Search found 66 matches
- Sun Mar 17, 2019 1:58 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Effects of Compression
- Replies: 5
- Views: 583
Re: Effects of Compression
Yes compression would effect the position of a reaction, taking it away from equilibrium. When the volume reduces, the side that has less gas molecules is favored. The compression increases pressure because of the gaseous state.
- Sun Mar 17, 2019 1:56 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Le Chatelier's Principle
- Replies: 6
- Views: 629
Re: Le Chatelier's Principle
When the concentration of reactants increases, forward reaction is favored (vice versa)
When the temperature increases for an endothermic reaction, forward reaction is favored (vice versa)
When gas is compressed, the side that has less gas molecules will be favored
When the temperature increases for an endothermic reaction, forward reaction is favored (vice versa)
When gas is compressed, the side that has less gas molecules will be favored
- Sun Mar 17, 2019 1:55 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: When is delta U = 0?
- Replies: 4
- Views: 794
Re: When is delta U = 0?
For an isothermal system delta U = 0
- Sun Mar 17, 2019 1:53 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2986410
Re: Post All Chemistry Jokes Here
If the Silver Surfer and Iron Man team up, they’d be alloys.
- Sun Mar 17, 2019 1:52 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2986410
Re: Post All Chemistry Jokes Here
Q: What is the chemical formula for "coffee"?
A: CoFe2
A: CoFe2
- Sun Mar 17, 2019 1:52 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2986410
Re: Post All Chemistry Jokes Here
Why do chemists like nitrates so much?
They're cheaper than day rates.
They're cheaper than day rates.
- Sun Mar 17, 2019 1:52 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2986410
Re: Post All Chemistry Jokes Here
Did you know that you can cool yourself to -273.15˚C and still be 0K?
yikes that wasn't such hot joke.
yikes that wasn't such hot joke.
- Sun Mar 17, 2019 1:51 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2986410
Re: Post All Chemistry Jokes Here
Why can't you trust atoms?
They make up everything haha
They make up everything haha
- Sun Mar 17, 2019 1:49 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Largest E Cell
- Replies: 2
- Views: 694
Re: Largest E Cell
You would subtract the most positive reduction potential from the most negative reduction potential.
- Sun Mar 17, 2019 1:48 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: adding an inert gas
- Replies: 4
- Views: 627
Re: adding an inert gas
They are unreactive!
- Sun Mar 17, 2019 1:48 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: What is pKa and Ka exactly?
- Replies: 16
- Views: 24766
Re: What is pKa and Ka exactly?
Ka is acid dissociation constant and represents the strength of the acid. pKa is the -log of Ka, having a smaller comparable values for analysis. They have an inverse relationship. Larger the Ka, smaller the pKa and stronger the acid.
- Sun Mar 17, 2019 1:41 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Increasing volume
- Replies: 5
- Views: 723
Re: Increasing volume
Yes if the volume increases K will indicate movement to whichever side has less gas molecules, this is because an increase in volume (expansion) is indicative of a decrease in pressure.
- Sun Mar 17, 2019 1:40 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Pt
- Replies: 2
- Views: 494
Re: Pt
Platinum is an inert element the is used as an electrode for whichever side lacks a solid
- Sun Mar 17, 2019 1:34 am
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Pre-equilibrium Approach
- Replies: 2
- Views: 608
Re: Pre-equilibrium Approach
For K, we only consider the aqueous and gaseous states, and ignore the liquids and solids
- Sun Mar 17, 2019 1:33 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagram
- Replies: 2
- Views: 475
Cell Diagram
If H+(aq) is added in the half equation, how do you know where to put it for the cell diagram?
- Sun Mar 17, 2019 1:28 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Exothermic vs. Endothermic
- Replies: 10
- Views: 1831
Re: Exothermic vs. Endothermic
Both endothermic and exothermic reactions have Ea, however endothermic reactions will have a larger energy barrier to go over.
- Sun Mar 17, 2019 1:26 am
- Forum: General Rate Laws
- Topic: Rate constant units
- Replies: 3
- Views: 659
Re: Rate constant units
The units for rate are mol.L-1.s-1, change of concentration over change in time. The rate constant units depend on the order of the reaction. To put it simply, a 0th order k: mol.L-1.s-1, 1st order k: s-1, 2nd order k: mol-1.L.s-1
- Sun Mar 17, 2019 1:24 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: catalyst vs intermediate
- Replies: 3
- Views: 626
Re: catalyst vs intermediate
Catalysts are there from the beginning, but are never consumed. However, intermediates are formed and consumed within the reaction.
- Sun Mar 17, 2019 1:23 am
- Forum: Ideal Gases
- Topic: ICE table
- Replies: 7
- Views: 829
Re: ICE table
Ka is [A-][H+]/[HA], so if you have the initial concentration of HA you'll be able to calculate the concentration of hydrogen ions.
- Sun Mar 17, 2019 1:20 am
- Forum: Balancing Redox Reactions
- Topic: Balanced Half Reactions
- Replies: 5
- Views: 670
Re: Balanced Half Reactions
you will need to balance the number of ions and electrons for each half reaction and then to combine them and get an overall reaction you will need to balance both half equations to have the same number of electrons.
- Sun Mar 17, 2019 1:13 am
- Forum: Second Order Reactions
- Topic: 6th edition 15.39
- Replies: 2
- Views: 550
Re: 6th edition 15.39
the rate law isn't directly related to the coefficients of the reactants
- Sun Mar 17, 2019 1:03 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Adiabatic and isothermal
- Replies: 6
- Views: 2240
Re: Adiabatic and isothermal
An adiabatic process occurs without transfer of heat or mass of substances between a thermodynamic system and its surroundings. In an adiabatic process, energy is transferred to the surroundings only as work. An isothermal process is a change of a system, in which the temperature remains constant: Δ...
- Sun Mar 17, 2019 1:01 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst Equation Confusion
- Replies: 4
- Views: 734
Re: Nernst Equation Confusion
They are the same, however the second equation is commonly used in questions that ask for pH to be found from the [H+]
- Sun Mar 17, 2019 1:00 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: pseudo rate law
- Replies: 7
- Views: 1047
Re: pseudo rate law
So the pseudo rate law just allows easier analysis of the effect of one reactant. In this case, the other reactant(s) are in high concentration that they can be considered constant, and so k[high conc. reactant] is k'
- Sun Mar 17, 2019 12:58 am
- Forum: *Enzyme Kinetics
- Topic: Adsorption
- Replies: 13
- Views: 3099
Re: Adsorption
Adsorption occurs with a heterogeneous catalyst, it provides a solid surface area for compounds to react.
- Sun Mar 17, 2019 12:57 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Units of k
- Replies: 5
- Views: 904
Re: Units of k
we know that the units for rate are mol.L-1.s-1 Zero order: rate =k[A]^0 so units of k have to be the same as the units for the rate First order: rate =k[A] the multiplication of the units of k and units of concentration of A (i.e mol.L-1) should result in the units for the rate; thus, units of k is...
- Sun Mar 17, 2019 12:54 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: cell concentration
- Replies: 1
- Views: 463
Re: cell concentration
Did you mean to upload a picture for this question?
- Sun Mar 17, 2019 12:50 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: chemical to electrical
- Replies: 2
- Views: 549
Re: chemical to electrical
Galvanic cell!
- Sun Mar 17, 2019 12:49 am
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: molar mass
- Replies: 3
- Views: 3715
Re: molar mass
It would depend on what formula and variables you have to calculate the entropy.
- Sun Mar 17, 2019 12:35 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: first law
- Replies: 2
- Views: 438
Re: first law
The first law states that in an isolated system, there is no change in internal energy. So w=-q.
- Sun Mar 17, 2019 12:34 am
- Forum: Balancing Redox Reactions
- Topic: balaning redox reactions
- Replies: 3
- Views: 587
Re: balaning redox reactions
In the example of 2Fe^2+, a reduction reaction would look like:
2Fe^2+ + 4e- ---> 2Fe
I hope this answered your question!
2Fe^2+ + 4e- ---> 2Fe
I hope this answered your question!
- Sun Mar 17, 2019 12:32 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Units k
- Replies: 3
- Views: 611
Re: Units k
This would depend on the order of the reaction! It's easiest to write out the units for each individual element of the rate law and cancel out units from there. Here's a short cut though: first order: s^-1, second: mol^-1.L.s^-1, third: mol^-2.l^2.s^-1
- Mon Jun 11, 2018 2:11 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2986410
Re: Post All Chemistry Jokes Here
Q: Did you hear oxygen went on a date with potassium?
A: It went OK
A: It went OK
- Mon Jun 11, 2018 2:11 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2986410
Re: Post All Chemistry Jokes Here
Why do chemists like nitrates so much?
They're cheaper than day rates.
They're cheaper than day rates.
- Sat Jun 09, 2018 4:36 pm
- Forum: Bronsted Acids & Bases
- Topic: J.5
- Replies: 2
- Views: 456
Re: J.5
^^ you'd have to know that non-metals create acids, most metals form bases and i think you'll have to remember the middle section of amphoteric elements.
- Sat Jun 09, 2018 4:34 pm
- Forum: Empirical & Molecular Formulas
- Topic: Empirical to molecular
- Replies: 3
- Views: 4137
Re: Empirical to molecular
calculate what the molar mass of the empirical formula is, let's call this 'x'. The question, more often than not, will provide you with the actual molar mass of the compound ('y'). Divide 'y' by 'x', this will give you the ratio of empirical formula to molecular. Using the whole number obtained, mu...
- Sat Jun 09, 2018 4:28 pm
- Forum: Dipole Moments
- Topic: Are London dispersion forces present in every molecule?
- Replies: 2
- Views: 464
Re: Are London dispersion forces present in every molecule?
London dispersion forces are present between any 2 molecules that are close together
- Sat Jun 09, 2018 4:26 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Oxidation Number
- Replies: 5
- Views: 878
Re: Oxidation Number
The oxidation number of a free element is always 0. The oxidation number of a monatomic ion equals the charge of the ion.
- Wed Jun 06, 2018 9:16 pm
- Forum: Conjugate Acids & Bases
- Topic: pKa [ENDORSED]
- Replies: 3
- Views: 592
Re: pKa [ENDORSED]
You will need to find the concentration of products (ions) and the initial acid through experimentation (when mixed with water). In this case, pH is often equal to pKa. The general equation would be: [+ion][-ion]/[acid]
- Wed Jun 06, 2018 9:10 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2986410
Re: Post All Chemistry Jokes Here
What do dipoles say in passing?
Have you got a moment?
Have you got a moment?
- Wed Jun 06, 2018 9:06 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2986410
Re: Post All Chemistry Jokes Here
You'd think that atoms bonding with other atoms would mean they're being friendly, but really they steal each other's electrons.
How ionic.
How ionic.
- Wed Jun 06, 2018 9:03 pm
- Forum: Hybridization
- Topic: Pi bonds in triple bond
- Replies: 17
- Views: 1755
Re: Pi bonds in triple bond
There are 2 pi bonds in a triple bond and 1 pi bond in a double bond.
- Wed Jun 06, 2018 3:54 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polar VS Nonpolar shapes
- Replies: 4
- Views: 563
Re: Polar VS Nonpolar shapes
The dipole moments have to be equal in strength, so 2 of the same bonds can cancel each other out. "Cancel" here means opposing vectors. However, when you're considering whether a compound is polar or nonpolar always think of the structure in 3D.
- Wed Jun 06, 2018 3:38 pm
- Forum: Electronegativity
- Topic: HW question 3.77
- Replies: 4
- Views: 855
Re: HW question 3.77
The electronegativity difference between C and H is less than the difference between C and F. C and H have almost the same electronegativity.
- Sat Jun 02, 2018 2:01 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2986410
Re: Post All Chemistry Jokes Here
Initially I decided to write jokes about the Periodic Table, but never really felt I was in my element.
- Wed May 30, 2018 5:10 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: lone pairs
- Replies: 5
- Views: 739
Re: lone pairs
Commonly, a linear compound consists of 3 atoms that lie at 180 degrees. The compound takes a bent structure when there is a lone pair found on the central atom (usually on top). This creates a repelling force that pushes both the present bonds downwards into a 120 degree angle.
- Wed May 30, 2018 4:16 pm
- Forum: Ionic & Covalent Bonds
- Topic: Double/Triple Bonds
- Replies: 8
- Views: 1007
Re: Double/Triple Bonds
most atoms are capable of having double or triple bonds. It's just a matter of oxidation states and formal charges in order to create the most stable structure of the compound. They are usually added to complete the octet of atoms.
- Wed May 30, 2018 4:02 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond angles and lone pairs
- Replies: 4
- Views: 733
Re: Bond angles and lone pairs
if you are given just the bond angle and number of atoms involved, you'll know a lone pair is involved when the bond angle is smaller than usual. this is because lone pairs repel the bonded pairs, causing the angle to be smaller.
- Wed May 30, 2018 3:37 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR confusion
- Replies: 8
- Views: 1271
Re: VSEPR confusion
^^ Valence shell electron pair repulsion (VSEPR) theory is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. The VSEPR formula is just the structure.
- Wed May 30, 2018 3:33 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2986410
Re: Post All Chemistry Jokes Here
Q: How often does this group tell chemistry jokes?
A: Periodically!
A: Periodically!
- Wed May 30, 2018 3:29 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Cancelling out dipole moments
- Replies: 3
- Views: 989
Re: Cancelling out dipole moments
Once you draw out the compound, the biggest thing that will help you are the dipole arrows in relation to the elements involved. If you have an asymmetrical structure that's one sign but when deciding if something is polar or nonpolar check if the arrows of 2 identical bonds cancel out (are exactly ...
- Mon May 14, 2018 6:57 pm
- Forum: Significant Figures
- Topic: what part of the probem to apply sig fig rules
- Replies: 2
- Views: 424
Re: what part of the probem to apply sig fig rules
It's best not to round off any values used in the calculation. Only apply the sig fig rule to your final answer. This will give you the most accurate value!
- Sun May 13, 2018 5:22 pm
- Forum: Properties of Light
- Topic: Test 2 Question 4
- Replies: 8
- Views: 884
Re: Test 2 Question 4
Most students attempted to solve this problem using Rydberg's, however that is not necessary. The question already mentions that energy is released in the form of light at 400nm. The energy produced by this wavelength is the "energy difference". So all we need is to plug in the wave length...
- Sun May 13, 2018 5:18 pm
- Forum: Lewis Structures
- Topic: Expanded Octet
- Replies: 2
- Views: 633
Re: Expanded Octet
These elements are capable of forming expanded octets (some more often than others), but you will not always find the elements in that state. For instance, compare Sulfur oxide (SO2) to sulfur hexafluoride (SF6).
- Sun May 13, 2018 5:15 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Calculating formal charges
- Replies: 5
- Views: 1055
Re: Calculating formal charges
To calculate the formal charge, subtract the sum of the total number of lone electrons and total number of bonds (0.5 x total number of bonded electrons) from the number of valence electrons of that specific atom. All the atoms FC should add up to the compounds overall charge. It is preferred to hav...
- Sun May 13, 2018 5:10 pm
- Forum: Lewis Structures
- Topic: BrO- Lewis Structure
- Replies: 4
- Views: 1814
Re: BrO- Lewis Structure
Hypobromite ion would have one covalent bond between the Br and O atoms. Both atoms would have complete octets but the oxygen atom would have a -1 charge due to an extra electron.
- Sat May 12, 2018 5:52 pm
- Forum: Ionic & Covalent Bonds
- Topic: HW problem 3.21
- Replies: 4
- Views: 1310
Re: HW problem 3.21
The answer key is right; the ground state electron configuration for Ag+ is [kr] 4d^10 and has no unpaired electrons. The ground state electron configuration for just Ag is [kr] 4d^10 5s^1. Since Ag+ has a charge of +1, that means it is losing an electron to become more positive. Since 5s has a high...
- Sat May 12, 2018 5:43 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal charges and full valence shells
- Replies: 3
- Views: 630
Re: Formal charges and full valence shells
There's no direct relationship between formal charges and full valence shells. Full valence shells do no always result in a formal charge of zero, they can result in formal charges of -1,+1 and others. The formal charge is calculated by subtracting the sum of the number of lone pair electrons and th...
- Sat May 12, 2018 5:36 pm
- Forum: Ionic & Covalent Bonds
- Topic: Why can't hydrogen be a central atom? [ENDORSED]
- Replies: 6
- Views: 3752
Re: Why can't hydrogen be a central atom? [ENDORSED]
Hydrogen can't be the central atom because it can only form one bond, so it must generally be in the outer layer of atoms. When drawing a lewis structure, it's recommended for hydrogen atoms to be added in last.
- Sat May 12, 2018 5:31 pm
- Forum: Ionic & Covalent Bonds
- Topic: Nonpolar covalent bonds
- Replies: 2
- Views: 347
Re: Nonpolar covalent bonds
A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. Lewis structures are often used to depict the sharing of electrons between atoms in a covalently bonded compound.
- Wed Apr 18, 2018 9:08 pm
- Forum: Empirical & Molecular Formulas
- Topic: empirical vs molecular
- Replies: 5
- Views: 686
Re: empirical vs molecular
The empirical formula is the most simplified version of the formula, with the smallest ratio of whole numbers. So if glucose C6H1206 was divided by 3, we would get CH2O which is that most simplified formula. The molecular accounts for the actual state of the compound and its atomic binding.
- Wed Apr 18, 2018 9:06 pm
- Forum: Limiting Reactant Calculations
- Topic: Limiting Reactants
- Replies: 5
- Views: 549
Re: Limiting Reactants
If you want to find the limiting reactant of this question, you would first need to calculate the number of moles present of each reactant (by using the molar mass and given mass). Then use the ratio of 1 mole of CaC2: 2 moles of H2O to deduce which of the reactants is actually present in excess.
- Wed Apr 18, 2018 9:03 pm
- Forum: Significant Figures
- Topic: Rounding: when and where?
- Replies: 10
- Views: 837
Re: Rounding: when and where?
As mentioned above, don't round off until the final answer. Your answer would not be marked as wrong but maybe to be safe in parenthesis mention that number of sig figs you've rounded to. However, the general rule is round off to the lowest number of sig figs given in the question asked.
- Wed Apr 18, 2018 8:59 pm
- Forum: DeBroglie Equation
- Topic: 10^-18
- Replies: 3
- Views: 427
Re: 10^-18
As Jack said, the EMS has currently identified wavelengths between the range of 10^(-18) to approximately 100 km. Since the smallest identifiable wavelength is to the 10^-18 (gamma waves), anything smaller than that is undetectable. The car mentioned in class would be considered a classical particle...
- Wed Apr 18, 2018 8:55 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Frequency if energy goes from n=2 to n=4
- Replies: 6
- Views: 560
Re: Frequency if energy goes from n=2 to n=4
When you go from a lower energy level to a higher level, energy is require. The electron absorbs this energy, over releasing a photon. So as mentioned, photons will not have a negative value of energy. However, the change in energy of the electron will be positive going up energy levels and negative...
- Wed Apr 18, 2018 8:49 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: The Negative Sign in En = -hR/n^2
- Replies: 5
- Views: 588
Re: The Negative Sign in En = -hR/n^2
That is correct. The energized electron falls from a higher energy level to a lower energy level (releasing photons). The release of energy causes the change in energy (Delta E) to be a negative value.