CHEMISTRY COMMUNITY

Niyanta Joshi 1F

what kind of fish has only 2 sodium atoms?
2 Na

Niyanta Joshi 1F

I don't like atoms, I heard they make up everything...

Niyanta Joshi 1F

If a king farts, is it a noble gas?

Niyanta Joshi 1F

Can rate law constant ever be negative?

Niyanta Joshi 1F

Can we use the half life formulas for zero order and second order in practical life examples?

Niyanta Joshi 1F

The integrated formula derived for the first order is [At] = [A0]*e^-kt. This gives an exponential graph of [At] against time and a decreasing graph with the slope of -k when graphed for ln[At] against time.

Niyanta Joshi 1F

Let's say, if the first step of the reaction is the slowest step, the overall reaction cannot proceed any faster than this first elementary step. So the slowest step is always the rate- limiting step and therefore it determines the overall rate of the reaction.

Niyanta Joshi 1F

Why does the first order half life not depend on the initial concentration of reactant? Also, would higher temperature of the reaction lead to a slower half life?

Niyanta Joshi 1F

Kinetic stability deals with the rate of reaction. The slower the reaction, the more kinetically stable the reaction is. Thermodynamic stability deals with the spontaneity of the reaction, which depends on the Gibbs free energy. Graphite is more thermodynamically stable than diamond. But the reactio...

Niyanta Joshi 1F

Kinetic stability deals with the rate of the reaction. The slower the reaction, greater the kinetic stability. Whereas thermodynamic stability will depend on whether the reaction is spontaneous or not.

Niyanta Joshi 1F

I think I read in the one of the examples in textbook (15.1) that its just better practice to choose multiple of units that minimize the power of 10 shown explicitly.

Niyanta Joshi 1F

Unique rate is positive for the product being formed and negative for the reactant/s being used up. This rate should be the same for the reactants and products in a chemical reaction. Its basically the rate of appearance/disappearance of reactant/products divided by their stoichiometric coefficients.

Niyanta Joshi 1F

Q is usually used to determine which direction the reaction will have to shift towards to reach chemical equilibrium.

Niyanta Joshi 1F

Yes, we can only use W=-P delta V, for a constant external pressure i.e irreversible reaction.

Niyanta Joshi 1F

When the cell is spontaneous, the one with the highest reduction potential should be the reduction half-reaction and so it should act as the cathode. The one with the lower reduction potential as the oxidation-half reaction and so it should act as the anode.

Niyanta Joshi 1F

delta S (universe)= delta S (sys) + delta S (surr)
When the reaction is at equilibrium and it is a reversible reaction, the total delta S of the universe is zero.
Hence, delta S (sys) = - delta S (surr) for these conditions.

Niyanta Joshi 1F

When it is reversible work, we use the equation W=-nRTln(v2/v1)
When it is irreversible work, W= -Pext (v2-v1)

Niyanta Joshi 1F

For a system,
Isothermic = constant temperature
Isochoric= constant volume
Isobaric= constant pressure
Isometric= constant dimensions or measure

Niyanta Joshi 1F

During a process, energy cannot be completely transferred. Some of the transformational energy will be dissipated in the surrounding environment as heat during the process This energy cannot be recovered, therefore it is not a reversible process.

Niyanta Joshi 1F

There is no net change in internal energy as all the heat is used to to do expansion work against the surroundings.

Niyanta Joshi 1F

Van't Hoff equation accounts for the Le Chateliers Principle we learned earlier, it is useful to understand effect of temperature on equilibrium.

Niyanta Joshi 1F

An example of adiabatic system could be when change in temperature = 0, no heat flow(q=0), but work is being done, like in an insulated container with the gas filled in it expanding.

Niyanta Joshi 1F

Also, absolute zero is a theoretical concept. It may not be achieved experimentally. This is because from the second law of thermodynamics, we know that heat will spontaneously move from a warmer body to a cooler body, so the object that one tries to cool to absolute zero will try to take in heat fr...

Niyanta Joshi 1F

I believe we are expected to understand how the equations come into place, however I doubt that we would actually need to do calculations to derive the equation on the test.

Niyanta Joshi 1F

Heat Capacity is the ratio of heat supplied/absorbed to the corresponding rise in the temperature; in other words it is the amount of heat required to raise the temperature of a substance by 1 degree C. But this does not tell us how much mass of the substance we are measuring. Heat capacity is an ex...

Niyanta Joshi 1F

I found it interesting that although work and heat are interchangeable forms of energy, while work can be fully transferred into heat, the vice versa is not true. This is because if heat is fully transformed into work, it would violate the laws of entropy, i.e, a closed system's entropy cannot decre...

Niyanta Joshi 1F

Also, it seems very hard to find a truly isolated system, except for the universe as a whole, because we have to account for the gravity on any system with mass.

Niyanta Joshi 1F

Yes, ΔH= (energy needed to break the reactant bonds) - (energy released by forming the product bonds) gives the change in enthalpy for the reaction

Niyanta Joshi 1F

Work is a state property as it is directly proportional to the object's distance moved against the opposing force and this distance depends on the path taken. Since deltaU = W + q, and work is a state function, it seems that the heat given off must be dependent on the path as well.

Niyanta Joshi 1F

When the air is compressed, work is done ON the system(i.e. air) by the surrounding, which increases the internal energy of the system and hence the work wrt air is positive. If I'm understanding the hypothetical correctly, if the air expands, work is done BY the system(air) on the surrounding(pump ...

CHEMISTRY COMMUNITY

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Re: Post All Chemistry Jokes Here

Re: Post All Chemistry Jokes Here

Re: Post All Chemistry Jokes Here

Rate law constant

Half life

Re: Slope of 1st order RXNs

Re: reaction mechanism

First Order- Half life

Re: Kinetically Stable Vs. Thermodynamically Stable

Re: Kinetics vs Thermodynamics

Re: Homework 15.19

Re: unique average rates

Re: Q

Re: Work when pressure is constant

Re: Anodes vs. Cathodes

Re: delta S(system) vs delta S(surroundings)

Re: Reversible vs Irreversible

Re: Isothermic

Re: Question about "Real Processes"

Re: Delta U (Concept Clarification)

Re: Van't Hoff Eq.

Re: Adiabatic system

Re: Third Law of Thermodynamics

Re: The integral equation

Re: Heat Capacity vs Specific Heat Capacity

Re: Heat versus work

Re: isolated sytems

Re: Bond Enthalpies

Re: State Properties: q vs. qp

Re: The First Law: Problem 8.3