## Search found 20 matches

Fri Mar 11, 2016 11:26 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Practice Final 2011, Q1C
Replies: 2
Views: 373

### Re: Practice Final 2011, Q1C

Ethane has a carbon carbon single bond, unlike ethene which has a double bond. The single bond also allows for greater conformational complexity, or a greater number of possible states.
Fri Mar 11, 2016 12:23 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Final exam 2015 #1c Enthalpy with heat and mass
Replies: 3
Views: 468

### Re: Final exam 2015 #1c Enthalpy with heat and mass

The units for the enthalpy of fusion are usually kJ/mol but this problem specifically asks for it in kJ/g. 390 kJ is the amount of heat required to melt the 15.9 gram ring, but since you want to find how much heat is needed to melt just 1 gram, you would divide 390 kJ by 15.9 grams.
Fri Mar 04, 2016 10:21 pm
Forum: *Alkanes
Topic: Halogen substituents
Replies: 3
Views: 418

### Re: Halogen substituents

On the first practice quiz, number 5 is a cyclohexane with I and Br as substituents. With 2 different possible ways of counting, either I or Br could be counted as 1 or 3. The answer, however, is 3-bromo-1-iodocyclohexane. I assume that it's because I has a larger atomic number than Br does that I i...
Fri Feb 26, 2016 3:57 pm
Forum: *Electrophiles
Topic: Nucleophiles
Replies: 5
Views: 624

### Re: Nucleophiles

Nucleophilic strength decreases going across a period.
e.g. R3C- > R2N- >RO- > F-

It increases going down a group, due to the polarizability effect.
e.g. F- < Cl- < Br- < I-
Sun Feb 21, 2016 5:43 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: order
Replies: 3
Views: 529

### Re: order

Here are the units of rate constant k for each order:

first order: s^-1
second order: L. mol^-1 s^-1 (or M^-1 s^-1)
zero order: mol. L^-1 s^-1
Sun Feb 14, 2016 12:28 am
Forum: Balancing Redox Reactions
Topic: General Redox Reactions
Replies: 2
Views: 337

### Re: General Redox Reactions

You would include H2O in the redox equation but not in the cell diagram for it.
Sat Feb 06, 2016 5:57 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 2013 Midterm 3a
Replies: 1
Views: 326

### Re: 2013 Midterm 3a

As given by the formula list, the enthalpy of vaporization for water is 40.7 kJ/mol, or 40700 J/mol. To find the enthalpy of vaporization per gram of water, you divide 40700 J by 18.016 g, the molar mass of water. You get 2259 J/g, which is the number that the problem uses in the solution given.
Sat Jan 30, 2016 8:22 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Endothermic or exothermic
Replies: 3
Views: 376

### Re: Endothermic or exothermic

Heat is needed to break bonds, so the reaction must be endothermic. In contrast, heat is released when bonds are formed because the products are at a more stable state and have less enthalpy than the reactants, making the reaction exothermic instead.
Fri Jan 22, 2016 9:51 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Relationship Between Degeneracy and Entropy
Replies: 1
Views: 278

### Re: Relationship Between Degeneracy and Entropy

Entropy can be seen as the a measure of the randomness of a system, as the system can be in one of multiple possible states. Relating to this, degeneracy (W) is the number of ways in which a given energy state can be achieved. In other words, it is the number of possible microstates, which all have ...
Sat Jan 16, 2016 4:01 pm
Forum: Phase Changes & Related Calculations
Topic: delta U
Replies: 2
Views: 908

### Re: delta U

As previously stated, the internal energy of a system changes when work is done and heat is absorbed or released as enthalpy (i.e. delta H). If the reaction occurs at constant pressure, delta U is equal to delta H. For an isolated system, however, delta U must be 0 according to the first law of ther...
Fri Jan 08, 2016 11:10 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat vs. Specific Heat Capacity
Replies: 4
Views: 1814

### Re: Heat vs. Specific Heat Capacity

Since heat capacity is an extensive property, specific heat capacity is an intensive property. To get a better idea of what an intensive property is, think about density, for example. Density is an intensive property because it is the ratio between the mass of the solute and the volume of the soluti...
Fri Dec 04, 2015 7:25 pm
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: HomeworkQuestion 13.11 part b
Replies: 1
Views: 275

### Re: HomeworkQuestion 13.11 part b

The 1.00 x 10^-2 mol of acetic acid is from the initial concentration of acetic acid, 0.100 M acetic acid in a solution with a volume of 100 mL. It is added to the 2.00 x 10^-3 mol of acetic acid made with the addition of the HNO3. From there, you can calculate the concentrations of acetic acid and ...
Sat Nov 28, 2015 12:59 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Electronegativity and acid strength
Replies: 4
Views: 5309

### Re: Electronegativity and acid strength

If A is more electronegative, the bond in HA is also more polar. The H atom will have a greater partial positive charge, which creates a stronger hydrogen bond between the H atom and the O atom of the H2O molecule. Because it is then easier for the proton, H, to be transferred, HA is a stronger acid.
Fri Nov 20, 2015 8:19 pm
Forum: Naming
Topic: -ate ending
Replies: 2
Views: 520

### Re: -ate ending

The ending -ate is added to the metal if the complex itself, which is everything that is inside the brackets, has a negative charge. [CoF6] has a charge of -3 when cobalt has the oxidation state of 3. K3, the cation, has a charge of 3 which then makes the entire compound neutral.
Fri Nov 13, 2015 5:32 pm
Forum: Naming
Topic: Aqua or Hydrate
Replies: 2
Views: 421

### Re: Aqua or Hydrate

In that example, H20 functions as a ligand. When it is a ligand, it is named aqua.
Fri Nov 06, 2015 9:01 pm
Forum: Bond Lengths & Energies
Topic: Bond Order Meaning
Replies: 3
Views: 6657

### Re: Bond Order Meaning

A bond order of 1.5 would mean that there are resonance structures, as a resonance hybrid would result from the blending of two or more possible Lewis structures for the molecule or ion. The average of the bonds in each structure could result in a number like 1.5. In addition, bond order can also te...
Sat Oct 31, 2015 12:39 pm
Forum: Hybridization
Topic: How to Determine Electron Density
Replies: 4
Views: 2011

### Re: How to Determine Electron Density

Also, a bond is counted as a single region of electron density regardless of whether it is a single, double, or triple bond. For example, the Lewis Structure of phosphate (PO4^3-) shows it to have 3 single bonds and a double bond. There are 4 regions of electron density.
Fri Oct 23, 2015 10:42 pm
Forum: Lewis Structures
Topic: Lewis structure
Replies: 3
Views: 629

### Re: Lewis structure

Calculating formal charge would also help determine where to use which bonds, since it takes into consideration the number of lone and shared electrons of an atom. A formal charge of 0 is sought after since it would mean that an atom is stable.
Sat Oct 17, 2015 2:49 pm
Forum: Properties of Light
Topic: Conversions
Replies: 2
Views: 401

### Re: Conversions

You would multiply that number by 2 to have the entire amount of uncertainty in the speed of the object.
Sat Oct 10, 2015 12:15 pm
Forum: SI Units, Unit Conversions
Topic: Quiz 1 Preparation
Replies: 2
Views: 509

### Re: Quiz 1 Preparation

Adding on to Marla's explanation, here are the steps outlined! To find the amount of moles of solute (NaOH), you can use the formula: molarity (M) = moles of solute (n) / volume of solution (v) 2.00 M NaOH = n / 3.0 x 10^-1 L n= 6.0 x 10^-1 moles NaOH After finding the molar mass of NaOH (39.998 g/m...