## Search found 65 matches

Mon Jan 18, 2021 10:49 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: neutral solution
Replies: 2
Views: 28

### Re: neutral solution

Just to add, by this he means that if you calculate the [H3O+] to be less than 10^-7, then the amount of H3O+ normally in water caused by the autoprotolysis reaction influences the pH more than the amount of H3O+ generated by an acid. If you calculate that the acid generates 10^-9 M of H3O+ ions, th...
Mon Jan 18, 2021 10:37 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH for Strong Acids
Replies: 2
Views: 13

### Re: pH for Strong Acids

The pH for strong acids is just the negative log of the molar concentration because for strong acids, all of the acid dissociates into H3O+ ions and A- ions (A- refers to the conjugate base of an acid). If the strong acid completes dissociates into H3O+ and A-, then the initial concentration of the ...
Mon Jan 18, 2021 10:32 am
Forum: Phase Changes & Related Calculations
Topic: ionization percentage
Replies: 5
Views: 21

### Re: ionization percentage

Ionization percentage is the amount of acid or base that has turned into its conjugate acid or base. The formula for ionization percentage for acids is [A-]/[HA] * 100% and for bases it's [HB+]/[B] * 100%. The value of HA and B are the initial concentrations of the acid and base before equilibrium h...
Fri Jan 15, 2021 6:27 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Hw promblem 6.3
Replies: 5
Views: 31

### Re: Hw promblem 6.3

Because the initial solution was supposed to be a concentration of 0.025 M, and it is a strong acid, the concentration of H+ would have been 0.025 M. You can find the desired pH by doing -log[0.025]. To find the actual pH, you can use the formula M1V1 = M2V2 to solve for M2. M1 would be 0.025M, V1 ...
Fri Jan 15, 2021 1:44 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Hw promblem 6.3
Replies: 5
Views: 31

### Re: Hw promblem 6.3

Because the initial solution was supposed to be a concentration of 0.025 M, and it is a strong acid, the concentration of H+ would have been 0.025 M. You can find the desired pH by doing -log[0.025]. To find the actual pH, you can use the formula M1V1 = M2V2 to solve for M2. M1 would be 0.025M, V1 w...
Thu Jan 14, 2021 1:29 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Gas
Replies: 16
Views: 67

### Re: Gas

I think you would be given the units of the pressure of a gas. If they ask for a different unit in the answer, then you could just convert between the units, but bar and atm are very similar in value so there is not much difference between their values.
Wed Jan 13, 2021 7:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Net Ionic Equation
Replies: 3
Views: 23

### Re: Net Ionic Equation

In this problem, anything that is aqueous on both sides of the equation would not be in the net ionic equation since it does not change. In this case, Na and NO3 would be removed to form the net ionic equation because they are aqueous on both sides of the equation. Then you just need to take what is...
Tue Jan 12, 2021 2:58 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Sapling Focus Question 5.61
Replies: 3
Views: 31

### Re: Sapling Focus Question 5.61

I believe that adding water to the reaction would not affect the equilibrium since water is a liquid so it would not be included in the equilibrium expression. Because water is in excess and the concentration does not change very much before or after the reaction, adding water to the reaction does n...
Tue Jan 12, 2021 2:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Textbook Focus Problem 5.33 a
Replies: 3
Views: 29

### Re: Textbook Focus Problem 5.33 a

You can tell this reaction would be endothermic because it involves breaking the bond between the two atoms of X. Anytime you are breaking bonds it requires energy so the reaction would be endothermic, taking in heat in order to power the reaction.
Fri Jan 08, 2021 5:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Self Test 5G.3: Using a Net Ionic Equation to Write an Equilibrium Constant
Replies: 1
Views: 12

### Re: Self Test 5G.3: Using a Net Ionic Equation to Write an Equilibrium Constant

For this problem, anything that is aqueous on both sides of the equation would not be in the net ionic equation since it does not change. So in this case Na and NO3 would be removed to form the net ionic equation. This would leave you with 2Ag+(aq) + 2OH-(aq) <--> Ag2O(s) + H2O(l).
Fri Jan 08, 2021 2:03 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling #3
Replies: 5
Views: 26

### Re: Sapling #3

For this problem, you can start by making an ICE table with H2, I2, and HI. You start with 0.300 M of both H2 and I2 based on the moles and liters they give you in the problem. You start with 0 M of HI. You can put these values into the initial concentration row. For the change in concentration, H2 ...
Thu Jan 07, 2021 8:57 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.i #11
Replies: 4
Views: 24

### Re: 5.i #11

Before you plug the values into the equation, you must convert them into moles/L. They start by giving you the values in mmol and give you the volume of 0.500 L so you must convert the mmol to mol and then divide that value by 0.500 L for each. That should give you the correct answer.
Thu Jan 07, 2021 7:02 pm
Forum: Ideal Gases
Topic: Partial Pressure Gas Question
Replies: 4
Views: 23

### Re: Partial Pressure Gas Question

Based on the problem and what you said you did, you should get the correct answer. The equation to use would be PV = nRT or P = nRT/V which is the same thing as P = conc(RT). If you plug in the concentration, correct R value, and temperature in Kelvin, you should get the correct answer. I would doub...
Tue Jan 05, 2021 9:18 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Question #16 from Chemical Equilibrium Part 4 Video Module
Replies: 2
Views: 12

### Re: Question #16 from Chemical Equilibrium Part 4 Video Module

Just to give another way to think about it, heating a reaction would favor the reaction in the endothermic direction. Since the forward reaction is exothermic, the endothermic reaction would be the reverse reaction so this would be favored. Therefore, the equilibrium would shift left. Hope this helps!
Fri Dec 11, 2020 2:04 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: resonance and acid strength
Replies: 3
Views: 51

### Re: resonance and acid strength

Something with more resonance would be a stronger acid because the electrons would be delocalized. Electron delocalization stabilizes molecules and therefore leads to a more stable conjugate base of an acid. If a molecule has more double bonds, there is resonance to delocalize electrons, so this mol...
Thu Dec 10, 2020 8:49 pm
Forum: Amphoteric Compounds
Topic: Amphoteric Oxides
Replies: 2
Views: 31

### Re: Amphoteric Oxides

I think the main way to tell is just that amphoteric oxides follow a diagonal line along the metalloids. The oxides with elements on the left side of the periodic table are basic and those with elements on the right side of the periodic table are acidic, so those in between are amphoteric. These amp...
Wed Dec 09, 2020 6:22 pm
Forum: Trends in The Periodic Table
Topic: effective nuclear charge and shielding
Replies: 2
Views: 26

### Re: effective nuclear charge and shielding

Just to add on, when going left to right across a period, the number of shielding electrons does not increase but the number of protons does increase. This means that the valence electrons are being pulled in by a greater force (from more protons) but there are not more shielding electrons to counte...
Tue Dec 08, 2020 8:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Formal charge when doing VSEPR
Replies: 2
Views: 23

### Re: Formal charge when doing VSEPR

In general you should use formal charges to determine Lewis structures to ensure you have the correct structure. However, when determining molecular shape, it does not matter if a bond is a single or double bond because it is counted as one region of electron density. So if you have a structure with...
Tue Dec 08, 2020 10:49 am
Forum: Determining Molecular Shape (VSEPR)
Topic: textbook 2E17
Replies: 2
Views: 24

### Re: textbook 2E17

To find when the bond angle is slightly less than a value, you look at the number of areas of high electron density. This would include bond areas and lone pairs. In O3, there are two bond regions and one lone pair region, meaning there are 3 regions of electron density. Three regions of electron de...
Fri Dec 04, 2020 7:15 pm
Forum: Naming
Topic: Chelating Ligands
Replies: 3
Views: 32

### Re: Chelating Ligands

Chelating ligands are ligands that attach to a metal atom in two or more areas. This would make them polydentates.
Fri Dec 04, 2020 7:11 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Relative Acidity
Replies: 2
Views: 19

### Re: Relative Acidity

An electron withdrawing atom would be an atom that has the power to pull some electrons away from the atom it is bonded to in order to stabilize the negative charge on that atom by delocalizing electrons. An example he gave is Cl bonded to O versus Br bonded to O in ClOH and BrOH. Cl has a higher el...
Thu Dec 03, 2020 1:49 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Tetrahedral vs Square Planar
Replies: 6
Views: 49

### Re: Tetrahedral vs Square Planar

I think we are just supposed to know that if the coordination number is 4, it could be square planar or tetrahedral, but we don't have to know how to tell which one it is.
Wed Dec 02, 2020 8:36 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: [Pt(en)Cl2] coordination number
Replies: 2
Views: 16

### Re: [Pt(en)Cl2] coordination number

[Pt(en)Cl2] would have a coordination number of 4. This is because there are in total 4 different bonds to the central atom, Pt. There are two Cl which each contribute one bond to the central atom. The (en) stands for ethylenediamine which is a bidentate, meaning it forms two bonds to the central at...
Wed Dec 02, 2020 9:17 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Sapling Week 9 HW Question 2
Replies: 11
Views: 107

### Re: Sapling Week 9 HW Question 2

The coordination number is the number of bonds to the transition metal atom in the coordination complex. The elements in the bracket are the only elements directly bonded to the transition metal atom. Fe would be the central transition metal atom and the 4 Br atoms would be bonded to it, so therefor...
Mon Nov 30, 2020 10:48 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: trigonal bipyramidal electron geometry
Replies: 2
Views: 46

### Re: trigonal bipyramidal electron geometry

For the trigonal bipyramidal arrangement, if the lone pair was in the axial position, it would be 90 degrees from three different bonds (the bonds at the equatorial positions). However, if the lone pair was in the equatorial position, it would only be 90 degrees from 2 bonds (the bonds in the axial ...
Sat Nov 28, 2020 11:46 am
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polar vs. nonpolar bonds/molecules
Replies: 8
Views: 64

### Re: Polar vs. nonpolar bonds/molecules

If there are two of the same atom on each side of a central atom (with no lone pairs on the central atom), the overall molecule would be nonpolar. However, the individual bonds inside the molecule are still polar bonds because they are between different atoms, but because the molecule is linear, it ...
Fri Nov 27, 2020 8:31 pm
Forum: Sigma & Pi Bonds
Topic: Sapling Learning Week 7 and 8 Homework Question 16
Replies: 4
Views: 22

### Re: Sapling Learning Week 7 and 8 Homework Question 16

Something has a delocalized pi bond when it has resonance structures that each have a different location for one pi bond. In other words, if a pi bond can be drawn in different places, then that pi bond would be delocalized. For this question, out of the three in the first part of the question that ...
Wed Nov 25, 2020 12:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Negative Pole on Molecule
Replies: 2
Views: 20

### Re: Negative Pole on Molecule

The negative pole on a molecule would be on the atom in a bond with a higher electronegativity. If the atoms in a bond are not the same, there will be a negative and positive pole, even if it is very small. If oxygen is bonded to hydrogen, oxygen would have the negative pole because it has a higher ...
Tue Nov 24, 2020 10:26 pm
Forum: Ionic & Covalent Bonds
Topic: Valence in d-block
Replies: 4
Views: 34

### Re: Valence in d-block

To find the valence electrons in the d-block, you should include the s-block electrons from the period of that element as well as any d-block electrons in that period. You can do this by counting over from the left side of the periodic table towards the element. For example, Mn would have 7 valence ...
Tue Nov 24, 2020 2:00 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape vs. Electron Arrangement
Replies: 4
Views: 28

### Re: Shape vs. Electron Arrangement

Often times, the electron arrangement differs from the shape when there are lone pairs in a molecule. The electron arrangement of a molecule is where there are regions of electron density, whether that be bonds or lone pairs. However, when finding the shape of a molecule, you only pay attention to t...
Fri Nov 20, 2020 11:05 am
Forum: Resonance Structures
Topic: Sapling Resonance Structures
Replies: 4
Views: 66

### Re: Sapling Resonance Structures

Another thing to note is that if a resonance structure is very unfavorable, it will contribute very little to the overall resonance hybrid, but it still contributes a very small amount because it is a possible resonance structure. The most favorable and lowest energy resonance structures contribute ...
Thu Nov 19, 2020 9:18 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Textbook Exercise 2A.17
Replies: 1
Views: 22

### Re: Textbook Exercise 2A.17

Mn would normally have 5 electrons in the 3d subshell and 2 electrons in the 4s subshell. If it were to lose 3 electrons, it would lose them from the 4s subshell first because it is higher in energy when it is filled and then it would lose 2 additional electrons from the 3d subshell to lose a total ...
Wed Nov 18, 2020 1:26 pm
Forum: Lewis Structures
Topic: Lewis Structure Covalent Bonds
Replies: 2
Views: 24

### Re: Lewis Structure Covalent Bonds

Often Lewis structures are used to show covalent bonds, but there are also Lewis structures to represent ionic bonds. An example would be for NaCl, where you would draw a Na+ ion with a bracket showing its + charge and a Cl- ion next to it with 8 lone pairs representing its full valence shell, as we...
Wed Nov 18, 2020 1:16 pm
Forum: Resonance Structures
Topic: Resonance
Replies: 11
Views: 83

### Re: Resonance

Just to add, elements want to have the same amount of electrons belonging to them as they have valence electrons, so the more atoms that can fulfill this requirement the better the structure. Some atoms are more likely to accept a negative formal charge due to their electronegativity, and some atoms...
Mon Nov 16, 2020 11:56 pm
Forum: Dipole Moments
Topic: Dipole Moments Always Exist?
Replies: 3
Views: 40

### Re: Dipole Moments Always Exist?

There are dipoles between any two atoms that aren't the same, they are just very small for some atoms. Between C and H, there is a dipole but it is very small because their electronegativities are very similar. If the same atom is bonded to itself, there is no dipole. Also one thing to note is that ...
Wed Nov 11, 2020 2:04 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4s and 3d Orbitals
Replies: 1
Views: 16

### Re: 4s and 3d Orbitals

The 4s orbital is not higher in energy until it has been filled. So for K, Ca, and any element after Ca, the 4s is lower in energy while it is empty. This would cause electrons to fill that subshell before the 3d subshell. Once the 4s subshell is filled, it would become higher in energy than 3d agai...
Wed Nov 11, 2020 2:01 pm
Forum: Bond Lengths & Energies
Topic: Energy per mole
Replies: 2
Views: 25

### Re: Energy per mole

Yes, I believe that for 1 mole of Na+ and 1 mole of Cl- interacting, the total energy of their interactions is -250 kJ.
Mon Nov 09, 2020 8:45 pm
Forum: Ionic & Covalent Bonds
Topic: Textbook Question 2A.15 Part D
Replies: 1
Views: 18

### Re: Textbook Question 2A.15 Part D

The reason Ga would form an ion of 3+ is because it has 3 electrons in its outer shell, 1 in the 4p subshell and 2 in the 4s subshell. If Ga were to become an ion, it would lose all of the electrons in its outermost shell, which would be 3 electrons. It would not lose the electrons in the 3d subshel...
Mon Nov 09, 2020 8:41 pm
Forum: Resonance Structures
Topic: oxidation numbers in regards to resonance
Replies: 2
Views: 28

### Re: oxidation numbers in regards to resonance

For that question, I believe the way to solve it is to find the atom with the formal charge as close as possible to the oxidation number. So if the oxidation number of an atom is 7+, you would choose the resonance structure with the atom that has a formal charge closest to 7+. Hope this helps!
Mon Nov 09, 2020 6:31 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Lowering Formal Charges
Replies: 7
Views: 58

### Re: Lowering Formal Charges

For some molecules, not all the formal charges can be zero. This is because if you add up all the formal charges of atoms in a molecule, you get the overall charge of that molecule. So for a molecule with a 2+ charge, the formal charges of the atoms have to add up to that value so some of the atoms ...
Fri Nov 06, 2020 9:03 am
Forum: Resonance Structures
Topic: Ample and overwhelming bond character
Replies: 1
Views: 40

### Re: Ample and overwhelming bond character

If you are referring to the sapling homework, they are talking about bond character in terms of the length of the bond between two atoms. If the bond is a double bond, that bond would be shorter than a single bond between the two same atoms. When sapling asks if a bond is ample in one property, it i...
Thu Nov 05, 2020 11:56 pm
Forum: Ionic & Covalent Bonds
Topic: 2A.19 Ground state electron configuration for ions
Replies: 3
Views: 29

### Re: 2A.19 Ground state electron configuration for ions

For Ni(2+), the Nickel neutral atom has lost 2 electrons. The electron configuration for a neutral Nickel atom would be [Ar]3d84s2. When Nickel loses 2 electrons to become Ni(2+), the electrons are lost from the 4s subshell because when it is filled it is higher in energy than the 3d subshell. Becau...
Wed Nov 04, 2020 10:19 am
Forum: Lewis Structures
Topic: Electrons in Lewis Structures
Replies: 8
Views: 41

### Re: Electrons in Lewis Structures

To determine the valence electrons for each element, you can look at the group number of that element. For group 1 and 2, they each have 1 and 2 valence electrons respectively, meaning they have the same amount of valence electrons as their group number. For groups 13-18, you have to subtract 10 fro...
Wed Nov 04, 2020 9:39 am
Forum: Quantum Numbers and The H-Atom
Topic: subshells and orbitals
Replies: 9
Views: 95

### Re: subshells and orbitals

To expand, orbitals are part of subshells, and can hold either the same or less electrons. One example of a subshell would be 2s, which can only hold 2 electrons because it contains one orbital (and each orbital holds 2 electrons). However, the subshell 2p has three orbitals in it so it can hold 6 e...
Tue Nov 03, 2020 5:12 pm
Forum: Trends in The Periodic Table
Replies: 8
Views: 62

### Re: Ionic Radius

For elements with the same number of electrons, the atom with more protons in the nucleus or the higher effective nuclear charge has the smaller atomic radius. In the case of Na+ and F-, Na+ has the smaller ionic radius because it has a stronger pull from the nucleus, causing electrons to be pulled ...
Fri Oct 30, 2020 1:59 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Sapling #24
Replies: 5
Views: 76

### Re: Sapling #24

If you look at the periodic table, you can see that oxygen has 4 electrons in the p-block. The p-block only has 3 orbitals, so two of those electrons are paired up in one orbital with opposite spins. If you were to take one of those electrons away, there would be 3 p-block electrons and they could e...
Thu Oct 29, 2020 3:28 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: l=4
Replies: 13
Views: 85

### Re: l=4

I think he said in the lecture that in theory l could be equal to 4, but we don't have elements that are this high. So in the periodic table, there are no elements with l=4.
Thu Oct 29, 2020 1:51 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Sapling Bohr orbits of the hydrogen atom
Replies: 2
Views: 11

### Re: Sapling Bohr orbits of the hydrogen atom

Yes, the wave must connect at both ends by having a full wavelength. It must also have a constant wavelength and amplitude throughout the whole wave so it does not vary.
Tue Oct 27, 2020 1:50 pm
Forum: Photoelectric Effect
Topic: Energy of photon
Replies: 5
Views: 54

### Re: Energy of photon

I believe the energy of Ep is usually given in J/photon, but pay attention to the question to make sure your units match for each of the values in that equation. If you have the energy in J/photon, you can multiply by Avogadro's number to get J/mol of photon.
Tue Oct 27, 2020 1:46 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Textbook Problem 1B27
Replies: 6
Views: 81

### Re: Textbook Problem 1B27

SI units are always in kg, not g. Because of this, the constant h used in the Heisenberg's indeterminacy equation is in units of J/s, and 1 J = 1 kg m^2 s^-2. Because the constant h uses kg, you must use units of kg for the mass.
Fri Oct 23, 2020 8:22 am
Forum: Limiting Reactant Calculations
Topic: Ammonia Percent Yield (Workshop)
Replies: 1
Views: 31

### Re: Ammonia Percent Yield (Workshop)

Yes, that would be the correct way to solve the problem. I got a slightly different answer for the yield of NO from 15.6g NH3 (I got 27.49g NO produced) but either way O2 is still the limiting reactant and your answer would be correct.
Thu Oct 22, 2020 3:24 pm
Forum: Photoelectric Effect
Topic: Textbook Problem 1A. 9
Replies: 4
Views: 45

### Re: Textbook Problem 1A. 9

For this problem, you can figure out the event based on the wavelength of the electromagnetic radiation. For your example, the wavelength is 340 nm, which is in the ultraviolet portion of the electromagnetic spectrum, so this event is acquiring a suntan. By comparing each wavelength calculated to th...
Wed Oct 21, 2020 4:21 pm
Forum: Properties of Electrons
Topic: Properties of Electrons and Matter as a Whole
Replies: 5
Views: 51

### Re: Properties of Electrons and Matter as a Whole

Yes, you are correct. While all matter has wavelike properties, it can only be detected at a small mass due to De Broglie's equation, wavelength = h/p. Also, electrons do have both wave and particle like properties.
Tue Oct 20, 2020 4:05 pm
Forum: Significant Figures
Topic: How would you round these numbers
Replies: 10
Views: 118

### Re: How would you round these numbers

I believe that rounding those answers to 8.0 and 5.0 is correct if using two sig figs.
Mon Oct 19, 2020 4:23 pm
Forum: Photoelectric Effect
Topic: When to use E = h(nu) and not to
Replies: 3
Views: 35

### Re: When to use E = h(nu) and not to

Yes, you are correct. Because E(photon) - work function = Ek, you could rearrange this so work function = E(photon) - Ek. This means that the energy required to remove an electron is the (energy of a photon) - (kinetic energy of the ejected electron).
Wed Oct 14, 2020 8:12 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Series
Replies: 2
Views: 67

### Re: Series

What those statements mean is that for each of the series, it involves electrons starting at a certain electron energy level and being excited to a higher level, or starting at various high energy levels and jumping back down to one standard energy level. For the Lyman series, which is in the ultrav...
Wed Oct 14, 2020 7:55 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Wavelength for Atomic Spectroscopy
Replies: 3
Views: 49

### Re: Wavelength for Atomic Spectroscopy

Yes, more energy is required for an electron to jump from n=1 to n=5 than from n=2 to n=4. Because of this, a shorter wavelength of light must be emitted when going from n=5 to n=1 because shorter wavelengths contain more energy. The transition from n=4 to n=2 would emit longer wavelength light beca...
Tue Oct 13, 2020 9:24 pm
Forum: Properties of Light
Topic: Finding kinetic energy
Replies: 3
Views: 66

### Re: Finding kinetic energy

You use the mass of an electron, 9.109 * 10^-31 kg, which can be found in the back of the book. You know to use this mass because you use the mass of the object you need to find the kinetic energy of. Since in this situation you are finding the kinetic energy of an electron, you use the mass of an e...
Tue Oct 13, 2020 11:47 am
Forum: Photoelectric Effect
Topic: Light Intensity
Replies: 5
Views: 62

### Re: Light Intensity

My understanding is that light intensity is simply how bright a light is, and increasing the intensity increases the amount of photons being emitted by that light source. The wavelength and frequency are independent of the amplitude, and are instead dependent on the length of a wave. So changing the...
Tue Oct 13, 2020 11:33 am
Forum: Quantum Numbers and The H-Atom
Topic: Atomic Spectra Post Assessment #42
Replies: 2
Views: 44

### Re: Atomic Spectra Post Assessment #42

For this problem, you start by turning the frequency into energy using E = hv. Then, you calculate the energy of the n=4 level by using the En = -hR/n^2 equation. Because Efinal - Einitial = difference in energy, you can plug in the energy difference you calculated using the frequency (which should ...
Wed Oct 07, 2020 10:29 am
Forum: Limiting Reactant Calculations
Topic: Limiting reactants
Replies: 8
Views: 80

### Re: Limiting reactants

If the molar ratio was equal to the calculated moles that would mean there is no limiting reactant because each reactant has the perfect amount of moles to react with each other. To find the amount of product formed you could use moles of either reactant because they both are able to produce the sam...
Wed Oct 07, 2020 10:23 am
Forum: Molarity, Solutions, Dilutions
Topic: G.21 Homework Problem
Replies: 7
Views: 73

### Re: G.21 Homework Problem

For this problem, I start by converting the 0.500 grams of KCl, K2S, and K3PO4 all into moles by using their molar masses. Once I had the moles, I knew the moles of KCl = moles of K, 1 mole of K2S = 2 mole K, and 1 mole K3PO4 = 3 mole K. I used these conversion factors to convert from moles of each ...
Tue Oct 06, 2020 10:36 am
Forum: Significant Figures
Topic: Tips for counting sig figs?
Replies: 9
Views: 86

### Re: Tips for counting sig figs?

If a number has decimal places, it usually has the same amount of sig figs as digits in the number. For example, 4.00, 40.2, and 5.46 all have 3 sig figs because they all have 3 digits. However, in a number like 0.029, there are no digits present before the 2, so this value would only have 2 sig fig...
Mon Oct 05, 2020 2:18 pm
Forum: Molarity, Solutions, Dilutions
Topic: Molar mass for O2 vs O
Replies: 11
Views: 116

### Re: Molar mass for O2 vs O

Because a molecule of O2 has two oxygen atoms instead of just one, the total mass would be 32 g/mol rather than 16 g/mol which is for just one oxygen atom.
Mon Oct 05, 2020 2:12 pm
Forum: Significant Figures
Topic: M.3
Replies: 4
Views: 43

### Re: M.3

In this problem, it is also mentioned that there are 17.5g of CO2 produced from the thermal decomposition, which has 3 sig figs. Because the last step involves the 17.5g, the answer should be 93.1% with 3 sig figs.

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