CHEMISTRY COMMUNITY

MSkye Goldwater 2K

I was wondering if anyone knows if the values for bond dissociation energy will be provided or if we have to solve for it. The values are listed as part of the answer for 11.99 a) in the solutions manual. If we aren't provided those values, what is the method for solving for it?

MSkye Goldwater 2K

I'm having the same problem. For example with homework problem 9.19 the equation delta-S = nCln(T2/T1) is used. However, in this case they just ignored the n so the resulting answer ended up in J/(k x mol). I thought that when they don't give the number of moles and you are using this equation, you ...

MSkye Goldwater 2K

In order to solve homework question 9.25, you need to first determine the number of possible molecular orientations. I'm wondering if the only way to figure it out is to draw them all. Is there a math based way or any faster way to determine it?

MSkye Goldwater 2K

I noticed in the solutions manual that sometimes a + sign is used for a positive change in something and sometimes it isn't. How do I know when to use it and when not to?

MSkye Goldwater 2K

The energy gained by the ice is equal to the energy lost by the water. However, if the water has enough energy to heat the ice to 0 degrees C and melt it, then to get the melted ice to the final temperature you will need to use the specific heat of liquid water even though it would be on the same si...

MSkye Goldwater 2K

It's also important to know which direction the phase changes are occurring because you may have to multiply the delta-H by -1 if you are freezing instead of melting for fusion or if you are condensing instead of vaporizing for vaporization.

MSkye Goldwater 2K

When drawing the phase change diagram for a given substance, how do we determine the steepness of the gas, liquid, and solid phases? Also, how do you know which line you draw longer, the heat of vaporization or the heat of fusion?

MSkye Goldwater 2K

Thermal equilibrium only occurs when the temperatures of the objects are the same. It does not matter how long it would take for the temperatures to even out, but equilibrium will not be established until then.

MSkye Goldwater 2K

In those certain problems that we are dealing with, they have to either give us the final temperature of the system, or the total heat transferred between the ice and the water. With either of these pieces of information, you should be able to determine if the ice will completely melt.

MSkye Goldwater 2K

They are two ways to find the standard gibbs free energy of a reaction. However, depending on the information you are given to start with and what you are trying to solve for, you may want to use one over the other.

MSkye Goldwater 2K

All the above is correct. It being an isolated system is extremely important and is why bomb calorimeters are extremely useful. This allows for the very accurate calculation of the energy released when a substance has been combusted.

MSkye Goldwater 2K

Would you have to take into account the number of moles of gas in relation to the balanced equation when solving for q ?

MSkye Goldwater 2K

You can only use this equation when you are dealing with an ideal gas. The deltas imply that a change is occurring. You can use this in these 2 formulas:

delta H = delta U + nR (delta T)
delta H = delta U + (delta n) RT

MSkye Goldwater 2K

The difference between velocity and speed is something we don't really need to think about in this course. While both q and w have units of energy (typically J or kJ) when used in the 1st law of thermo equation, q and w are quite different. q is heat which has to do with the thermal energy and w is ...

MSkye Goldwater 2K

q is the general symbol we use for heat and it is a path dependent function. H is the general symbol for enthalpy and it has the definition of H = U + PV which is derived from the 1st law of thermodynamics. H is a state function while q is a path dependent function. This is why in many of the proble...

MSkye Goldwater 2K

An isolated system has no contact with its surroundings. The way the book puts it is that an isolated system can exchange nothing (neither work nor matter) with its surroundings.

MSkye Goldwater 2K

Question number 8.25 states that there is a temperature rise of 7.32 C. Why is it that because the degree Celsius is the same size as the degree kelvin, “per C” is the same as “per K" ? Isn't it normally that to convert Celsius to Kelvin you have to add 273.15 ?

MSkye Goldwater 2K

Question 8.21 states, "A piece of copper of mass 20.0 g at 100.0 degrees C is placed in a vessel of negligible heat capacity but containing 50.7 g of water at 22.0 degrees C. Calculate the final temperature of the water. Assume that no energy is lost to the surroundings." The solutions m...

MSkye Goldwater 2K

The book describes how they derived it in the "How Do We Do That?" box on page 280

CHEMISTRY COMMUNITY

Search found 19 matches

11.99 Bond dissociation energy

Re: Units Confusion [ENDORSED]

Homework problem 9.25: orientations of a molecule

When to use + sign

Re: heat capacities

Re: Calculating the Change in Enthalpy

Phase Change Diagrams: Slopes

Re: Heat Capacity

Re: Question regarding ice in water?

Re: Gibbs free energy equations

Re: Bomb calorimeter

Re: constant pressure

Re: PdeltaV=deltanRT

Re: Work vs. Heat

Re: State function in relation to heat

Re: Isolated system

Celsius the same as Kelvin? [ENDORSED]

First Law and Calculating Final Temp (question 8.21)

Re: Cp,m --> Cv,m