CHEMISTRY COMMUNITY

Sukanya Mohapatra 2G

It can be used with any reaction orded

Sukanya Mohapatra 2G

Pretty sure you can email and ask your TA!

Sukanya Mohapatra 2G

Why are the most common heterogeneous catalysts finely divided or porous solids?

Sukanya Mohapatra 2G

No, but it may affect the amount of time a reaction needs to take place.

Sukanya Mohapatra 2G

A is the pre-exponential factor. According to collision theory, A is the frequency of collisions in the correct orientation.

Sukanya Mohapatra 2G

The activation energy of a reaction is measured in joules (J), kilojoules per mole (kJ/mol) or kilocalories per mole (kcal/mol)

Sukanya Mohapatra 2G

Yes, the rate would depend on the slowest step.

Sukanya Mohapatra 2G

A larger K does indicate a faster reaction.

Sukanya Mohapatra 2G

They are determined according to experimental data.

Sukanya Mohapatra 2G

If we are told that a reaction is the slow step in a mechanism, can we assume its reverse is slow enough to be ignored? Or should we be told that explicitly

Sukanya Mohapatra 2G

A Galvanic cell converts chemical energy into electrical energy. An electrolytic cell converts electrical energy into chemical energy.

Sukanya Mohapatra 2G

Galvanic and voltaic cells are the same thing, but with different names. However, in comparison to galvanic cells, electrolytic cells convert electrical energy into chemical energy while galvanic cells convert chemical energy into electrical energy.

Sukanya Mohapatra 2G

The standard hydrogen electrode is a redox electrode which forms the basis of the thermodynamic scale of oxidation-reduction potentials. Potentials of any other electrodes are compared with that of the standard hydrogen electrode at the same temperature.

Sukanya Mohapatra 2G

An oxidizing agent, or oxidant, gains electrons and is reduced in a chemical reaction. A reducing agent, or reductant, loses electrons and is oxidized in a chemical reaction.

Sukanya Mohapatra 2G

When drawing a cell diagram, the anode is placed on the left side while the cathode is placed on the right side.

Sukanya Mohapatra 2G

The purpose of the salt bridge is to maintain charge balance because the electrons are moving from one-half cell to the other.

Sukanya Mohapatra 2G

I think it's important to remember that the larger the molar mass, the greater the complexity which causes higher entropy.

Sukanya Mohapatra 2G

An isobaric expansion of a gas requires heat transfer to keep the pressure constant.

Sukanya Mohapatra 2G

Van't hoff is derived from ΔG=ΔH−TΔS and ΔG= -RTlnK. The Van 't Hoff equation relates the change in the equilibrium constant, Keq, of a chemical reaction to the change in temperature, T, given the standard enthalpy change, ΔH.

Sukanya Mohapatra 2G

I don't think you need to memorize the derivations as long as you know how to use the equations given on the sheet.

Sukanya Mohapatra 2G

They are synonyms of one another.

Sukanya Mohapatra 2G

The standard entropy of a substance increases with an increase in the molar mass. This is because with the increase in molar mass the energy states of the atoms are more closely spaced to each other. Due to more closely spacing between the energy states, there is greater dispersal of energy at the g...

Sukanya Mohapatra 2G

Microstates is a term used to describe the number of different possible arrangements of molecular position and kinetic energy at a particular thermodynamic state. A process that gives an increase in the number of microstates increases the entropy.

Sukanya Mohapatra 2G

Positional entropy refers to the number of molecular positions or arrangements that a system can have, while thermal entropy refers to the amount of thermal energy that is not available for any useful work.

Sukanya Mohapatra 2G

The Van 't Hoff equation relates the change in the equilibrium constant, Keq, of a chemical reaction to the change in temperature, T, given the standard enthalpy change, ΔH for the process.

Sukanya Mohapatra 2G

Yes, it is possible for isothermal reactions to be irreversible.

Sukanya Mohapatra 2G

In a irreversible reaction, the reactants react to form the products, which cannot revert back into reactants. In reversible reactions, as the reactants react with other reactants to form products, the products are reacting with other products to form reactants.

Sukanya Mohapatra 2G

In this formula, we are looking at changes in entropy.

Sukanya Mohapatra 2G

A decrease in the number of moles on the product side means lower entropy. An increase in the number of moles on the product side means higher entropy. If the reaction involves multiple phases, the production of a gas typically increases the entropy much more than any increase in moles of a liquid o...

Sukanya Mohapatra 2G

I believe it is given.

Sukanya Mohapatra 2G

Delta U would equal delta H when work is equal to 0.

Sukanya Mohapatra 2G

A negative delta H would be exothermic.

Sukanya Mohapatra 2G

Hess's Law states that regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of all changes.

Sukanya Mohapatra 2G

When steam comes into contact with skin, it condenses since the skin is at a lower temperature. The process of condensation releases energy (as heat) which causes the burn. Since the water is going through a phase change, the temperature of the steam is not getting lower even though energy is being ...

Sukanya Mohapatra 2G

You only count the coefficients of gaseous molecules.

Sukanya Mohapatra 2G

The change in enthalpy for a given reaction will be the combined total of the energy required to break any bonds that are broken and the energy released from any bonds that are formed.

Sukanya Mohapatra 2G

Due to Le Chatelier's Principle, the reaction would want to minimize pressure and would thus shift to the side with fewer moles.

Sukanya Mohapatra 2G

You would need to use an ICE table and then equate to K to solve for X.

Sukanya Mohapatra 2G

If not given additional info, either can be used since they represent the same quantity.

Sukanya Mohapatra 2G

Gases are most ideal at high temperature and low pressure so under these conditions the ideal gas law is more accurate. Under differing conditions, the ideal gas law is more of an approximation.

Sukanya Mohapatra 2G

Divide X by initial concentration and then multiply by 100 to get the percentage.

Sukanya Mohapatra 2G

The combined gas law is useful when given two pressures, volumes, or temperatures and asked for an unknown pressure, volume, or temp.

Sukanya Mohapatra 2G

After converting units, use the ideal gas law.

Sukanya Mohapatra 2G

If you get two positive X values, you should plug them back in to ensure the right answer gives a positive value when subtracted from initial concentration.

Sukanya Mohapatra 2G

If the concentration from the addition of an acid is very small, then it will not affect the pH that much. So autoprotolysis will be the determining factor in the pH.

Sukanya Mohapatra 2G

I believe most of the unit conversions will be provided on the formula sheet.

Sukanya Mohapatra 2G

I think it might be helpful to understand the concepts behind the other laws, since it would help you remember the individual relationships between variables of the ideal gas law.

Sukanya Mohapatra 2G

A gas behaves more like an ideal gas at higher temperature and lower pressure, since the potential energy due to intermolecular forces becomes less significant compared with the particles' kinetic energy, and the size of the molecules becomes less significant compared to the empty space between them.

Sukanya Mohapatra 2G

These topics may be covered later, but as of now, they haven't been discussed in class.

Sukanya Mohapatra 2G

Pa stands for Pascal and 100,000 Pascals is equal to one bar.

Sukanya Mohapatra 2G

You can do so by writing out the reaction for the salt and analyzing the products.

Sukanya Mohapatra 2G

Find the molarity and then plug into the pH equation.

Sukanya Mohapatra 2G

Ligands act as Lewis bases (electron pair donors), and the central atom acts as a Lewis acid (electron pair acceptor). Ligands have at least one donor atom with an electron pair used to form covalent bonds with the central atom.

Sukanya Mohapatra 2G

pKa = -log [Ka]. pH = - log [H+] Ka and Kb are related to each other through the ion constant for water, Kw with equation Kw = Ka x Kb.

Sukanya Mohapatra 2G

Strong acids completely dissociate in their aqueous solutions. Thus the degree of dissociation is 100% which means Ka will be infinity after some time, which is why pKa is used mostly for weak acids.

Sukanya Mohapatra 2G

The formula for pH is pH = -log[H+]. This means pH is the negative base 10 logarithm of the hydrogen ion concentration of a solution. To calculate it, take the log of the hydrogen ion concentration and reverse the sign to get the answer.

Sukanya Mohapatra 2G

Also, acids change litmus paper red while bases change litmus paper blue.

Sukanya Mohapatra 2G

In chemistry, a base is a chemical species that donates electrons, accepts protons, or releases hydroxide (OH-) ions in aqueous solution. Types of bases include Arrhenius base, Bronsted-Lowry base, and Lewis base.

Sukanya Mohapatra 2G

The sigma p bonding orbital is the lowest energy orbital which means it will have zero nodes. Then there is the pi bonding orbitals (1 node), the pi anti-bonding orbitals (2 nodes) and finally the anti-bonding sigma p orbital which has three nodes.

Sukanya Mohapatra 2G

A dative covalent bond, or coordinate bond, is a bond where there is 1 pair of shared electrons between two atoms. The difference relative to a covalent bond is that in a dative covalent bond these electrons both come from one atom.

Sukanya Mohapatra 2G

Additionally, the strength of an acid can be measured by its position on the pH scale.

Sukanya Mohapatra 2G

Hybridization occurs everytime there are multiple electron domains.

Sukanya Mohapatra 2G

The bond angle would increase when the s character increases because there is a decrease in the p character, which would mean less electron densities around the central atom.

Sukanya Mohapatra 2G

Valence bond theory describes the electronic structure of molecules. The theory says that electrons fill the atomic orbitals of an atom within a molecule. It also states that the nucleus of one atom is attracted to the electrons of another atom.

Sukanya Mohapatra 2G

EDTA is used to bind metal ions in the practice of chelation therapy, such as for treating mercury and lead poisoning. It is used in a similar manner to remove excess iron from the body.

Sukanya Mohapatra 2G

Yes, you should be more concerned with the octet rule first.

Sukanya Mohapatra 2G

Generally, what matters more is that your lewis structure is stable. Typically, the structure with the most formal charges on the atoms closest to zero is the more stable Lewis structure.

Sukanya Mohapatra 2G

There can only be one sigma bond but multiple pi bonds.

Sukanya Mohapatra 2G

Sigma bonds are end to end interactions that allow the atom to rotate around the internuclear axis and pi bonds are overlapping side by side bonds that don't allow atoms to rotate. There can only be one sigma bond between two atoms while there can be more than one pi bond.

Sukanya Mohapatra 2G

If there is a pi bond present means that there is also a sigma bond present,making the bond strength stronger. Also, pi bonds will bond side by side, so if the atoms rotate, the pi bonds will break.

Sukanya Mohapatra 2G

Since electronegativity is the tendency of an atom to attract a shared pair of electrons towards itself, greater ionic character implies a greater difference in electronegativities.

Sukanya Mohapatra 2G

The speed of light is 3.0 x 10^8 m/s while the frequency can be determined according to wavelength.

Sukanya Mohapatra 2G

It is a covalent bond in which both shared electrons are donated by the same atom

Sukanya Mohapatra 2G

This is because of an electron being added to an already half full orbital in oxygen, which results in electron-electron repulsion,lowering the ionization energy.

Sukanya Mohapatra 2G

Bond length is determined by bond order, thus the higher the bond order, the shorter the bond length.

Sukanya Mohapatra 2G

Metallic elements tend to be lustrous, ductile, malleable, can conduct electricity, and tend to form cations in aqueous solutions. Nonmetals are non-lustrous, brittle, poor conductors, and tend to form anions in solutions.

Sukanya Mohapatra 2G

Yes, it is an average

Sukanya Mohapatra 2G

Electron distortion occurs when the electrons of the anion are attracted to the cation, causing the shape of the electron density to change slightly.

Sukanya Mohapatra 2G

Induced dipoles can occur when one molecule with a permanent dipole repels another molecule's electrons.

Sukanya Mohapatra 2G

Electronegativity is the likelihood of an atom to attract electrons, and electron affinity is the amount of energy released when an electron is added to a neutral atom.

Sukanya Mohapatra 2G

Delocalized electrons are electrons in a molecule or ion that aren't associated with a single atom or a covalent bond. It occurs when electric charge is spread over more than one atom.

Sukanya Mohapatra 2G

I would use dots instead of lines to keep things clear and avoid confusion.

Sukanya Mohapatra 2G

They are used to predict the behavior of molecules in molecular orbital theory, which describes the electronic structure of molecules.

Sukanya Mohapatra 2G

H and He are exceptions to the octet rule since their full shell is two electrons. Li and Be are metals, making them more likely to lose electrons and turn into cations.

Sukanya Mohapatra 2G

The bond length is the average distance between the nuclei of two bonded atoms in a molecule. It is an average due to a bond not being a static structure, but instead one in which atoms vibrate because of thermal energy.

Sukanya Mohapatra 2G

Can someone explain the Aufbau Principle in greater detail?

Sukanya Mohapatra 2G

They are exceptions because they do not follow the normal electron configuration pattern. This is because a completely full or half full d sub-level is more stable than a partially filled d sub-level, so an electron from the 4s orbital is excited and rises to a 3d orbital.

Sukanya Mohapatra 2G

A completely full or half full d sub-level is more stable than a partially filled d sub-level, so an electron from the 4s orbital is excited and rises to a 3d orbital.

Sukanya Mohapatra 2G

Why were silver atoms used in the experiment, as opposed to other atoms?

Sukanya Mohapatra 2G

What are nodal planes and how are they relevant to orbital shapes?

Sukanya Mohapatra 2G

They were developed in the 1920s, during the time period the phrase "quantum mechanics" was coined.

Sukanya Mohapatra 2G

This is based on ionization energy, which is the amount of energy required to remove an electron from an atom.

Sukanya Mohapatra 2G

Light does not have mass, so the DeBroglie equation would not work.

Sukanya Mohapatra 2G

There are four quantum numbers which include the principal quantum number (n), the angular quantum number (l), the magnetic quantum number (m), and the spin quantum number (s). When electrons are added to atoms, they take the lowest available value of n. Also, all orbitals in a subshell must have on...

Sukanya Mohapatra 2G

How is x-ray crystallography used to determine structure?

Sukanya Mohapatra 2G

I have a hard time memorizing prefixes, especially ones that aren't as common. Is there any way to remember them more effectively?

Sukanya Mohapatra 2G

For class, is it necessary to memorize the electromagnetic spectrum, along with its respective frequencies and wavelengths?

Sukanya Mohapatra 2G

Do the values of the molar masses we use for calculations affect the number of significant figures the answer contains?

Sukanya Mohapatra 2G

Formula weight is the sum of the atomic weights of the atoms in its empirical formula. Molecular weight is a molecule's average mass as calculated by adding together the atomic weights of the atoms in the molecular formula. Atomic weight is the mass of one mole of the given element.

Sukanya Mohapatra 2G

How does assigning oxidation numbers help you balance chemical equations? I saw my TA use it for a problem during discussion but wasn't able to get clarification. Thanks.

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