CHEMISTRY COMMUNITY

Christy Zhao 1H

Because the anode metal is a solid, the Ecell won't be affected. Ecell is dependent on concentration and temperature.

Christy Zhao 1H

If you flip the sign, use Ecell=Eanode+Ecathode. If you don't flip the sign, use Ecell= Ecathode-Eanode.

Christy Zhao 1H

Both equations are also given on the constants sheet. And the C value can be Cv at constant volume, or Cp at constant pressure.

Christy Zhao 1H

If a half reaction is multiplied by 2 to get an equal number of moles of electrons in both half reactions to be able to cancel each other out, then yes n=2.

Christy Zhao 1H

How do you know to use the equation $\Delta U=(3/2)nR\Delta T$ ?

Christy Zhao 1H

Adding on to the comment above, you can also use the equation $E=\frac{RT}{nF}lnK$ to solve for K.

Christy Zhao 1H

Why can't chemists prank their friends?
They lack the element of surprise.

Christy Zhao 1H

The integrated rate laws of the zero and first-order have a -kt, while the second-order has a +kt. Since the integrated rate laws correspond to y=mx+c (m=k), the slope depends on k.

Christy Zhao 1H

Adding on to the comment above, -k would be for zero and first-order reactions, and k would correspond to second-order reactions.

Christy Zhao 1H

How do you know when to use Pt or graphite?

Christy Zhao 1H

The opposite goes for oxidizing agents; the more positive the standard cell potential, the stronger the oxidizing agent.

Christy Zhao 1H

Are there any other special cases like liquid Hg where it can be considered as an electrode?

Christy Zhao 1H

A salt bridge allows the flow of ions to complete the electrical circuit without affecting the cell potential.

Christy Zhao 1H

Electrolysis occurs in electrochemical cells and drives reactions in their nonspontaneous directions through an electric current.Electrolysis can be used to to predict how much products form from an electric current flow.

Christy Zhao 1H

If you were confused with the subscript, page 571 says, "The subscript r is always the signal that we are using this 'molar' form."

Christy Zhao 1H

Here is the link to the errors in the solution manual for future reference!
https://lavelle.chem.ucla.edu/wp-conten ... rs_6Ed.pdf

Christy Zhao 1H

On page 348 of the textbook, there is a helpful diagram that shows that a negative change in Gibbs free energy is spontaneous.

Christy Zhao 1H

Since the flask is getting colder, it is an endothermic reaction because the flask(as the surroundings) is losing heat. Therefore, the heat from the flask is going into the reaction.

Christy Zhao 1H

Adding to the comment above, the system is spontaneous when delta G is negative because G is energy, and decreases in energy are spontaneous.

Christy Zhao 1H

The compound becomes more unstable when the change in entropy is negative and temperature increases. So, after the standard entropies of formation are calculated, PCl5 would be the compound that is less stable since it is negative.

Christy Zhao 1H

Yes, you would calculate the change in entropy for the change in volume and the change in pressure, and add the entropy changes together.

Christy Zhao 1H

Adding on to the post above, pg. 268 of the textbook says that in an adiabatic system, the change in internal energy is equal to the work done.

Christy Zhao 1H

Keep in mind that for reversible expansion processes, the work done is the maximum work possible, therefore more work is done compared to irreversible expansion processes.

Christy Zhao 1H

What do hungry chemists eat?
Gram (Graham) crackers

Christy Zhao 1H

When work is done to the system, energy is added and work is positive. When work is done by the system, energy leaves the system and work is negative.

Christy Zhao 1H

Another example is an uncovered pot of hot water. Matter is leaving the system through the steam, and energy as heat is also lost.

Christy Zhao 1H

Also, keep in mind that a reversible process does more work than an irreversible process.

Christy Zhao 1H

On the other hand, if work was done by the system, the internal energy of the system would have decreased.

Christy Zhao 1H

An example would be a hot cup of water. Heat from the hot water is released into its surroundings, and matter can be exchanged by drinking some of the water, or through the steam that is released into the air.

Christy Zhao 1H

In section 8.1 of the book, it gives an example of a closed system: a cold pack. Energy can be exchanged, but not matter.

Christy Zhao 1H

Adding on, you should get 0.05 M H2O for the initial concentration, and you know x=0.040 from H2. The equilibrium concentration for H2O is 0.05-x, and plugging in x you would get 0.01 M H2O.

Christy Zhao 1H

Yes, ligands are written in alphabetical order when writing the formula. Toolbox 17.1 goes into detail about writing chemical formulas.

Christy Zhao 1H

An amphiprotic example would be water since there are hydrogen atoms and is able to donate a proton, and the oxygen has lone pairs and is able to accept a proton.

Christy Zhao 1H

Substances that are amphoteric can act as an acid or base, so they can donate protons or accept protons.

Christy Zhao 1H

"Because single bonds and multiple bonds are treated as equivalent in the VSEPR model, it does not matter which of the Lewis structures contributing to a resonance structure we consider" (pg. 112).

Christy Zhao 1H

Bonding pairs are held in place by two atoms unlike lone pairs, so lone pairs are able to take up a larger space.

Christy Zhao 1H

Adding on, it would be linear because single and multiple bonds are treated as the same in the VSEPR model.

Christy Zhao 1H

Since lone pairs have a greater electron repulsion than electrons in bonds, these lone pairs push the bonded atoms closer together.

Christy Zhao 1H

The larger the bonding atoms are, the distance between them is also larger, and the bond becomes weaker.

Christy Zhao 1H

This equation works for particles with momentum, and it has wave-like properties with wavelength.

Christy Zhao 1H

Keep in mind that the formal charge of the model should add up to the overall charge of the atom.

Christy Zhao 1H

The electronic configuration is written based on the principle quantum number(n), in the order of increasing energy. S blocks have a greater n value than d blocks.

Christy Zhao 1H

It can be determined by calculating the formal charge of the element. The lower the number of formal charges, the more stable the structure.

Christy Zhao 1H

A wave function and orbital have the same meaning. In the textbook it says, "wavefunctions of electrons in atoms are called atomic orbitals."

Christy Zhao 1H

Just to reiterate, keep in mind that the node is where the wavefunction passes through zero, it doesn't just reach zero.

Christy Zhao 1H

You also use Planck's constant in the equation relating the kinetic energy of an ejected e- to the energy of an incident photon.

Christy Zhao 1H

Adding on, one photon interacts with one electron, and each photon must have enough energy to eject one electron to be absorbed. So if 1 million photons are absorbed, 1 million electrons are excited to a higher energy level.

Christy Zhao 1H

I'm still a bit confused about the Balmer and Lyman series. Are we just supposed to know that Balmer series are in the visible region and Lyman series are in the UV region?

Christy Zhao 1H

I understand that we have to multiply the mole ratios to get as close to whole numbers as possible, but to what extent would the decimal be considered too far from a whole number? For example if I get 1.86, would I still be able to round that to 2?

Christy Zhao 1H

I'm confused with part d. How would I go about to find what fraction of the total mass of the sample was due to oxygen?

Search found 50 matches