CHEMISTRY COMMUNITY

BAlvarado_1L

pH=-log[H+] and strong acids cause there to be a high [H+] than weak acids this strong acids have a pH closer to 0 while weak acids are closer to 7 on the scale of 0-7

BAlvarado_1L

kelvin so it cancels out with the units of R

BAlvarado_1L

zero-order rate isn't dependent on the reactant concentrations and has a linear graph when [A] is graphed vs time

BAlvarado_1L

the left of the double line is being oxidized while the right is being reduced (you can remember this because of the two r's)

BAlvarado_1L

a large k means a faster reaction rate

BAlvarado_1L

the slow step takes the most time and the reaction cannot be completed before this step is completed, it determines the reaction rate therefore

BAlvarado_1L

that indicates that PV=nRT is applicable

BAlvarado_1L

to get a linear graph for each type of order do the following:
0th- [A] vs time
1st- ln[A] vs time
2nd- 1/[A] vs time

BAlvarado_1L

BAlvarado_1L

BAlvarado_1L

y-axis: 1/[A]
x-axis: time

BAlvarado_1L

Dear Dr. Lavelle, Thank you so much for your positive energy this year. Your lecture is very clear and productive however, it is your evident love for teaching that makes it so amazing. Thank you for all of your resources and the quick and smooth transition to an online final, I cannot imagine how s...

BAlvarado_1L

changing the size of the anode doesn't affect the voltage

BAlvarado_1L

you can change the concentration to affect the voltage

BAlvarado_1L

How do we know the value of 'n' for concentration cells

BAlvarado_1L

thanks

BAlvarado_1L

the anode is being oxidized so you must flip the equation since all cell potentials are given in the reduction form

BAlvarado_1L

Your answer will be given in KJ

BAlvarado_1L

concentration cells always have a smaller delta E than galvanic cells because the difference in the standard potential=0

BAlvarado_1L

the difference in the standard potentials is zero because they have the same standard potential, they're the same solution

BAlvarado_1L

to find n you must either balance the half equations to get the number or you can look at the standard enthalpy table to find number of electrons needed in both equations and set those equal to each other

BAlvarado_1L

delta G is given in kJ

BAlvarado_1L

you shouldn't write the stoichiometric coefficients

BAlvarado_1L

For part b what is the standard potential for In 3+ -> In2+? This value would be different than the transition from In3+ to In (s) right?

BAlvarado_1L

galvanic cells are positive while electrolysis is negative a helpful way to remember this is by knowing that electrolysis requires electricity to occur

BAlvarado_1L

what is the half-reaction in part d for Cl2 -> Cl2?

BAlvarado_1L

the coefficients don't affect the standard potential but make sure to change the sign if you need to flip the equation given in the table

BAlvarado_1L

the last lecture it will cover is the start of class this Wednesday, it won't include kinetics

BAlvarado_1L

make sure to write the state of the compound but you don't need to include the coefficient which means you don't need to find the balanced equation unless asked for separately

BAlvarado_1L

the cell diagram should always have the cathode on the right so your method should be correct but to avoid getting the wrong answer due to an error in the set up of the cell diagram remember that it is E cathode - E anode

BAlvarado_1L

For an ideal gas, in an isothermal process, ΔU=0=Q−W, so Q=W. delta H is zero for isothermal reactions with ideal gases.

BAlvarado_1L

you can guess that the entropy would be decreasing based on the state change of SO2 and BR2 from gas to aq, we know gas has a much larger entropy.

BAlvarado_1L

what formula is used to find the enthalpy of fusion in question 3b

BAlvarado_1L

the easiest way to solve problems like these is to find chemicals that you want in your final equation that only appear once in the other equations. In 4a ginger ale only appears in the first equation so you know you must multiple that equation x2 to get the 2gingerale you see in the final equation....

BAlvarado_1L

you can use Hc the same way you would use Hf mathematically but Hc stands for enthalpy of combustion

BAlvarado_1L

I don't think that we've had a practice problem in which we weren't told if a reaction was reversible vs irreversible if that information was needed but an example of a irreversible reaction would be combustion. If a reaction is spontaneous the gibbs free energy value would be negative

BAlvarado_1L

if you burn fuel what does it mean conceptually for the Delta U to be negative? can the system then not do work?

BAlvarado_1L

if you can use equation -P deltaV to find work done from expansion how do you convert this to joules? my answer is in ATM x L

BAlvarado_1L

It can but it is not a given that all thermodynamically unstable compounds will decompose. There are three types of decomposition reactions: Thermal, electrolytic, and catalytic.

BAlvarado_1L

these compounds are not in their standard state, for example- C(s, graphite) + O2(g) → CO2(g)
C(s) and O2(g) are their standard states with standard enthalpies of formation=0

BAlvarado_1L

This equation is used to find delta S of melting ice, delta H is the heat required to melt 1 mol of ice at 1atm divided by the melting point in Kelvin

BAlvarado_1L

This can be shown from:
deltaH = (qp + w) + PdeltaV -> deltaH = (qp - PdeltaV) + PdeltaV -> deltaH= qp

BAlvarado_1L

Assuming that the only work done by the reaction is work of expansion gives an equation in which the P deltaV terms cancel.

BAlvarado_1L

q is negative if the reaction is exothermic a bomb this will be indicated by an increase in the thermometer of the bomb calorimeter

BAlvarado_1L

The cylinder for the problem is in an environment that has 750 Torr. The conversion for Torr to atm is 760Torr/1atm so the environment we are working with would have a pressure slightly less than 1atm

BAlvarado_1L

Reversible processes do the most work, because they have to push against more external pressure

BAlvarado_1L

the standard enthalpy is 0 because it takes no energy to form a naturally-occurring compound

BAlvarado_1L

How are we supposed to find the concentrations of Ba2+, OH−, and H3O+ if we aren't given the Ka or pH?

BAlvarado_1L

This happens for more than just water, you can google the phase change of other compounds to find examples.

Search found 49 matches