CHEMISTRY COMMUNITY

Sophie 1I

I'm a little confused on how you get this answer...

C6H12O6 (s) + 6 O2(g) → 6 CO2(g) + 6 H2O(l) ∆H°rxn=-2805 kJ.mol-1
Explain why ∆S°rxn for the above reaction should be positive or negative

the answer is that: 1 mol of solid → 6 mols of liquid ∆S°rxn for the above reaction is positive

Sophie 1I

K=k/k' so if k is bigger the equilibrium constant will increase.

Sophie 1I

I believe that it's not included in the overall reaction because it cancels with the Cl from step 1

Sophie 1I

For the reaction 2O3(g)->3O2(g) why would the rate law be k[O3]^2/[O2]?

Sophie 1I

It can help you to identify the rate constant.

Sophie 1I

The most important thing is to make sure that all of your units are consistent, and to see if the problem asks you for specific units.

Sophie 1I

It would be helpful to know and understand it but you shouldn't be expected to derive it on a test

Sophie 1I

Yeah it looks like they just converted everything to mol, I also got 2.85 for c because I didnt convert to mol

Sophie 1I

So then it wouldn't matter whether you had the actual initial concentration?

Sophie 1I

Reactant concentration is decreasing so the slope will be negative so therefore k must be negative.
Second order reactions of 1/[A] has a positive slope so k is positive

Sophie 1I

T will usually be a given temperature and R is a constant on the formula sheet.
R= 8.314JK^-1mol^-1

Sophie 1I

An easy way of rememberin gthis is to to take (M^1-x)/s where s is the order of the reaction.
For example, for a 1st order reaction 1-1=0 and M^0=1 so the unit for k will be 1/s for 1st order rxn.

Sophie 1I

I'm having trouble understanding when and why we need to reverse the anode reactions... any help would be appreciated!

Sophie 1I

That makes a lot of sense thank you!!

Sophie 1I

For 14.11 d the question is about writing the half-reactions and balanced equations for the cell reaction of galvanic cells. On part D, why is does the half reaction of the anode have H+ on the left side instead of the right?

Sophie 1I

q is zero when there is no heat lost or gained. In the isothermal system q is equal to -w

Sophie 1I

The charges on either side should equal each other and if their not they it needs to be balanced

Sophie 1I

I know that delta U is 0 for isothermal reactions but I'm not sure why that is

Sophie 1I

In a sample of 1 mol of gas initially at 1atm and 298K thats heated at constant pressure to 350K, and is then compressed isothermally it its initial volume and finally cooled to 298K at constant volume, why is Delta G 0?

Sophie 1I

From lnK=ΔG°/-RT you take e^x of both sides so the ln will cancel and you will have e^whatever ΔG°/-RT is

Sophie 1I

The "ideal" cooler does not exchange heat or matter with the surroundings and system.

Sophie 1I

Heat can be generated inside the system which causes the change in temperature

Sophie 1I

Not necessarily for this equation.

Sophie 1I

It's given that C at constant Pressure equals=5/2R the C at constant volume is given to be 3/2R
R is a given constant that equals R = 8.314 J·K-1·mol-1

Sophie 1I

A change in pressure(delta P) does not necessarily mean that pressure is 0 it just means that the pressure is constant. The equation for work uses the actual pressure not the change in the pressure.

Sophie 1I

In question 8.19 part b it asks what percentage of the heat calculated in part a, which was 1.4x10^2 kj, is used to raise the temperature of the water? the answer is ((1.3x10^5J)/(1.45x10^5J))x100=90% but I'm not sure where these numbers come from

Sophie 1I

Change in internal energy is the sum of the energy terms so it is equal to q + w so you just add 524kJ and 340kJ

Sophie 1I

When there is a phase change, such as when going from a solid to a liquid (melting), heat is required although the temperature does not change. Melting is an endothermic reaction so q will be positive and work is done by the system because it's losing energy so w is negative. Condensation work is po...

Sophie 1I

Delta H is the change in enthalpy which is equal to change in U +P*change in V and the delta U is the change in internal energy of the system.
q is the heat of the system.

Sophie 1I

Enthalpy is determined by the current state of the system and and is therefore independent of how the state was prepared. It is not reliant on the path of the system.

Sophie 1I

Sublimation is a type of phase transition of a substance from solid to vapor without going through the liquid phase.

Sophie 1I

The De broglie equation is wavelength=h/p where p=mv with the v relating to velocity of a particle not the frequency. If you were given the frequency and asked to find the wavelength you would use c=wavelength times frequency. So basically you use De broglie when comparing wavelength to its mass and...

Sophie 1I

Work functions are used when you are trying to find the kinetic energy of an ejected electron in which case you would take the energy supplied by the photon minus the work function.

Sophie 1I

To find the velocity of the ejected electron you use the kineticE=(1/2)mv^2 equation. You then plug in energy of the ejected electron given to you in part a and set it equal to 1/2 times the mass of an electron times v^2. You do not need to use the work function.

Sophie 1I

They must be in alphabetical order without the prefixes.

Sophie 1I

When comparing bases, what do you look at to determine which base is stronger?

Sophie 1I

Sigma bonds refer to one single bond. In a double bond you can think of the first bond as being a sigma bond and the rest of the bonds being pi bonds. So a double bond will have one sigma bond and one pi bond and a triple bond will have one sigma bond and two pi bonds.

Sophie 1I

Okay thank you!

Sophie 1I

How can you tell the difference between a strong and a weak acid and strong and weak base by looking at the reaction equation?

Sophie 1I

Pi bonds can only overlap side by side with electron densities on each side of the internuclear axis so if it rotated the bond would be broken.

Sophie 1I

Sigma bonds are always the first bonds to form and are single bonds and the remaining bonds are pi bonds. In an example of N2, the 2 pi bonds will appear to surround the single sigma bond when the electron densities of the pi bonds combine.

Sophie 1I

A non-polar bond has equal sharing of the bonding electron pair and usually takes place between nonmetals so the dipoles cancel and ha a dipole moment of zero. A polar bond has unequal sharing of the electron pair so there is a nonzero dipole moment. Ionic bonds have a difference in electronegativit...

Sophie 1I

Hybridization is the merging of two different orbitals to form a new atomic orbital which can change the bonding properties.

Sophie 1I

On a homework problem for writing the lewis structure for ClCN, why would Carbon form a triple bond with nitrogen and a single bond with chlorine instead of a double bond with both Nitrogen and chlorine?

Sophie 1I

Either way is probably fine, just check to make sure it doesn't specify for a specific one in the problem.

Sophie 1I

My TA told us that the test will cover 1.6 through CH 2

Sophie 1I

Yes, a node is where the wave function passes through zero

Sophie 1I

Yes, if a photon has energy of the photon is greater than or equal to the work function the electron will be removed

Sophie 1I

I would use 2.9988x10^8 just because it is more accurate; however, if 3.00x10^8 was the number given in the problem then I would use that one instead.

Sophie 1I

Yes, because there was a reaction with oxygen leading to the production of carbon dioxide and water!

Sophie 1I

Some temperature conversions that are good to know:
When going from Celsius to Kelvin you add 273.15 to the temperature in Celsius (and subtract 273.15 going from kelvin to celsius)
Celsius= (Fahrenheit-32)x(5/9)

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