CHEMISTRY COMMUNITY

Jesse Anderson-Ramirez 3I

Work done on the system is positive. Work done by a system is negative.

Jesse Anderson-Ramirez 3I

Should use Kelvin so the units match the constant.

Jesse Anderson-Ramirez 3I

Delta U is the change in internal energy while delta H is the change in enthalpy.

Jesse Anderson-Ramirez 3I

For a system to be considered reversible, delta S must equal 0.

Jesse Anderson-Ramirez 3I

Extensive properties depend on mass and intensive properties do not.

Jesse Anderson-Ramirez 3I

flat areas of the graph are where phase changes are occurring. At these instances temperature is constant because all energy is being used to change phases.

Jesse Anderson-Ramirez 3I

If the question asks for the change in temperature you can use either. If not, you need to look at what units are used in the question or which units are used in the constants.

Jesse Anderson-Ramirez 3I

It depends on the circumstance but in general, the reaction will shift in the direction that allows for it to reach equilibrium. For example, if Q (reaction quotient)<K(equilibrium constant) the reaction will shift to the right because the concentration of reactants is greater than the concentration...

Jesse Anderson-Ramirez 3I

I know that K represents the equilibrium constant, but what does Q represent in this situation? In this situation, Q would represent the state of the reaction at a point where equilibrium has not been reached yet. This is why they are asking about which direction the reaction will occur ("left...

Jesse Anderson-Ramirez 3I

You need to use the constant that has the same units as the values given in the question as you need units to cancel out.

Jesse Anderson-Ramirez 3I

Only when change in pressure and change in volume are zero.

Jesse Anderson-Ramirez 3I

While a phase change is occurring the temperature is constant, but once the phase change is complete the temperature will continue to change.

Jesse Anderson-Ramirez 3I

Does the type of calorimeter affect the problem at all? Or do the equations work the same regardless of the type of calorimeter?

Jesse Anderson-Ramirez 3I

Energy can be transferred in a closed system while in an isolated system energy can't be transferred.

Jesse Anderson-Ramirez 3I

A bomb calorimeter is able to withstand more pressure and is more precise.

Jesse Anderson-Ramirez 3I

The constants will be given on the formula sheet during the exams.

Jesse Anderson-Ramirez 3I

If any of the K values are smaller than 10^-3 then they are considered negligible.

Jesse Anderson-Ramirez 3I

Liquid water is not included in equilibrium concentration calculations.

Jesse Anderson-Ramirez 3I

Kp is for gases and uses partial pressure. Kc uses concentrations.

Jesse Anderson-Ramirez 3I

ICE is used when trying to the find the equilibrium concentrations.

Jesse Anderson-Ramirez 3I

H20 is not included when it is in liquid form.

Jesse Anderson-Ramirez 3I

You would use Kp because you would use pressure to find the equilibrium constant of gases.

Jesse Anderson-Ramirez 3I

K is a constant and is used when a reaction is in equilibrium. Q can be found at any point during a reaction and can be compared to K in order to find the direction of the reaction.

Jesse Anderson-Ramirez 3I

It depends on whether the reaction is going forward or reverse. This is found by comparing the reaction quotient (Q) and the chemical equilibrium (K).

Jesse Anderson-Ramirez 3I

Anything learned during the week should be the focus of the homework. Homework 3 should probably be on acid and base equilibria.

Jesse Anderson-Ramirez 3I

You would only use reactants and products that are in gas or aqueous phases when calculating the equilibrium constant.

Jesse Anderson-Ramirez 3I

R is the gas constant with a value of 8.314 (J)/((Mol)(K))

Jesse Anderson-Ramirez 3I

Q, the reactant quotient, is calculated the same way as K, but Q is not in equilibrium.

Jesse Anderson-Ramirez 3I

Since the equation involves gases you would need to use Kp and partial pressures.

Jesse Anderson-Ramirez 3I

When solving for Q you would leave out solids and liquids.

Jesse Anderson-Ramirez 3I

Since HCL is a strong acid, pH can be found by taking -log[HCL].

Jesse Anderson-Ramirez 3I

elements with room in their d-orbitals usually can disobey the octet rule.

Jesse Anderson-Ramirez 3I

Also, 10^-ph gives you the H+ concentration.

Jesse Anderson-Ramirez 3I

The Hydrogen must be bound to an F, O, or N.

Jesse Anderson-Ramirez 3I

I think you would use the same rules so your answer should match the lowest number of significant figures that were given in the question.

Jesse Anderson-Ramirez 3I

Should probably prioritize strong acids and bases but also work on the problems posted in the syllabus.

Jesse Anderson-Ramirez 3I

Bronsted acids and bases accept or donate protons while Lewis acids and bases accept or donate electron pairs.

Jesse Anderson-Ramirez 3I

Since NH4 has a full octet and doesn't want to accept any more electrons, it isn't considered a Lewis acid.

Jesse Anderson-Ramirez 3I

Water can act as either an acid or a base.

Jesse Anderson-Ramirez 3I

Osvaldo Sanchez Fernandez -4F wrote:You can start to approach this by simply knowing that the addition of pOH and pH Is equal to 14 so (pOH+pH=14). So if you find the pH of the molecule using the molarity you found in each problem you can just subtract it to 14 and get pOH or vice versa.

How do you solve for (c)?

Jesse Anderson-Ramirez 3I

The mass of an electron was provided on the formula sheet given out during midterm 1.

Jesse Anderson-Ramirez 3I

energy from the lamp = 32 J/s * 2s = 64J. Also 420nm should be converted to m (420 x 10^-9). Use the equation: E=hc/wavelength which gives you 4.73 x 10^-19 J per photon. Then 64/4.73 x 10^-19 gives you 1.4 x 10^20 J.

Jesse Anderson-Ramirez 3I

Usually your answer should match the lowest amount of significant figures given in the question.

Jesse Anderson-Ramirez 3I

You would use the lowest amount of sig figs present in the problem which is 3 because of the 100 kJ

Jesse Anderson-Ramirez 3I

The 1 is unnecessary.

Jesse Anderson-Ramirez 3I

Why can bond angles be slightly smaller than a given value? For example, why are some bond angles "slightly smaller" than 109.5?

Jesse Anderson-Ramirez 3I

Lone pairs repel other bonds and therefore cause the bond angles to decrease.

Jesse Anderson-Ramirez 3I

AX3E2 would be a T-shape with bond angles of 90 and 180.

Jesse Anderson-Ramirez 3I

Yes, the final is cumulative.

Jesse Anderson-Ramirez 3I

Maddie wrote:Will he give us the actual electronegativity values on the tests though?

Using trends, you need to know the electronegativity of atoms relative to other atoms.

Jesse Anderson-Ramirez 3I

I believe chemical bonds are part of the second test so yes, you can turn in work on chemical bonds.

Jesse Anderson-Ramirez 3I

Hydrogen bonding occurs when a hydrogen atom is covalently bound to an oxygen, fluorine, or nitrogen atom.

Jesse Anderson-Ramirez 3I

Anokhi Patel 4G wrote:what exactly is london dispersion?

LDF is the weakest of the intermolecular forces. LDF occurs when electrons in two adjacent atoms form temporary dipoles.

Jesse Anderson-Ramirez 3I

What type of molecules contain dipole-dipole interactions?

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