CHEMISTRY COMMUNITY

Nathan Mariano 2G

Is steady state equilibrium going to be on the final?

Nathan Mariano 2G

The heat capacity of water is 4.184 J • C^-1 g^-1 or 4.184 J • K^-1 g^-1. Why is the heat capacity of water per celsius and per Kelvin the same? I thought that the conversion rate between Celsius and Kelvin is +273 K.

Nathan Mariano 2G

When is Ka2 considered negligible when performing calculations with polyprotic acids?

Nathan Mariano 2G

Use the information in Table 11.2 to determine the value of K at 300 K for the reaction 2 BrCl(g) + H2(g) <-> Br2(g) + 2 HCl(g). When combining K values, why must you multiply?

Nathan Mariano 2G

"If one starts with higher concentrations of reactants, the equilibrium concentrations of the products will be larger." Why is this statement true? Can there be a case where the equilibrium concentration of the product is smaller than the initial concentration of the reactants?

Nathan Mariano 2G

What is the difference between first-order reactions and second-order reactions? How does that change the value of n?

Nathan Mariano 2G

When balancing the half reaction in 14.11 O2 > OH-, how do you come to the conclusion that the reaction is occurring in a basic solution when not given that information?

Nathan Mariano 2G

Does the order of the species inside of the anode and cathode matter? For example, is the species before oxidation placed first and the species after it has been oxidized placed next?

Nathan Mariano 2G

Does the order of the species in the cell diagrams matter? Besides the fact that the right side is the cathode and the left side is the anode.

Nathan Mariano 2G

Why is standard residual entropy negative or a smaller number than standard molar entropy when the number of moles of gas is reduced?

Nathan Mariano 2G

What is the difference between Molar Entropy and Standard Residual Entropy?

Nathan Mariano 2G

What is the difference between Gibbs free energy of formation and Gibbs free energy of reaction conceptually? Does the way in which they are calculated differ?

Nathan Mariano 2G

What is the function of a salt bridge in a galvanic cell? How would the galvanic cell react without a salt bridge?

Nathan Mariano 2G

How do you measure Gibbs Free Energy experimentally? (Without the use of the equation)

Nathan Mariano 2G

In order for a spontaneous reaction to occur, delta G must be negative. For a spontaneous reaction to occur, delta H must be negative and delta S must be positive. For a nonspontaneous reaction to occur, delta H must be positive and delta S must be negative.

Nathan Mariano 2G

Dr. Lavelle mentioned that a positive delta H (endothermic reaction) is, the more that it does not favor the forward process in the equation (delta g = delta h - temperature x delta s). Why does a positive delta H not favor the forward process? I thought that endothermic reactions do favor forward r...

Nathan Mariano 2G

If Gibbs Free Energy (Delta G) is not measured directly like enthalpy of formation (Delta H), how is the Delta G of a reaction measured experimentally?

Nathan Mariano 2G

In what instances do we need to convert Celsius to Kelvin when calculating heat released (q)? In 8.19, Celsius is not converted into Kelvin.

Nathan Mariano 2G

8.51 The enthalpy of formation of trinitrotoluene (TNT) is -67 kJ·mol^-1, and the density of TNT is 1.65 g·cm^-3. In principle, it could be used as a rocket fuel, with the gases resulting from its decomposition streaming out of the rocket to give the required thrust. In practice, of course, it wo...

Nathan Mariano 2G

The first law of thermodynamics states that energy is neither created nor destroyed, therefore the overall amount of heat (q) needs to be the same. system + surroundings = universe In heat transfer, if one substance X is losing heat to another substance Y, then substance Y must be gaining the heat ...

Nathan Mariano 2G

When performing heat transfer problems, why is heat that is lost a positive q value and why is heat that is gained a negative q value?

Nathan Mariano 2G

In the example where Dr. Lavelle demonstrated the combustion of glucose, how can we assume that the pressure is constant?

Nathan Mariano 2G

How can we determine whether the work is performed by or on the system? What makes work positive or negative in terms of the system?

Nathan Mariano 2G

What was Dr.Lavelle referring to with the analogy of the boulder? The boulder is able to go down a hill without work, but for the boulder to go up a hill work is required. Can someone explain this in further detail?

Nathan Mariano 2G

The 5% rule allows one to ignore the x in the denominator if the equilibrium constant is less than 10^-3 when performing ICE table calculations. The change in concentration (x) must be less than or equal to 5% of the initial concentration. If the change in concentration (x) is greater than 5%, then ...

Nathan Mariano 2G

How do we determine which bonds are broken and formed using bond enthalpies?

Nathan Mariano 2G

H2SO4 is a strong acid and is fully ionized. Therefore, if the concentration of H2SO4 is 0.15 M, then the concentration of HSO4- and H3O+ would both have a concentration of 0.15 M.

Nathan Mariano 2G

While doing polyprotic acids and base calculations, what approximation justifies ignoring the second deprotonations?

Nathan Mariano 2G

If volume (V) decreases and pressure (P) increases and there are more moles of gas on the left, why does the reaction shift to the right? If there are more moles of gas on the right, why does the reaction shift to the left?

Nathan Mariano 2G

Introducing an inert gas in a chemical equilibrium will change the volume and the pressure of the vessel that the reactants and products occupy. However, the inert gas will not change the concentration/partial pressure of the reactants and products and therefore will not affect the chemical equilibr...

Nathan Mariano 2G

X is negligible when the equilibrium constant/acid dissociation constant (Ka)/base dissociation (Kb) constant is smaller than 10^-3. Also, as repeated above, X is negligible when it is less than 5% of the initial concentration.

Nathan Mariano 2G

How can we determine whether an acid/base reaction will favor the forward reaction or the reverse reaction? Why do acids favor forward reactions, while bases favor reverse reactions?

Nathan Mariano 2G

What is the effect of adding an inert gas to a system at equilibrium compared to using a piston to reduce the volume of the gases at equilibrium?

Nathan Mariano 2G

Pure liquids and pure solids are able to react in chemical reactions. Therefore, I do not completely understand the reason why pure liquids and pure solids are not contained in the equilibrium constant. Can someone explain this to me?

Nathan Mariano 2G

Why does a change in concentration of reactants or products not affect the equilibrium constant at a certain temperature?

Nathan Mariano 2G

Does the s orbital have any degeneracies? The internet says that it does not, but I have heard that it has a degeneracy as one. Degeneracy is defined as orbitals with the same energy. However, the s orbital does not have another orbital with the same energy.

Nathan Mariano 2G

How do we tell the difference if a coordination compound is square planar or tetrahedral? Does the molecular shape of tetrahedral change the number of bonding sites compared to square planar?

Nathan Mariano 2G

If the total charge of a coordination complex is negative, then do we have to add a negative charge outside of the brackets?

Nathan Mariano 2G

How do you determine which compound has the higher boiling point if they both have similar intermolecular forces? For example, H2S and H2Se.

Nathan Mariano 2G

How do you determine which structure is the most stable? For example, why does the resonance structure of SO4^2- prefer to form a two double bond with two oxygen instead of forming a double bond with one sulfur and one oxygen? Sulfur and Oxygen both have the same amount of valence electrons.

Nathan Mariano 2G

Is there a reason why sigma bonds are stronger than pi bonds?

Nathan Mariano 2G

Why does only one sigma bond form between two atoms? Why can multiple pi bonds form between two atoms?

Nathan Mariano 2G

Hybridization is defined as the combination of atomic orbitals to form new hybrid orbital that explain the structure of the molecules in the VSEPR model. The number of hybrid orbitals is dependent on the number of regions of electron densities around the atoms.

Nathan Mariano 2G

Degeneracy is defined as having two or more quantum states in a quantized energy level. For example, the p orbital has three degeneracies because it has three quantum states (or three orbitals of the same energy). The d orbital has five degeneracies because it has five quantum states (or five orbita...

Nathan Mariano 2G

We balance chemical equations due to the law of conservation of mass, which states that mass can neither be created or destroyed. Therefore, in a chemical reaction, the total mass of the reactants must be equal to the total mass of the products. Balancing equations accounts for the total mass of the...

Nathan Mariano 2G

When drawing the Lewis structure of a compound, how do we determine the vectors for each atom? From the vectors, how do we deduce that a molecule is polar or nonpolar?

Nathan Mariano 2G

When there are three electron densities around the central atom, the electron arrangement is trigonal planar. Since there are no lone pairs, the molecular shape is also trigonal planar. When there are four electron densities around the central atom, the electron arrangement is tetrahedral. However, ...

Nathan Mariano 2G

According to the information we learned in lecture, double bonds consist of one sigma bond and one pi bond and that triple bonds consist of one sigma bond and two pi bonds. Why can't double bonds and triple bonds consist of solely sigma bonds or solely pi bonds?

Nathan Mariano 2G

How does the presence of lone pairs in an atom affect the deflection angle of an atom?

Nathan Mariano 2G

Why is the 3d orbital placed before the 4s orbital? When viewing ptable.com (Dynamic Periodic Table), the 3d orbital is placed after the 4s orbital.

Nathan Mariano 2G

How do hydrogen bonds affect the boiling and melting point of a substance? What accounts for the difference in the boiling and melting point in H2O and H2S? I was confused about the difference in the boiling and melting point of the H2O and H2S during lecture because they both have the same amount o...

Nathan Mariano 2G

What is the isoelectronicity? How do we find if one element is isoelectronic to another element?

Nathan Mariano 2G

What is the difference between atomic radius and ionic radius?

Nathan Mariano 2G

Arrange S^-2, Cl-1, P-3 in order of increasing ionic radius. The correct order according to the textbook of increasing ionic radius is Cl^1-,S^2-,P^3-. Why is it in that order? My thought process is the same as atomic radius: as you add valence electrons, the ionic radius decreases. Using that proce...

Nathan Mariano 2G

In the particle in a box model, a particle is confined by barriers. These barriers cannot be penetrated by the particle. The particle is free to move at any speed and it can be in any position within the barriers of the box. At certain positions known as spatial nodes, the particle may not be detect...

Nathan Mariano 2G

Why are hydrogen bonds weaker than ionic and covalent bonds?

Nathan Mariano 2G

What is the effective nuclear charge? How does it affect electrons?

Nathan Mariano 2G

Can someone please explain how the DeBroglie Equation can be applied to classical objects (such as a baseball or a table)? Do classical objects have a wavelength?

Nathan Mariano 2G

RoopshaChatterjee 1G wrote:With all the equations in this section how do we know when a v is frequency and when it represents velocity?

In response to your question, there are different notations for frequency and velocity. Frequency is denoted with the Greek letter nu, while velocity is denoted with the letter v.

Nathan Mariano 2G

Radial nodes are spherical regions, while angular nodes are flat planes (or cones). The probability of finding an electron in both of these regions is zero. Radial nodes have fixed radii, while angular nodes have fixed angles. For radial nodes, the principal quantum number determines the number in a...

Nathan Mariano 2G

Why are electron energy levels quantized? Why can't electrons exist in between quantized electron energy levels?

Nathan Mariano 2G

Why do different metals have different threshold energies?

Nathan Mariano 2G

Threshold energy is the amount of energy required to remove a single electron from a metal surface. Different metals have different threshold energies due to the difference in electronegativity. Each photon must have enough energy to remove an electron regardless of the amount of photons present in ...

Nathan Mariano 2G

The use of Avogadro's number is only necessary when the problem is asking for the atoms of a molecule or formula units of a compound. In this case, the question is asking you to find the moles of each unit; therefore, it is unnecessary to multiply by Avogadro's number. Simply, convert the mass of th...

Nathan Mariano 2G

The prefix "milli-" denotes multiplication by 10^-3. One millimole is equivalent to 10^-3 moles.

Nathan Mariano 2G

The hectometer is an SI unit, however it is rarely used.

Nathan Mariano 2G

The Student Solutions Manuals shows that the answer (1.73 x 10^26 picometers) must be converted to meters and then kilometers. However, the Student Solutions Manual does not state why. Will we lose points on the test if we convert an answer to the wrong units?

Nathan Mariano 2G

In exercise E.1, I multiplied 6.022 x !0^23 to 288 picometer and received a final answer of 1.73 x 10^26 picometers. Is it necessary to change the final answer from picometers to meters or kilometers? If so, why?

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