CHEMISTRY COMMUNITY

Hadji Yono-Cruz 2L

You only draw the curved arrows when asked for the mechanism.

Hadji Yono-Cruz 2L

Should we remember all of the functional groups mentioned in the slide in lecture?

Hadji Yono-Cruz 2L

Try to remember the structures and how to identify them.

Hadji Yono-Cruz 2L

Alyssa Wilson 2A wrote:I believe one of the TA's will be holding a review session next week where they will be going through the entire test.

Where and when is this review session being held?

Hadji Yono-Cruz 2L

You add Pt when there are no conducting solids in the cell diagram. Also, you can use graphite as well but Pt is more common in the textbook.

Hadji Yono-Cruz 2L

Yes, understanding phase changes is beneficial and it is important to note that temperature is constant during a phase change.

Hadji Yono-Cruz 2L

When cell potential is positive then the forward reaction is spontaneous. When the cell potential is negative then the forward reaction is nonspontaneous.

Hadji Yono-Cruz 2L

Platinum is used when there is no conducting metal on either or both sides of the redox reaction. Another used electrode can be graphite, but platinum is most common in the textbooks.

Hadji Yono-Cruz 2L

The more negative the E cell, then the stronger the reducing agent.

Hadji Yono-Cruz 2L

Use whichever the question is asking for, but if you are not given the molar heat capacity then convert the moles into grams and use specific heat capacity.

Hadji Yono-Cruz 2L

You can use mass x delta H of phase change or number of moles x delta H of phase change depending on what you are given.

Hadji Yono-Cruz 2L

There would not be change because matter and energy is not exchanged between an isolated system and its surroundings.

Hadji Yono-Cruz 2L

In an isothermal reaction then delta U is zero.

Hadji Yono-Cruz 2L

Q and K are calculated in the same way. Q is calculated at any point of the reaction, but K is calculated only at equilibrium. If Q is less than K then the products are favored. If Q is less than K then the reactants are favored.

Hadji Yono-Cruz 2L

Brackets means that the K is Kc and should be in terms of concentration. P means that K is Kp and should be in terms of partial pressure.

Hadji Yono-Cruz 2L

For a reversible reaction, you use w=-nRT ln (v2/v1) and for an irreversible reaction, you use w=-Pex times delta V.

Hadji Yono-Cruz 2L

I know boltzman equation is S= k ln W, but when am I supposed to use S= R Ln W ( k times avogadro's number is R)?

Hadji Yono-Cruz 2L

They can have both be constant or changing.

Hadji Yono-Cruz 2L

The question is asking what is the standard enthalpy formation of N2O5, not the overall reaction. From the chemical equation, O2 is in its natural state, so the enthalpy for O2 is 0. We are also given the standard enthalpy of formation for NO which is 90.25 KJ. With this information we know that del...

Hadji Yono-Cruz 2L

Q and K are calculated the same way (products/reactants), but Q can be measured at any point of the reaction and K is only measured at equilibrium. If Q < K then the forward reaction is favored. If Q > K then the reverse reaction is favored.

Hadji Yono-Cruz 2L

If you shift the partial pressure of the product, then equilibrium will shift to the reactants. If you shift partial pressure of a reactant, then equilibrium will shift towards the products. If you introduce an inert gas that is not involved in the chemical reaction then equilibrium will remain unch...

Hadji Yono-Cruz 2L

An increase in pressure means a decrease in volume, so equilibrium will shift to the side where there are less moles of gas.

Hadji Yono-Cruz 2L

When a reaction vessel has an inert gas pumped into it at a constant volume to increase the total pressure, then the total pressure will increase but the partial pressures of the reactants and products are unchanged and therefore the K value will not be affected.

Hadji Yono-Cruz 2L

As long as there is no change in volume, then equilibrium will not be shifted because the inert gas is not included in the chemical reaction.

Hadji Yono-Cruz 2L

Solids and liquids do not compress or expand, so their volume does not change.

Hadji Yono-Cruz 2L

Delta H is the change in enthalpy and q represents heat.

Hadji Yono-Cruz 2L

I did the same thing as explained above and I get Kc=[BrCl]^2/[Br2][Cl2]=[3.37 x 10^-5]^2/[7.52 x 10^-5][7.52 x 10^-5]. My answer: 0.199637845, however, is not an answer choice can someone please explain what I did wrong? Thank you! I made this mistake as well. The question should be answered in te...

Hadji Yono-Cruz 2L

When determining the moles of the reaction in terms of pressure, do we include the number of moles of solids and liquids in the reaction or just the gases?

Hadji Yono-Cruz 2L

Removing products would only affect Q because only temperature causes the K value to change.

Hadji Yono-Cruz 2L

If pressure increases then that means volume decreases, so reaction will shift toward the side with less gas moles.

If pressure decreases then that means volume increases, so reaction will shift toward the side with more gas moles.

Hadji Yono-Cruz 2L

5% refers to the x value and if it is less than 5% then x will be insignificant to calculations, so the quadratic formula would not have to be used and you can simply plug in the values that are given.

Hadji Yono-Cruz 2L

For endothermic reactions: If temperature increases, then the forward reaction is favored. If temperature decreases, then the reverse reaction is favored. For exothermic reactions: If temperature increases, then the reverse reaction is favored. If temperature decreases, then the forward reaction is ...

Hadji Yono-Cruz 2L

K=1 is rare because there is a 1:1 ratio of reactants to products and that is usually never seen in real life applications.

Hadji Yono-Cruz 2L

Kp cannot be used in place for Kc, but you can convert one into the other by using the formula: Kp= Kc(RT)^delta n. Delta n is equal to the moles of the products minus the moles of the reactants. This formula relates Kp to Kc, so you can convert one to the other.

Hadji Yono-Cruz 2L

For most problems R and T are constants and will be given in the problem. This formula is generally used to find pressure or concentration.

Hadji Yono-Cruz 2L

You can add the bond lengths together and divide by the total amount of resonance structures to find the average bond length.

Hadji Yono-Cruz 2L

These are the same.

Hadji Yono-Cruz 2L

s-character is the contribution of the sigma type bond in hybridization So, if you have sp, it is a 50-50 percent s-p character ratio, while sp2 has a ratio of 33-66 and sp3 has a ratio of 25 to 75 s character to p character. It's simply the percent that the s takes up in hybridization. This is cor...

Hadji Yono-Cruz 2L

A C=C double bond is stronger than a single bond but it is weaker than the sum of 2 single C-C bonds. Sigma bonds are harder to break than pi bonds because sigma bonds have their overlap closer to both of the atom's nuclei and the electrons are more attracted to the nuclei because of the positive ch...

Hadji Yono-Cruz 2L

The bent shape comes from the lone electron pair because that region counts as an area of electron density. That lone pair causes a repulsion for the other electrons which push the other bond angles closer together.

Hadji Yono-Cruz 2L

Just to be clear, when we draw lewis structures we draw the electrons of the atoms, but when we draw the VSEPR model we do not include the electrons? We only include the shared electrons?

Hadji Yono-Cruz 2L

Thanks Joyce!

Hadji Yono-Cruz 2L

What is the difference between a coordinate covalent bond and covalent bond? How can you identify if a molecule has a coordinate covalent bond or a covalent bond?

Hadji Yono-Cruz 2L

Round your answer at the end to avoid errors in your calculations beforehand.

Hadji Yono-Cruz 2L

You can use either of the products to find the limiting reactant. Just make sure that you use the same product (does not matter which you choose) when comparing the reactants. However, on a test the next subquestion might ask about a specific product, so it may be more beneficial to choose that one ...

Hadji Yono-Cruz 2L

Sigma bonds head-on overlap puts the electron closer to the other atom's nucleus. The pi bonds overlap does not put the electron as close in comparison to the sigma bond, so the sigma bond is stronger.

Hadji Yono-Cruz 2L

Yes they can, if the combined mass of the empirical formula is the same as the molecular mass given then they are the same.

Hadji Yono-Cruz 2L

Pi bonds would break first because their electrons are more spread out than those of sigma bonds. The electrons in a sigma bond are directly between the two nuclei and are harder to break.

Hadji Yono-Cruz 2L

How can you tell what atom has a shorter or longer bond length when comparing atoms and ions? For example, rank the molecules from smallest to largest N-O bond length.

NO2-, NO3-, NO+, NO

Hadji Yono-Cruz 2L

Can someone explain the reasons behind the trends we see in the periodic table? - Atomic radius - Ionization energy - Electronegativity How do they relate to shielding effect and number of electrons or protons? Atomic radius increases going down the periodic table because a valence electron is adde...

Hadji Yono-Cruz 2L

Since both ionization energy and electronegativity are the energies to remove an electron, then what is the difference between them? Does ionization energy refer only to ionic bonds and electronegativity refers to covalent bonds?

Hadji Yono-Cruz 2L

Why do Cu and Cr not follow the same trend of writing the electron configuration as other atoms?

Hadji Yono-Cruz 2L

What are some methods for studying for the midterm that people have found helpful?

Hadji Yono-Cruz 2L

I do not understand the importance of degeneracy.

Hadji Yono-Cruz 2L

Ahhh thank you for the explanation.

Hadji Yono-Cruz 2L

Ok so to start off we have to find out how much grams of KNO3 are in the sample of 510 g The first step is to to get 5.45 from a percentage to a decimal so we divide it by 100 and it becomes .0545. Then we multiply .0545 by the 510 g to get how much grams of KNO3 were in this aqueous solution which...

Hadji Yono-Cruz 2L

1.7 (a) The frequency of violet light is 7.1 " 1014 Hz. What is the wavelength (in nanometers) of violet light? (b) When an electron beam strikes a block of copper, x-rays with a frequency of 2.0 " 1018 Hz are emitted. What is the wavelength (in picometers) of these x-rays. The answer for ...

Hadji Yono-Cruz 2L

Electromagnetic radiation is another word for energy propagated through free space or through a material medium in the form of electromagnetic waves. Therefore, we can think of this as light since it is a type of electromagnetic wave. Looking at the equation for energy per photon of light, E = h\nu...

Hadji Yono-Cruz 2L

What are some effective ways to study for chemistry?

Hadji Yono-Cruz 2L

These are very helpful! Thank you!

Hadji Yono-Cruz 2L

First, you must convert the 2.50 t of NaBr to grams using the conversion factor 1.0 x 10^6 grams = 1 ton. Then you find the molar mass of NaBr (102.89g) and divide the grams of NaBr by NaBr's molar mass. Next, find the mole ratio between Fe and NaBr which is 3 mol Fe: 8 mol NaBr (don't forget to ma...

Hadji Yono-Cruz 2L

I asked the guy sitting next to me if he had any Sodium Hypobromite
He said NaBrO

Hadji Yono-Cruz 2L

Adding on from other people's suggestions, look up Tyler Dewitt on Youtube. He is really good at teaching chemistry and helped me get through my AP chemistry class in high school.

Hadji Yono-Cruz 2L

When using significant figures, do you use significant figures throughout your whole calculation (for example if the given significant figures is 2, but I am using molar mass and the molar mass contains 4 significant figures then do I change the molar mass to 2 significant figures or leave as is) or...

Search found 64 matches