CHEMISTRY COMMUNITY

Emily Ng_4C

the ionic dissociation of water is given by the following reaction: the deltaH for the reaction is 58 kJ/mol. The Kw for the reaction at 25 degree Celsius is 10 ^-14. Is the pH of 7 acidic or basic at 10 degree Celsius?
2H20 --> H3O+ + OH-

Why is the answer acidic?

Emily Ng_4C

This is rare because H2O usually exists as the solvent and the concentration is too large to show any significant change.

Emily Ng_4C

the electrode goes on the outside while the anode is to the left and the cathode is to the right of the double lines (||), indicating a salt bridge. Species that are in the same phase are separated by a comma, while everything else is separated by a single line (|). I'm not sure what you mean by h+.

Emily Ng_4C

What is the logic behind choosing the model with the most linear graph as the rate order?

Emily Ng_4C

How can you tell what the order of each reactant is based on a table of rates and concentrations? Is there a formula or pattern?

Emily Ng_4C

Zero-order should be M/s. First-order should be s^-1. and second-order should be M^-1 * s^-1.

Emily Ng_4C

It is written that way because on the ride side of the double lines, which indicate a salt bridge, represents the cathode where reduction happens. The Cl2 is being reduced and gaining two electrons.

Emily Ng_4C

When you balance the half reactions and multiply the equations with a constant to get the same moles of electrons exchanged, it should be 6.

Emily Ng_4C

Make sure the number of atoms and the charges are equal on both sides.

Emily Ng_4C

What is the purpose and concept behind the Van't Hoff Equation?

Emily Ng_4C

Why do electrons flow from the anode to the cathode?

Emily Ng_4C

What is the purpose of the salt bridge?

Emily Ng_4C

A buffer is something that limits the change in pH in an acid-base reaction.

Emily Ng_4C

Specific heat capacity is for mass while molar heat capacity is for moles.

Emily Ng_4C

When you divide the pressures, the atm's cancel each other out. Your ending units should be J/ K.

Emily Ng_4C

Since delta H and delta U values can differ depending on the conditions the reaction is happening in, the degree symbol tells us that the reaction is happening under a standard condition of 1atm.

Emily Ng_4C

Entropy values are usually given to us in a table.

Emily Ng_4C

What is a microstate and how does it relate to entropy?

Emily Ng_4C

The temperature doesn't change because a phase change is happening. The heat being put into the system is causing the phase change and causing the molecules to overcome all the attractive forces, which allows a substance to go from solid to liquid and a liquid to a gas.

Emily Ng_4C

Method #3 is focused on the heat capacity, which is the heat required to raise the temp of an object by 1 degree C. The change in heat or enthalpy can be solved by this equation: qp = enthalpy = nCpdeltaT (The p's are subscripts). Cp represents the molar heat capacity at constant pressure. DeltaT is...

Emily Ng_4C

A state function means that we only care what happens at the beginning and at the end and it isn't dependent on the path taken. So, enthalpy is a state function because we can add and subtract heat to get the change in enthalpy.

Emily Ng_4C

Ka2 represents the second reaction that polyprotic compounds often go through. In this case, H2SO4's second reaction (HSO4- +H20 --> SO42- +H3O+) produces an insignificant amount of H3O+ that we ignore the second ionization.

Emily Ng_4C

Ka and Kb values should be given to us

Emily Ng_4C

For part b, the bond holding X2 together is broken to form 2X. Breaking bonds is an endothermic reaction that requires the absorbance of heat/energy.

Emily Ng_4C

If the Ka or Kb is greater than 10^3, then it is a strong acid or base. If the Ka or Kb is less than 10^-3, then it is a weak acid or weak base

Emily Ng_4C

Sometimes, the x is so small that it doesn't have an effect on the overall concentration. For instance, let's say the initial concentration is 1 x 10^-1 and the K value is extremely small, we would know that the numerator/reactants would also have to be extremely small so that the ratio will equal t...

Emily Ng_4C

Solids aren't included because they don't have a concentration. Liquids aren't included because they are usually solvents and don't change much in concentration throughout the reaction. Liquids would just show up on both sides of the equation and cancel each other out.

Emily Ng_4C

Miya Lopez 1I wrote:Also, what does it mean to be "completely ionized"?
In class Dr. Lavelle stated that "Ba(OH)₂ (aq) is a strong base, essentially completely ionized."

To completely ionized means to completely dissociate. For instance, BaOHsub2 will dissociate completely into Ba2+ and OH-

Emily Ng_4C

Percent ionization shows how much something dissociated. It can be calculated by taking the concentration of its ions divided by the original compound and multiplied by 100. For instance, weak acids will have a varying percent ionization because only a small percent of it will dissociate. Percent io...

Emily Ng_4C

Q shows whether the reaction will move more to the right or to the left, producing either more products or reactants. For instance, if Q<K, then the reaction will shift toward the right. This will produce more products and eventually, Q will equal K.

Emily Ng_4C

R is the gas constant and it is important to note that it differs depending on whether atm, torr, or bar is used for the pressure unit.

Emily Ng_4C

Solids are not included because they don't have a concentration because solids are usually pure. Liquids are not included because they usually exist as a solvent and thus has such a large concentration that it barely changes throughout the reaction.

Emily Ng_4C

S-character is the ratio of the S to the P. For instance, an sp hybrid orbital would have a 1:1 and sp2 would be 1:2. And so, sp would have more s-character than sp2.

Emily Ng_4C

What are all the elements that have latin names do we need to know?

Emily Ng_4C

Do we end all names of anions with an -ate even if the overall charge or the anion is not negative?

Emily Ng_4C

Sigma bonds are when two orbitals bond at one point, while pi bonds are when two orbitals bond at two points.

Emily Ng_4C

When you see an OH in a molecular formula, the H usually goes on the O. However, to be sure, calculate the formal charges and make sure it aligns with how you are drawing the molecules.

Emily Ng_4C

A molecule is polar when the electron distribution is not equal and the dipole moments do not cancel out. However, when thinking about whether a molecule is polar or not, it is important to think of it in 3-D. For instance, CCl4 is tetrahedral and nonpolar.

Emily Ng_4C

Hydrogen Bonding is a specific dipole-dipole bonding. H-Bonding only occurs between Hydrogen and Fluorine, Oxygen, or Nitrogen.

Emily Ng_4C

The energy will be between the orbitals because it is an average of the orbitals that are hybridizing.

Emily Ng_4C

Hybridization occurs molecules/atoms can bond with other molecules/atoms. To my understanding, looking at the electronic configuration, electrons aren't always in the spot to bond. For instance, carbon's electronic configuration is 1s22s22p2. It only has 2 unpaired electrons even though we know that...

Emily Ng_4C

I would suggest memorizing the basic angles like tetrahedral is 109.5, trigonal planar is 120, and linear is 180. Then, you should understand how lone pairs affect those angles. Lone pairs push the bonded atoms together making the angles smaller. For instance, a trigonal pyramidal is <109.5.

Emily Ng_4C

All those intermolecular forces are the same, so you should be able to name that force with whichever name.

Emily Ng_4C

Polarizability is how much the electrons in an atom can be distorted. For example, atoms with more electrons tend to be more polarizable.

Emily Ng_4C

What are the purposes of sigma and pi bonds? Do they just create a bigger area for electron movement? I believe sigma and pi bonds give you a more specific visual representation of how two atoms/molecules bond. For instance, sigma bond is where they bond at one point, and a pi bond is where they bo...

Emily Ng_4C

Sigma and Pi bond tell you more specifically how two atoms/molecules bond. For instance, a sigma bond is where two atoms/molecules bond at one point, while a pi bond is where two atoms/molecules bond at two points.

Emily Ng_4C

HCl has a permanent dipole because Cl is one of the most electronegative element while H isn't. So, Cl has the tendency to pull all the electron, creating a dipole.

Emily Ng_4C

The more electrons a molecule has, the more polarizable it is. Because there are more dispersion forces happening in larger molecules because of the number of electrons, the interactions are likely to be a liquid substance over a gaseous substance. This is evident in why F2 is a gas and Br2 is a liq...

Emily Ng_4C

Molecules can be neutral/nonpolar because all the electrons are orienting themselves around the central atom evenly. However, since they still have electrons, the electrons move around, creating a temporary dipole moment that interacts with other molecules with a temporary dipole moment.

Emily Ng_4C

The ionization energy increases because there is a stronger positive nuclear charge that pulls the electron towards the center. In addition, as there are more electrons in one cloud, the more it wants to fill up the octet rather than getting rid of the electrons.

Emily Ng_4C

You want each individual atom to be as close to zero as possible, but the overall formal charges should add up to the charge of the molecule.

Emily Ng_4C

Yes, the more negative atom will be the more electronegative atom since they want to attract electrons to fill their outer shell.

Emily Ng_4C

(NH4)2+ and (SO4)2- are cations and anions which form an ionic bond through the transferring of electrons.

Emily Ng_4C

You base it off of the group the elements are in. For example, Group 1 would have 1 valence electron. However, the transition metals will vary in how many valence electrons they will have.

Emily Ng_4C

Yes. For example, if an element has a high ionization energy, it is less likely to have an electron removed. Rather, it would accept electrons to meet the octet rule. Vice versa as well.

Emily Ng_4C

No, I don't think anything is faster than the speed of light.

Emily Ng_4C

I think the lyman and balmer series are the only ones we need to know. Lyman series is when an electron drops back down to n=1 while Balmer is when an electron drops back down to n=2.

Emily Ng_4C

Why is there a negative in E=-hR/n^2?

Emily Ng_4C

What does it mean for something to be quantized?

Emily Ng_4C

Threshold energy is the minimum amount of energy needed to eject an electron

Emily Ng_4C

For combustion reactions, a hydrocarbon is usually reacted with oxygen to form water and carbon dioxide. To arrange reactants and products, you need to know what is actually going on in the reaction and what type of reaction it is.

Emily Ng_4C

Writing out the units usually helps with understanding what the next step is. For example, molar mass is g/mol and to find the number of mols for a certain mass. You would take the mass and divide it by the molar mass. This would cancel out the grams.

Emily Ng_4C

The amount of product the limiting reactant produces will be the actual yield because you can't produce more if there is not enough of one of the parts.

Emily Ng_4C

You can convert the mass of CaCO3 to moles and then use the mole to mole ration from the chemical equation to find the moles of CO2.

Emily Ng_4C

Combustion requires the presence of O2 and will always form H2O and CO2.

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