mass of M2O) x 100%. [2x/(2x+16.00)] x 100% = 88.8% Then use algebra to solve for x. 2x/(2x+16.00) = 0.888 2x = 1.776x + 14.208 0.224x = 14.208 Eventually you will get x = 63.4 g/mol Mr of M...
- Tue Oct 02, 2018 7:11 pm
- Forum: General Science Questions
- Topic: Limiting Reactant Calculations
- Replies: 2
- Views: 878
Re: Limiting Reactant Calculations
Hi! Since 1.000kg of AgNO3 is used, C6H9Cl3 is the limiting reactant as AgNO3 is in excess. Find the number of moles of C6H9Cl3 by taking 0.750 divided by the Mr 187.50 g/mol. Number of moles of C6H9Cl3 = 0.750/187.50 = 0.00400 mol The number of moles of AgCl produced is the same as the number of mo...
- Tue Oct 02, 2018 4:22 pm
- Forum: Limiting Reactant Calculations
- Topic: Homework Question M9
- Replies: 1
- Views: 241
Re: Homework Question M9
Hi! For Q9 the net ionic equation will cancel out all the ions that remained in the aqueous form. The molecular equation will have all molecules written in it. Eg. Cu(NO3)2 + 2NaOH -> Cu(OH)2 + 2NaNO3 However, to fin the net ionic equation it will look something like this. Rough equation: Cu2+(aq) +...