Search found 61 matches

by Alan Wu
Sun Dec 01, 2019 1:42 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted or Lewis Definition?
Replies: 6
Views: 29

Re: Bronsted or Lewis Definition?

NaOH, the entire compound, is considered a base (a STRONG base, even). A bronsted base is defined as anything that accepts a proton. But the textbook explicitly states that Na+ is the spectator ion and OH- alone is the Bronsted Base. It warns us to not confuse it with what you said about NaOH being...
by Alan Wu
Sun Dec 01, 2019 12:47 am
Forum: Bronsted Acids & Bases
Topic: Bronsted or Lewis Definition?
Replies: 6
Views: 29

Re: Bronsted or Lewis Definition?

NaOH, the entire compound, is considered a base (a STRONG base, even). A bronsted base is defined as anything that accepts a proton. But the textbook explicitly states that Na+ is the spectator ion and OH- alone is the Bronsted Base. It warns us to not confuse it with what you said about NaOH being...
by Alan Wu
Sat Nov 30, 2019 11:07 pm
Forum: Amphoteric Compounds
Topic: Amphoteric Compounds - do we need to memorize them?
Replies: 2
Views: 23

Amphoteric Compounds - do we need to memorize them?

Are we required to memorize all the amphoteric oxides shown in Figure 6A.7 on page 450 for the final exam? And what exactly do we have to know about amphoteric compounds? Is it the fact that they can react with both acids and bases? Let's say we're given an oxide and we're unsure if it's amphoteric ...
by Alan Wu
Sat Nov 30, 2019 10:03 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted or Lewis Definition?
Replies: 6
Views: 29

Bronsted or Lewis Definition?

For the upcoming final, which definition of acids and bases are we supposed to use by default?

Also, for Bronsted Bases, are we allowed to refer to NaOH (the entire compound) as a base? Or do we have to specifically point out that OH- is the Bronsted Base while Na+ is just a spectator ion?
by Alan Wu
Sat Nov 30, 2019 9:59 pm
Forum: Bronsted Acids & Bases
Topic: J.21
Replies: 1
Views: 13

Re: J.21

Yes, just take the grams of Na3AsO4 and divide it by its molar mass. Then remember to multiply the result by 3, because there are 3 moles of Na for every mole of the compound.
by Alan Wu
Sat Nov 30, 2019 9:58 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted Base and Acid
Replies: 5
Views: 22

Re: Bronsted Base and Acid

Yes.
A Bronsted Acid donates a proton. (It is the entire compound that donates the H+ proton, e.g. HCl)
A Bronsted Base accepts a proton. (It is just the species that accepts the H+ proton, not including the spectator ion, e.g. OH-, not NaOH)
by Alan Wu
Sat Nov 30, 2019 2:25 pm
Forum: Industrial Examples
Topic: What do we need to know?
Replies: 15
Views: 89

What do we need to know?

Regarding industrial examples of coordination compounds, is Cis-platin as the chemotherapy drug the only example we need to know for the final?
Are there any other industrial examples of coordination compounds that we should know?
by Alan Wu
Sat Nov 30, 2019 2:16 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: Test 2 Number of Hydrogen Bonding Sites on Caffeine
Replies: 2
Views: 43

Test 2 Number of Hydrogen Bonding Sites on Caffeine

How many hydrogen bonding sites are on caffeine? https://us-static.z-dn.net/files/dfd/7d0fd265f1e9dddec8043e926cfb1571.png There are 8 lone pairs of electrons in total on N and O atoms in caffeine. There are no H atoms bonded to N, O, or F atoms in caffeine. Therefore, shouldn't the number of hydrog...
by Alan Wu
Sat Nov 23, 2019 6:06 pm
Forum: Biological Examples
Topic: What should we know for the final?
Replies: 9
Views: 362

Re: What should we know for the final?

BenJohnson1H wrote:Without myoglobin, is hemoglobin square planer about Fe?


Isn't hemoglobin just 4 myoglobin-like molecules joined together? It should have the same shape I believe?
by Alan Wu
Sat Nov 23, 2019 6:04 pm
Forum: Biological Examples
Topic: Heme Complex
Replies: 5
Views: 33

Re: Heme Complex

Fe is always at the center of the Heme Complex. The reason he talked about the heme complex is because it is a coordination complex. And all coordination complexes are made up of a transition metal as the central atom, which is then bonded to numerous ligands.
by Alan Wu
Sat Nov 23, 2019 6:02 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate ligands
Replies: 1
Views: 13

Polydentate ligands

How do we precisely know if a ligand is polydentate? For example, the O in water has 2 lone pairs of electrons, but it is monodentate. Then oxalate has 4 Os, each with 2 lone pairs of electrons, but it is bidentate. Why is that the case?
by Alan Wu
Sat Nov 23, 2019 5:59 pm
Forum: Naming
Topic: Textbook question 9C.1
Replies: 2
Views: 15

Re: Textbook question 9C.1

There's one water molecule ligand and 5 cyanide ligands (cyano) surrounding cobalt (III) in the coordination sphere.
by Alan Wu
Sat Nov 23, 2019 4:34 pm
Forum: Hybridization
Topic: Sigma and Pi Bonds
Replies: 6
Views: 23

Re: Sigma and Pi Bonds

If the orbitals that form sigma bonds overlap more than the pi bonds, how is it that sigma bonds can rotate and have more flexibility than the pi bonds? Sigma bonds overlap in a different way. Use the dumbbell example I mentioned above. If 2 dumbbells are merged together on one end (like orbitals i...
by Alan Wu
Sat Nov 23, 2019 4:32 pm
Forum: Hybridization
Topic: Hybridization with lone pairs on central atom
Replies: 6
Views: 25

Re: Hybridization with lone pairs on central atom

Yes, this can happen. The number of electron density regions equals the number of hybrid orbitals created. However, the lone pairs would be already-paired electrons in these hybrid orbitals. The unpaired electrons, on the other hand, are responsible for forming bonds with the orbitals of other atoms.
by Alan Wu
Sat Nov 23, 2019 4:14 pm
Forum: Hybridization
Topic: Sigma and Pi Bonds
Replies: 6
Views: 23

Re: Sigma and Pi Bonds

The orbitals forming a sigma bond overlap end to end. Just imagine 2 dumbbells flat on the floor, with one of their ends completely merged together. The orbitals forming a pi bond overlap side to side. Just imagine 2 dumbbells standing side by side on the floor, with each of their ends touching each...
by Alan Wu
Sat Nov 23, 2019 4:11 pm
Forum: Hybridization
Topic: 2F15
Replies: 4
Views: 21

Re: 2F15

As the hybridized orbital has more s character (meaning less p character), the less regions of electron density are around a particular atom. For instance, if we compare sp3 to sp2, the s character increased (25% to 33%) and there is one less region of electron density, so the shape went from a tet...
by Alan Wu
Fri Nov 15, 2019 6:37 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: why are double bonds equally weighted as single ones when drawing models?
Replies: 10
Views: 52

Re: why are double bonds equally weighted as single ones when drawing models?

No. It's important to remember that in molecules with both single and multiple bonds, there only exist hybrid bonds of equal energy, and the localized double bonds depicted in lewis structures only exist as a limitation of lewis structures. This is why resonance structures exist: because the multip...
by Alan Wu
Fri Nov 15, 2019 6:29 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Formula Exceptions
Replies: 6
Views: 34

Re: VSEPR Formula Exceptions

This isn't really an exception, but consider AX2E3. This will give you a linear molecule, with bond angle 180 degrees, as opposed to angular or bent.
by Alan Wu
Fri Nov 15, 2019 6:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 2E.21 c
Replies: 2
Views: 14

Re: 2E.21 c

Definitely the one with the double bond between S and O. That gives O a formal charge of zero. In general, you should always try giving O or any Group 16 element a double bond and 2 lone pairs if possible.
by Alan Wu
Fri Nov 15, 2019 6:25 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: C2H4
Replies: 3
Views: 24

Re: C2H4

In C2H4, consider each carbon as a central atom by itself. Each carbon atom has 3 electron density regions around it, so each carbon can have the VSEPR formula AX3. Therefore, there's essentially 2 trigonal planar molecules joined together in C2H4, so the bond angles are around 120 degrees.
by Alan Wu
Fri Nov 15, 2019 6:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: How to tell polar or non polar from lewis structure?
Replies: 9
Views: 52

Re: How to tell polar or non polar from lewis structure?

If the dipole moments in a lewis structure cancel out, then the molecule will be nonpolar.
If there are lone pairs of e-, the molecule is almost always polar.
If the dipole moments don't cancel out and point in one general direction, then the molecule is polar.
by Alan Wu
Fri Nov 15, 2019 6:19 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Angular/Bent Angles
Replies: 3
Views: 20

Angular/Bent Angles

Why if a molecule has AX2E1 or AX2E2, the bond angle is slightly less than 120 degrees and not 180 degrees?

Isn't a linear shape 180 degrees??
by Alan Wu
Fri Nov 08, 2019 6:53 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: Interaction Potential Energy
Replies: 3
Views: 27

Re: Interaction Potential Energy

It is negative because the attractive forces are lowering the energy of the molecule by pulling them closer together. In contrast, the energy you put in to break the bonds would have a positive value.
by Alan Wu
Fri Nov 08, 2019 6:50 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: Vapor Pressure
Replies: 2
Views: 18

Re: Vapor Pressure

Vapor pressure is a measure of the pressure exerted by a gas above a liquid in a sealed container. Strong intermolecular forces produce a lower rate of evaporation and a lower vapor pressure. Weak intermolecular forces produce a higher rate of evaporation and a higher vapor pressure.
by Alan Wu
Fri Nov 08, 2019 6:49 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: Differences between the intermolecular forces
Replies: 2
Views: 16

Re: Differences between the intermolecular forces

The terms induced dipole - induced dipole, London, Dispersion, and Van der Waals forces all describe the same force in this class.
by Alan Wu
Fri Nov 08, 2019 6:48 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: Hydrogen bonding
Replies: 8
Views: 32

Re: Hydrogen bonding

Only highly electronegative atoms are strong enough (negative in charge) to attract the H atom, which has a positive dipole and literally acts like a proton.
by Alan Wu
Fri Nov 08, 2019 6:47 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: Differences
Replies: 1
Views: 15

Re: Differences

Yes, these intermolecular forces are inherently different from each other. Dipole-dipole: an attractive force between 2 polar covalent molecules exhibiting dipoles. Hydrogen bonding: an attractive force between H connected to an electronegative atom and a lone pair of e- on N, O, or F. London Forces...
by Alan Wu
Fri Nov 08, 2019 6:44 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: Hydrogen bonding in DNA
Replies: 2
Views: 11

Re: Hydrogen bonding in DNA

Wait are you sure? Because in class we learned that there are 3 pairs of hydrogen bonds between G and C compared to 2 pairs between A and T. Therefore, G and C are harder to break apart.
by Alan Wu
Fri Nov 08, 2019 6:43 pm
Forum: *Liquid Structure (Viscosity, Surface Tension, Liquid Crystals, Ionic Liquids)
Topic: Bonds vs Shapes [ENDORSED]
Replies: 4
Views: 253

Re: Bonds vs Shapes [ENDORSED]

Usually viscosity or any property in liquid/solid form is determined by the intermolecular forces between the individual molecules. In that case, single bonds and double bonds don't apply to intermolecular forces. We learned in class that having a rod shape compared to a spherical shape greatly incr...
by Alan Wu
Fri Nov 01, 2019 6:06 pm
Forum: Dipole Moments
Topic: How to draw the dipole moment
Replies: 2
Views: 53

Re: How to draw the dipole moment

Point the arrow toward the more negative region. You can also put a + on the arrow at the more positive side.
by Alan Wu
Fri Nov 01, 2019 6:04 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizability and Electronegativity
Replies: 2
Views: 19

Re: Polarizability and Electronegativity

Polarizability, or polarizing power depends solely on the anion's electronegativity. I is bigger and less electronegative than the other halogens, so it has a greater polarizability. Polarizing power, on the other hand, is determined by the cation's charge and size. These are separate things.
by Alan Wu
Fri Nov 01, 2019 6:00 pm
Forum: Coordinate Covalent Bonds
Topic: Difference between coordinate covalent and covalent bond
Replies: 6
Views: 547

Re: Difference between coordinate covalent and covalent bond

An example of a covalent bond would simply be F + F --> F2. In this molecule, each F donates one electron to share with the other. An example of a coordinate covalent bond would be BF3 + F- --> BF4. In this molecule, F- provides 2 electrons to share with the central atom B and to complete its octet....
by Alan Wu
Fri Nov 01, 2019 5:56 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Memorizing the Equation
Replies: 4
Views: 60

Re: Memorizing the Equation

Formal charge for an atom = # of valence electrons - (# of lone electrons + # of bonds)

This should be easier than counting the number of shared electrons and the dividing it by 2. Just count the number of bonds that atom has in the lewis structure instead.
by Alan Wu
Fri Nov 01, 2019 5:50 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charges
Replies: 4
Views: 25

Re: Formal Charges

In a resonance structure, the formal charges for same atoms should all be equal in reality. This is because in reality, the structure is a hybrid of all the resonance structures. For example, in the SO4 2- resonance structures with 2 Os connected to S with double bonds and 2 Os connected to S with s...
by Alan Wu
Fri Nov 01, 2019 5:45 pm
Forum: Ionic & Covalent Bonds
Topic: Distorted e- with Ionic Bonds
Replies: 5
Views: 31

Re: Distorted e- with Ionic Bonds

A perfect, complete, 100% ionic bond would mean that the cation has lost its valence electrons completely and the anion has gained those electrons completely. In a 100% ionic bond, there should be no electrons entering the cation's electron cloud. However, the cation having a positive charge, tends ...
by Alan Wu
Fri Nov 01, 2019 5:41 pm
Forum: Ionic & Covalent Bonds
Topic: How does one find a most likely charge for ions for a given element?
Replies: 6
Views: 39

Re: How does one find a most likely charge for ions for a given element?

Another way to determine the most likely charge for an ion of a given element is to look at that element's successive ionization energies. For example, Mg's 1st IE = 737.7 KJ/mol, 2nd IE = 1450.6 KJ/mol, and 3rd IE = 7732.6 KJ/mol. The huge increase from the second to third IE for Mg means that afte...
by Alan Wu
Fri Oct 25, 2019 5:46 pm
Forum: Ionic & Covalent Bonds
Topic: Identifying Ionic vs Covalent
Replies: 7
Views: 51

Re: Identifying Ionic vs Covalent

Difference in electronegativity:
0.0 - 0.4: non-polar covalent bond
0.4 - 1.8: polar covalent bond
>1.8: ionic bond

These numbers can vary from source to source, but you get the general idea.
by Alan Wu
Fri Oct 25, 2019 5:43 pm
Forum: Sigma & Pi Bonds
Topic: Significance of Sigma and Pi Bonds
Replies: 3
Views: 33

Significance of Sigma and Pi Bonds

What is the significance of sigma and pi bonds? How do they affect the properties of a compound?
by Alan Wu
Fri Oct 25, 2019 5:40 pm
Forum: Trends in The Periodic Table
Topic: Summary of Periodic Trends
Replies: 7
Views: 68

Re: Summary of Periodic Trends

Is electron affinity only important/ only affects Group 17 (according to Lavelle) and noble gases? Or why is it important to know the electron affinity? It's important to know the electron affinity of elements probably because we can use that to measure how much energy is released or gained in reac...
by Alan Wu
Fri Oct 25, 2019 5:33 pm
Forum: Trends in The Periodic Table
Topic: Electron Affinity
Replies: 4
Views: 18

Electron Affinity

Why is electron affinity negative in some textbooks and positive in this one? I learned in high school that if energy is released when an electron is added to an atom, it should be represented by a negative value. So are the positive values of electron affinity in this book just the direct opposite ...
by Alan Wu
Fri Oct 25, 2019 5:30 pm
Forum: Trends in The Periodic Table
Topic: Electronegativity
Replies: 3
Views: 24

Re: Electronegativity

The atoms of elements toward the right of a period (except for the noble gases) are more electronegative because they have more protons and the same amount of shielding compared to the other elements in the same period. Therefore, their nuclear charge is higher and it's easier for them to pull an el...
by Alan Wu
Fri Oct 18, 2019 6:08 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Hund's Rule
Replies: 3
Views: 19

Re: Hund's Rule

This is all a result of electron repulsion. Since electrons are all negatively charged, they repel each other and would want to occupy separate orbitals (they are farther from each other that way).
by Alan Wu
Fri Oct 18, 2019 6:04 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Noble Gas Shortcut
Replies: 3
Views: 25

Re: Noble Gas Shortcut

I don't think you can just write [Ar] for Argon. You won't be writing any actual configuration then. I'm pretty sure for noble gases, you have to use the previous one and write out all the valence electrons.
by Alan Wu
Fri Oct 18, 2019 6:02 pm
Forum: Trends in The Periodic Table
Topic: calculating the state
Replies: 3
Views: 32

Re: calculating the state

These Px, Py, and Pz states are not associated with any of the magnetic quantum numbers (-1,0,1) for the p subshell, unless otherwise stated. Electrons in reality can fill in these orbitals in any order; Px, Py, and Pz are just the names we give these orbitals.
by Alan Wu
Fri Oct 18, 2019 6:00 pm
Forum: Trends in The Periodic Table
Topic: Exceptions in Periodic Trends
Replies: 2
Views: 48

Exceptions in Periodic Trends

I remember there were exceptions in periodic trends in ionization energy and something else. They are due to penetration of the s-orbital over the p-orbital and Hund's Rule. May someone please give a recap on these exceptions?
by Alan Wu
Fri Oct 18, 2019 5:56 pm
Forum: *Shrodinger Equation
Topic: Wave Function and Orbitals
Replies: 3
Views: 33

Wave Function and Orbitals

How exactly does Schrodinger's Wave Function equation relate to the orbitals (1s, 2s, 2p... etc.)? I know the orbitals are solutions to the Wave Function, but what exactly does that mean? Like do the orbitals have energies corresponding to the ones calculated by this equation?
by Alan Wu
Fri Oct 11, 2019 5:53 pm
Forum: Photoelectric Effect
Topic: Wavelengths?
Replies: 8
Views: 56

Re: Wavelengths?

Amplitude, or intensity, for waves are measured by the height of the waves from their base to their peak. However, if light is regarded as a photon, amplitude, or intensity, is simply the number of photon particles emitted. That's why light with higher intensity resulted in more electron emissions b...
by Alan Wu
Fri Oct 11, 2019 5:48 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Types of E
Replies: 3
Views: 49

Re: Types of E

E(photon) = hv, whereas Ek or E(electron) = 1/2 mv^2

E(photon) = threshold energy + Ek
by Alan Wu
Fri Oct 11, 2019 5:44 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Negative Energy Value for Hydrogen Energy Levels
Replies: 2
Views: 18

Negative Energy Value for Hydrogen Energy Levels

Can someone explain why electrons bound to the various energy levels of hydrogen have negative energies as calculated by Rydberg's equation?
by Alan Wu
Fri Oct 11, 2019 5:40 pm
Forum: Properties of Electrons
Topic: Ionization energy
Replies: 4
Views: 39

Re: Ionization energy

This may not be the best way to explain it, but it can help you understand this phenomenon better. Elements toward the left of each period have less valence electrons and are more likely to lose them to establish a stable octet. For example, Na only needs to get rid of one electron to achieve a stab...
by Alan Wu
Fri Oct 11, 2019 5:36 pm
Forum: Properties of Light
Topic: Frequency and Hertz
Replies: 5
Views: 47

Re: Frequency and Hertz

I believe for the sake of this class, there's no need to break down the unit for hertz. It's simply s^-1 and that works perfectly in equations such as E=hv because it cancels out with Planck's constant to get the final answer in Joules.
by Alan Wu
Fri Oct 04, 2019 6:21 pm
Forum: Photoelectric Effect
Topic: photoelectric effect
Replies: 2
Views: 50

Re: photoelectric effect

The answer is D.

Simply use the equation E=hv to solve this.

E = 6.63x10^-34 JS * 3.00x10^15 Hz = 1.99x10^-18 J
by Alan Wu
Fri Oct 04, 2019 6:18 pm
Forum: Einstein Equation
Topic: Planack's constant
Replies: 8
Views: 95

Re: Planack's constant

Placnk's constant is used to find the energy of a photon given its frequency or wavelength.

These 2 equations are very handy:
Energy of photon = planck's constant (h) * frequency
Energy of photon = planck's constant (h) * (speed of light (c) / wavelength)
by Alan Wu
Fri Oct 04, 2019 6:15 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Absorption Spectrum
Replies: 2
Views: 52

Absorption Spectrum

I don't get why only EMs of specific wavelengths can be absorbed by Hydrogen atoms. I understand that the Emission Spectrum is a result of electrons falling back from one specific energy level to another. However, why can only specific wavelengths be absorbed? If the EM has a short wavelength and th...
by Alan Wu
Fri Oct 04, 2019 6:11 pm
Forum: Trends in The Periodic Table
Topic: Effective Nuclear Charge
Replies: 1
Views: 37

Effective Nuclear Charge

How would we calculate Zeff in this class? Do we subtract the number of shielding electrons from the atomic number Z? Or do we need to know Slater's Rule? If that's the case, can someone please explain Slater's Rule?
by Alan Wu
Fri Oct 04, 2019 6:07 pm
Forum: *Black Body Radiation
Topic: Wavelength and Temperature
Replies: 2
Views: 34

Wavelength and Temperature

1B.11 The star Antares emits light with maximum intensity at 850 nm. What is the temperature at the surface of Antares?

What is the relationship between wavelength and temperature? Can someone explain the equation needed to solve this question?
by Alan Wu
Sat Sep 28, 2019 4:50 pm
Forum: Molarity, Solutions, Dilutions
Topic: Dilution
Replies: 9
Views: 128

Re: Dilution

When dilution occurs, you are only adding water (or solvent) to the solution. Whatever the solute is remains unchanged in amount. Only solvent has been added. Therefore, the moles of solute remains the same prior to and after dilution. This means that M1V1 = M2V2, and by knowing 3 of those values, y...
by Alan Wu
Sat Sep 28, 2019 4:40 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Avogradro's Number [ENDORSED]
Replies: 5
Views: 123

Re: Avogradro's Number [ENDORSED]

1 mole just means 6.022 * 10^23 number of things. It is just like how you would say I have a dozen eggs, where dozen refers to "12". You can have 1 mole of atoms, 1 mole of eggs, or in this case, 1 mole of humans. For this question, to find how many moles of humans there are on Earth, simp...
by Alan Wu
Sat Sep 28, 2019 4:37 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Figuring out the names of things
Replies: 4
Views: 95

Re: Figuring out the names of things

Since tin can have multiple charges, SnO2 must be named as Tin (II) Oxide. This is how you name any ionic compound in which the metal can have multiple charges. Whereas an element like magnesium with only one possible charge (2+) would combine with oxygen to form magnesium oxide.
by Alan Wu
Sat Sep 28, 2019 4:32 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Formula Unit
Replies: 7
Views: 86

Re: Formula Unit

Formula units are typically used to describe one unit of an ionic compound. Ionic compounds are often found in huge lattice structures, where the positive and negative ions alternate. The formula unit would describe the most basic unit that makes up the ionic compound (e.g. NaCl). A molecule is used...
by Alan Wu
Sat Sep 28, 2019 4:29 pm
Forum: Empirical & Molecular Formulas
Topic: Empirical Formulas Rounding and Multiplying
Replies: 11
Views: 130

Re: Empirical Formulas Rounding and Multiplying

Another thing you should remember to do is to not round intermediate answers to the desired sig figs. Directly take whatever number you got from your calculator and copy it onto the next line to perform the calculation. Many often round the intermediate answers and that could result in undesirable f...

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