CHEMISTRY COMMUNITY

DianaTrujillo2K

Can someone please explain how I would go about solving this problem? It reads: Lex Luthor finds a sealed box that has two compartments. He puts 9.00g of Helium gas in the first compartment, and 125g of Krypton gas in the second. The compartment with Krypton is 3 times the size of the compartment wi...

DianaTrujillo2K

You are correct. It takes a lot of energy to break the hydrogen bonds in water. Also water is slightly polar so energy is also needed to break the bonds between H2O molecules.

DianaTrujillo2K

When you use the equation given on the equations sheet for tests, you always subtract E°cathode-E°anode leaving the numbers as they are given to you. Another way to solve for E°cell is to determine which is the cathode and which is the anode. Once you have determined which is the anode you change th...

DianaTrujillo2K

The order of a rate law is determined experimentally using the method of initial rates or by looking at the graphs. When the observed rate law is given along with the elementary steps of a reaction, you can use the pre-equilibrium approach to determine the slow step that determines the rate of the o...

DianaTrujillo2K

The equation to use here is q=mCΔT. The heat lost by the tea will be transferred to the ice , therefore q(ice)= -q(tea). However, the ice will melt as it heats up so the ΔH(fusion) of water must be added to the side with the q(ice). Plug in the values and leaving T(final) as x for both sides. Solve ...

DianaTrujillo2K

For a galvanic cell the over charge of the cell must be positive, so you determine which one to switch based on which one will make the charge positive.

DianaTrujillo2K

The problem will likely not tell you. You determine the slow step by finding the rates of every step starting in step 1. If the rate for step 1 does not match the overall rate law then it is not the slow step and you will have to check step 2. You go in order finding the rate laws of each elementary...

DianaTrujillo2K

The order of a rate law is determined experimentally and cannot be determined using the coefficients in the reaction. However, when using the pre-equilibrium approach you use the coefficient as the exponent, but this can only be done when the observed rate law is given and you are trying to determin...

DianaTrujillo2K

The equation for entropy is q rev/ T. The heat lost by the system will be gained by the surroundings and vice versa. So on the equations for entropy will have -q. Furthermore, when the system loses entropy, the surroundings gain it. Hope this helps!

DianaTrujillo2K

This is because any heat lost by the system is gained by the surroundings and vise versa; therefore, q has opposite signs.

DianaTrujillo2K

I believe catalysts are in the first step as a reactants and get cancelled out later in the mechanism. An intermediate is produced within the mechanism and then cancelled out. Both are cancelled, but a catalyst is a reactant in the beginning of the whole mechanism while an intermediate is made withi...

DianaTrujillo2K

Chlorine is an intermediate because it is produced in step 1, but it is used as a reactant in step 2; therefore, they cancel out, and the overall reaction does not include it.

DianaTrujillo2K

Coefficients do not matter when determining oxidation states. They only matter when determining how many electrons were transferred.

DianaTrujillo2K

I do not fully understand your question, but the reducing agent gives electrons while the oxidizing agent receives electrons. Sometimes an element or compound can act as both.

DianaTrujillo2K

One way we have learned to determine the order of each reactant in a reaction is the method of initial rates. Using this method we run many experiments and determine the order of each reactant by seeing how a change in initial concentration of a reactant changes the initial rate of the reaction. Add...

DianaTrujillo2K

The rate law is determined experimentally; the stoichiometric coefficients are not enough to write a rate law and determine the order.

DianaTrujillo2K

Can someone explain what the half life of a reaction is? And why would we be interested in a half life of a reaction?

DianaTrujillo2K

I believe their order is determined based on their standard reduction potentials. The ones with the smallest reduction potentials are the ones with the most reducing power.

DianaTrujillo2K

To determine the order of the overall reaction you add the orders of the reactants.

DianaTrujillo2K

Yes, water is always necessary to balane the oxygen in both basic and acidic solutions. In basic solutions, water is also needed to balance out the hydrogen.

DianaTrujillo2K

To solve this problem you find the heat needed to raise the temperature of the pot to 100 degrees C and the heat required to raise the temperature of the water to 100 degrees C. You add the heat values to answer the first question. To find the percentage of heat used on the water, you divide the hea...

DianaTrujillo2K

A rate constant represents how fast a chemical reaction will take place based on the concentrations of the reactants and products. You find it by plugging in the molar concentrations into your rate equation with their respective order and equaling it to the rate of the reaction.

DianaTrujillo2K

Pt(s) is included in the outer portion of cell notation when it is being used as an electrode. Pt(s) is used as an electrode when there is no solid in the half reaction. It is needed to transport or receive electrons, but it does not react.

DianaTrujillo2K

It does not necessarily have to be like that, but people and textbooks usually put the anode on the left. However, on an exam it could be the other way around. Essentially it does not matter. You just have to make sure which is which by checking the half reactions.

DianaTrujillo2K

The anode half cell is where oxidation happens. The cathode part is where reduction happens. During oxidation there is a loss of electrins. Dheing reduction there is a gain of electrons.

DianaTrujillo2K

Can someone explain why delta U is 0 in the isothermal expansion of an ideal gas?

DianaTrujillo2K

Hello Diego!

Yes there will be lecture that day.

DianaTrujillo2K

We use an equation to calculate delta G based on the information we are given in the problem.

DianaTrujillo2K

Can someone elaborate on what the max potential of a cell means?

DianaTrujillo2K

What is the difference between ∆G and ∆G°?

DianaTrujillo2K

In expansion work the pressure is usually constant and given in the problem; therefore the equation is work=−PΔV.

DianaTrujillo2K

Under what conditions if any is the change in internal energy and the change in enthalpy the same?

DianaTrujillo2K

Heat is a path function because the amount of heat a system has is based on how it went from one state to another; however, enthalpy only depedns on the final and initial states.

DianaTrujillo2K

Test 1 will not have calculations on work and internal energy. Only conceptual questions will appear on these topics. We do not have to read 8.18 and 8.20.

DianaTrujillo2K

If it is said that system requires heat then the sign of q will be positive because the system is absorbing heat. You can tell the sign of q based on the wording. If a system cools down or gives off heat then the sign of q will be negative.

DianaTrujillo2K

Will there be any approximation chemical equilibrium problems on the final?

DianaTrujillo2K

Localized electrons stay in between two atoms. Delocalized electrons are not confined to any space and go outside their boundaries.

DianaTrujillo2K

Can someone explain chelating complexes to me, and why is 17.35 have B as the one to form a chelating complex?

DianaTrujillo2K

The double bond counts as one domain of electron density and when determining hybridization the type of bond does not matter. Only the number of electon domains, so it would be sp^2.

DianaTrujillo2K

Each pair of electrons occupies one sp^3 orbital. There is no different rule for hybridization of central atoms with lone pairs; therefore, the oxygen in water has 4 sp^3 orbitals.

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