CHEMISTRY COMMUNITY

haley f

(a) Use a graphing calculator or standard graphing software to make an Arrhenius plot of the data shown here for the conversion of cyclopropane into propene and calculate the activation energy for the reaction. (b) What is the value of the rate constant at 600 °C? How are we supposed to find the act...

haley f

A certain reaction has an activation energy of 43.60 kJ/mol. At what Kelvin temperature will the reaction proceed 3.00 times faster than it did at 345 K?

If we don't know k1 and k2, how can we solve this problem?

haley f

The presence of a catalyst provides a reaction pathway in which the activation energy of a reaction is reduced by 67.00 kJ⋅mol−1 . Uncatalyzed: A⟶B Ea=133.00 kJ⋅mol−1 Catalyzed: A⟶B Ea=66.00 kJ⋅mol−1 Determine the factor by which the catalyzed reaction is faster than the uncatalyzed reaction at 289....

haley f

A certain reaction has an enthalpy of ΔH=59 kJ and an activation energy of Ea=91 kJ.
What is the activation energy of the reverse reaction?

I know that to get the Ea we need to do Etransition - E reactants, but how do you find these values?

haley f

For the reversible, one‑step reaction, A+A⥫⥬ B+C the rate constant for the forward reaction, k1 , is 289 L⋅mol−1⋅min−1 and the rate constant for the reverse reaction, k1 , is 357 L⋅mol−1⋅min−1 at a given temperature. The activation energy for the forward reaction is 44.2 kJ⋅mol−1 , whereas the activ...

haley f

Evaluate the unknown quantity in each of the following cells:(a) Pt(s)|H2(g, 1.0 bar)|H+(pH = ?)||Cl−(aq, 1.0 mol⋅L−1)|Hg2Cl2(s)|Hg(l), Ecell = +0.33 V.(b) C(gr)|Cl2(g, 1.0 bar)|Cl−(aq, ?)||MnO4−(aq, 0.010 mol⋅L−1),H+(pH = 4.0),Mn2+(aq, 0.10 mol⋅L−1)|Pt(s), Ecell = −0.30 V. For part a I keep getting...

haley f

For the first-order reaction A → 3 B + C, when =[A]0=0.015 mol⋅L−1, the concentration of B increases to 0.018 mol⋅L−1 in 3.0 min. (a) What is the rate constant for the reaction expressed as the rate of loss of A? (b) How much more time would be needed for the concentration of B to increase to 0.30 m...

haley f

7B.7 Substance A decomposes in a first-order reaction and its half life is 355 s. How much time must elapse for the concentration of A to decrease to (a) one-eighth of its initial concentration; (b) one-fourth of its initial concentration; (c) 15% of its initial concentration; (d) one-ninth of its i...

haley f

Dinitrogen pentoxide, N2O5, decomposes by first-order kinetics with a rate constant of 3.7×10−5 s−1 at 298 K. (a) What is the half-life (in hours) of N2O5 at 298 K? (b) If [N2O5]0=0.0567 mol⋅L−1, what will be the concentration of N2O5 after 3.5 h? (c) How much time (in minutes) will elapse before th...

haley f

Determine the rate constant for each of the following first-order reactions, in each case expressed for the rate of loss of A: (a) A → B, given that the concentration of A decreases to one-half its initial value in 1000. s; (b) A → B, given that the concentration of A decreases from 0.67 mol⋅L−1 to ...

haley f

Hi, I understand how to balance a redox reaction under basic conditions, but I can rarely seem to get the problems right. I know I have to separate into half reactions, balance everything but O and H, then balance H with H2O, then H with H+ and add the same number of OH- as H+ to both sides, and the...

haley f

For the half reaction: H2O2 —> O2 , can you just add H^+ and 2 electrons to balance the equation? Sorry I know that maybe a simple question but I keep getting a mistake and I’m not sure if this may be my problem I don't think you can do this because then it is in acidic solution and the question as...

haley f

Identify the oxidizing and reducing agents in the skeletal (unbalanced) reaction. Then, balance the reaction, including the phase (solid, liquid, etc.) of each species. The reaction takes place in basic aqueous solution. [Pb(OH)4]2−(aq)+ClO−(aq)⟶PbO2(s)+Cl−(aq) my balanced equation : [Pb(OH)4]2−(aq)...

haley f

Identify the oxidizing and reducing agents in the skeletal (unbalanced) reaction. Then, balance the reaction, including the phase (solid, liquid, etc.) of each species. The reaction takes place in basic aqueous solution. Cl2O7(g)+H2O2(aq)⟶ClO−2(aq)+O2(g) my balanced equation : Cl2O7(g)+5H2O2(aq)⟶ClO...

haley f

For a particular redox reaction, BrO− is oxidized to BrO−3 and Ag+ is reduced to Ag . Complete and balance the equation for this reaction in basic solution. The phases are optional. balanced reaction: Mine: BrO−+2Ag+⟶BrO−3+2Ag+2H2O Hi, I'm getting really stuck on the basic solution part of this prob...

haley f

What would the potential of a standard hydrogen electrode (S.H.E.) be under the given conditions?

[H+]=0.67 M PH2=3.3 atm T=298 K

How would I begin this problem, would I use the Nernst equation?

haley f

Calculate the cell potential for the reaction as written at 25.00 °C , given that [Cr2+]=0.768 M and [Sn2+]=0.0150 M . Use the standard reduction potentials in this table. Cr(s)+Sn2+(aq)↽−−⇀ Cr2+(aq)+Sn(s) Hi, to do this problem I would use the nernst equation, and for Enaught I got .77, 2 for n, an...

haley f

Yes, we have only been using K to refer to the equilibrium constant so far!

haley f

In lecture he went through how he got the Van't Hoff equation in this form by subtracting the equation with one temperature from the equation with another. Since the ΔS° term was a constant, it cancels out when we complete the subtraction.

haley f

Because this equation relates the change in temperature to the change in reaction constant, you can use it to figure out either one of these things, depending on the information given.

haley f

ΔH naught is the change in enthalpy under standard conditions and ΔH is just the change in enthalpy!

haley f

They're the same equation, one just has the negative sign pulled out to the front, which is why the T1 and T2 are switched!

haley f

Thermal equilibrium means that the temperature inside and outside the system are the same. This also means that the net change in temperature is 0, so if heat leaves the system for the surroundings, heat must also enter the system from the surroundings to maintain the same temperature.

haley f

For a gaseous reaction, standard conditions are 298 K and a partial pressure of 1 bar for all species. For the reaction N2(g)+3H2(g)↽−−⇀2NH3(g) the standard change in Gibbs free energy is ΔG∘=−32.8 kJ/mol. What is ΔG for this reaction at 298 K when the partial pressures are PN2=0.100 bar, PH2=0.200 ...

haley f

Three liquid samples of known masses are heated to their boiling points with the use of a heater rated at 400.0 W . Once the boiling points of each sample are reached, the samples are heated for an additional 5.94 min , which results in the vaporization of some of each sample. After 5.94 min , the s...

haley f

A particular container holds 3.86 mol of neon gas. The volume of this container can be altered by sliding a piston in or out. The volume is changed from 8.30 L to 6.90 L while at the same time the temperature is changed from 322 K to 289 K. The molar heat capacity, CV,m, for neon is 12.47 J/(mol · K...

haley f

Consider a process in which an ideal gas is compressed to one-half of its original volume at constant temperature. Calculate the entropy change per mole of gas. I know I have to use deltaS = nRln(V2/V1), n would be 1 and I don't have the volumes but V2 is double V1 so would I just use 2? Also the an...

haley f

A 0.357 mol sample of SO2(g), initially at 298 K and 1.00 atm, is held at constant pressure while enough heat is applied to raise the temperature of the gas by 17.9 K. Calculate the amount of heat q required to bring about this temperature change, and find the corresponding total change in the inter...

haley f

Automobile airbags contain solid sodium azide, NaN3, that reacts to produce nitrogen gas when heated, thus inflating the bag. 2NaN3(s)⟶2Na(s)+3N2(g) Calculate the value of work, w, for the system if 36.2 g NaN3 reacts completely at 1.00 atm and 22 ∘ C. If you don't know the change in volume, what eq...

haley f

A sample of an ideal gas in a cylinder of volume 2.84 L at 298 K and 2.69 atm expands to 8.96 L by two different pathways. Path A is an isothermal, reversible expansion. Path B has two steps. In the first step, the gas is cooled at constant volume to 1.38 atm . In the second step, the gas is heated ...

haley f

At constant volume, the heat of combustion of a particular compound, compound A, is −3417.0 kJ/mol. When 1.563 g of compound A (molar mass =104.57 g/mol) is burned in a bomb calorimeter, the temperature of the calorimeter (including its contents) rose by 5.629 ∘C. What is the heat capacity (calorime...

haley f

An ice cube with a mass of 49.4 g at 0.0 ∘C is added to a glass containing 442 g of water at 45.0 ∘C . Determine the final temperature of the system at equilibrium. The specific heat capacity of water, Cs , is 4.184 J/g⋅∘C , and the standard enthalpy of fusion, ΔH∘fus , of water is 6.01×103 J/mol . ...

haley f

Yes, in this situation K will be increased because the system is endothermic, but the K value will not always increase with a temperature increase, it really depends on if the system is endothermic or exothermic.

haley f

You are correct! When pressure increases the reaction will favor the side with fewer moles of gas because solids and liquids won't change their volume when pressure is increased or decreased because it is very hard to do so.

haley f

If the pressure of a system increases, the system will want to try to decrease the pressure in order to reach equilibrium. To do this, the system will favor the side of the reaction with fewer moles of gas.

haley f

When applying Le Chatelier's principle, you only need to take into consideration the gasses!

haley f

Yes! You are correct, when using Le Chatlier's principle you would not need to take the solids and liquids into consideration because they are not measured in concentration. Also, the only thing that can change K is temperature.

haley f

If you take the -log of the concentration of the acid [H+], then it will yield pH. If you take the -log of the concentration of the base [OH-] then it will yield the pOH of the solution.

haley f

I believe you are correct. The only thing that can change the equilibrium constant is temperature. If the concentration of the products increase, then the reaction will go towards the reactants and make more reactants so it is at equilibrium. Therefore, the ratio of products/reactants will still be ...

haley f

For the midterm, how often will we be using this? Will it just be required to solve certain problems or will there be specific questions about the equation?

haley f

It's my understanding that we just have to know what he covered in lecture, which was basically how pressure/volume, temperature, and concentration changes affect the equilibrium of the reaction!

haley f

You would only need to consider the gases! He mentioned in class that we can't really give enough pressure to change the volume of solids and liquids in this course so we don't consider it!

haley f

The Ka of a monoprotic weak acid is 0.00787. What is the percent ionization of a 0.156 M solution of this acid? When I did this problem Sapling said my assumption wasn't correct, which I can just do the quadratic so it's okay, but is there any way to know before doing the problem that x is too big t...

haley f

A monoprotic weak acid, HA , is ionized according to the reaction

HA(aq)+H2O(l)↽−−⇀A−(aq)+H3O+(aq). pKa=4.49

where A− is the conjugate base to HA.
For this weak monoprotic acid, the predominant species present at pH 1.64 is:
neutral, charged, unknown

How would I start this problem?

haley f

Classify these salts as acidic, basic, or neutral.
NaCN, KCl, NH4CLlO4, K2CO3, LiClO4

I know that you have to determine if these salts came from a weak or strong acid or base but I keep getting confused of what means what. If a salt is the conjugate acid of a weak base, is the solution acidic?

haley f

The reaction N2O4↽−−⇀2NO2 is allowed to reach equilibrium in a chloroform solution at 25 ∘C . The equilibrium concentrations are 0.437 mol/L N2O4 and 2.21 mol/L NO2 . Kc = 11.2 Calculate the equilibrium concentrations of N2O4 and NO2 after the extra 1.00 mol NO2 is added to 1.00 L of solution. After...

haley f

Yes, if you have K p = 343, you can find the total final pressure by setting up an ICE table. In your equation K p = [PCl 5 ] / ('[PCl 3 ][Cl 2 ]), your PCl 5 term would be (0.062 - x), and PCl 3 and Cl 2 would both be +x. You'd then have to do some rearranging to get a quadratic equation 343x 2 + ...

haley f

Consider the reaction at 500°C . N2(g)+3H2(g)<->2NH3(g). Kc=0.061 If analysis shows that the composition of the reaction mixture at 500°C is 0.903 mol⋅ L−1N2 , 4.37 mol⋅ L−1H2 , and 3.88 mol⋅ L−1NH3 , what is the value of the reaction quotient Q? In this question, how do we take the temperature into...

haley f

N2O4<->2NO2
Determine how the addition of extra NO2 in the previous step will affect the rate constant, Kc .

I know that when more NO2 is added, more N2O4 will be created because it is trying to reach equilibrium, but this question confused me. Is the answer that K doesn't change?

haley f

Consider this system at equilibrium. A(aq)<->B(aq) ΔH++250 kJ/mol What can be said about Q and K immediately after an increase in temperature? How will the system respond to the change in temperature? Does anyone have any ways to remember the effects on temperature on the system and when Q> or < K?

haley f

At a certain temperature, the given reaction has an equilibrium constant of Kp=343 . PCl3(g)+Cl2(g)<->PCl5(g) PCl5 is placed in a sealed container at an initial pressure of 0.0620 bar. What is the total pressure at equilibrium? What is the equation used for pressure? Would it be PCl5/ (PCl3 x PCl2)?

haley f

At a certain temperature, 0.780 mol SO3 is placed in a 2.50 L container. 2SO3(g)<->2SO2(g)+O2(g) At equilibrium, 0.110 mol O2 is present. Calculate Kc. I know how to figure out the concentration of SO3 and O2 using the moles and volume, but how do you figure out the concentration of SO2?

haley f

I was actually wondering the same thing because if the bonds are tighter they hold the H more closely, so it doesn't make sense that it is the opposite.

haley f

Rylee Mangan 2B wrote:When pH > pKa then the acid will be negatively charged.
When pH < pKa then the acid will be neutral.

That makes sense, thank you!

haley f

A monoprotic weak acid, HA , is ionized according to the reaction HA(aq)+H2O(l)↽−−⇀A−(aq)+H3O+(aq)pKa=4.08 where A− is the conjugate base to HA. For this weak monoprotic acid, the predominant species present at pH 2.32 is: unknonw, charged, or neutral I know that when pH is less than pKa HA will bec...

haley f

Arrange the oxoacids of chlorine according to strength. HClO4, HClO3, HClO2, HClO
How do you know which of these has the strongest bond to oxygen?

haley f

Assuming equal concentrations, arrange these solutions by pH. HNO3(aq)
How do you know the pH of a solution like this?

haley f

Classify these salts as acidic, basic, or neutral. K2CO3, Na2S, NH4ClO4, KCl, LiBr
Hi guys, how would you go about this problem? I kinda know that it depends on if the anion is the conjugate of a strong or weak acid, but I'm stuck on how to do this.

haley f

Andrew Jubintoro 3A wrote:It's how the 4 sp³ are arranged.
The relative orientations would be the same as the original electron arrangement you used to determine the hybridization.
Screen Shot 2020-12-08 at 01.50.15.png

Ohh so it's referring to the shape it would create right?

haley f

Write the chemical equations of the two proton transfer equilibria that demonstrate the amphiprotic character of (a) HCO3−; (b) HPO42−. Identify the conjugate acid–base pairs in each case.

In this question protons refer to the H+ right?

haley f

State the relative orientations of each of the following hybrid orbitals: (a) sp3
For this question, what does it mean by relative orientations? Is it like an sp3 hybridization is the combination of one s orbital and three p orbitals?

haley f

To determine the coordination number of a coordinate compound you count the bonds connected to the central atom. For example the coordination number in [Fe(CN)6] is 6 as there are 6 ligands connected to the central transition metal atom. I hope this helps! Thank you, this makes a lot of sense! For ...

haley f

I'm having some trouble with this Sapling problem. I know that Cl2 has a charge of 2- so the coordination compound must have a charge of 2+, so would the charge of Co be 3+?
Give the oxidation state of the metal species in the complex [Co(NH3)5Cl]Cl2

haley f

Is the geometry for a coordination compound based on the number of atoms attached to the metal? And is it any of the options for that number of regions of electron density? Like either tetrahedral or square planar - how could you distinguish?

haley f

How do you figure out the coordination number of a coordination compound?

haley f

What does the coordination number refer to? Is it the charge on the coordination compound?

haley f

Daniela_Martinez_3B wrote:Yes, you're correct for part a! For part b, it's invalid because l=0 so ml must also equal 0. Part c is also invalid because the maximum value l can have is n-1 and n=4 so lmax=3.

Thank you! How do you get ml from l? Like why does l=0 restrict the value of ml?

haley f

Jillian Labador 2F wrote:Hi! I believe the electron configuration for Manganese (Mn) is [Ar] 3d^5 4s^2 so an electron would be removed from the 4s orbital to form Mn+

This is very helpful, but why is it 3d^5 instead of 3d^10?

haley f

For each of the following ground-state atoms, predict the type of orbital (1s, 2p, 3d, 4f, etc.) from which an electron will be removed to form the +1 ion: (a) Ge; (b) Mn; (c) Ba; (d) Au.

For part b, why is the 4s removed and not the 4p? Is my electron configuration wrong? [Ar]4s^2 4p^5

haley f

Write the ground-state electron configuration for each of the following atoms: (a) sodium; (b) silicon; (c) chlorine; (d) rubidium.

I understand how to do this, but how come 5s^1 comes before 4d^1 and how do we know when to do this?

haley f

Of the following sets of four quantum numbers {n, l, ml, ms}, identify the ones that are forbidden for an electron in an atom and explain why they are invalid: (a) {4,2,−1,+1/2}; (b) {5,0,−1,+1/2}; (c) {4,4,−1,+1/2}. For part a it would be 4d where ml could be -2, -1, 0, 1, or 2, and -1 is given so ...

haley f

Karla_Coronado_1J wrote:Determine whether each of the following electron configurations represents the ground state or an excited state of the atom given.

I do not know how to go about this. May someone explain how to answer this question?

Thank you!

How is Pauli's exclusion principle seen on in these pictures?

haley f

How many orbitals can have the following quantum numbers in an atom: (a) n=2, l=1; (b) n=4, l=2, ml=−2; (c) n=2; (d) n=3, l=2, ml=+1? I know how to do part a, but I am confused on how the ml affects the number of orbitals, can someone please explain? Also for part c, how do we find the number of orb...

haley f

For each orbital listed (a) 6p; (b) 3d; (c) 2p; (d) 5f, give the possible values of the magnetic quantum number.

Do we just have to memorize what magnetic quantum numbers go with each orbital or is there a way to figure it out?

haley f

As an example of 3d this is another way of writing (n)(l) since n = 3 and l = 2 = d for all angular momentum quantum numbers we have l=0; s l=1; p l=2; d l=3; f l=4; g for the first question (a) 6p; (b) 3d; (c) 2p; (d) 5f (a) n =6 and l = 1 (b) n = 3 and l = 2 (c) n = 2 and l = 1 (d) n = 5 and l = ...

haley f

) How many values of the quantum number l are possible when n=7? (b) How many values of ml are allowed for an electron in a 6d-subshell? (c) How many values of ml are allowed for an electron in a 3p-subshell? (d) How many subshells are there in the shell with n=4? I am confused on part b. I know l i...

haley f

The question states" How many orbitals are in sub-shells will l equal to a)0 b)2 c)1 d)3" for a) you know that L=0 corresponds to a s-orbital and s orbitals have 1orbital therefore the answer is 1 orbital b) l=2 corresponds to a d-orbital and d orbitals have 5 orbitals , therefore the ans...

haley f

The sum of oxidation numbers for each element must add up to the overall charge of the molecule (so in this case, it should equal -1). Oxygen has an oxidation of -2, and since there are four oxygen atoms, the sum of oxidation states for oxygen is -8. Now, you can pick an oxidation state for the chl...

haley f

Which molecules exhibit only London (dispersion) forces? CH3F BCl3 Br2 NH3 CH4 Where do I begin with this question? I'm confused on what London (dispersion) forces are? I think they may have been called something else in lecture. I know Br2 is one of them because it doesn't have any dipole moment.

haley f

Acetone can form hydrogen bonds with water. Select which image represents an acetone molecule interacting with a water molecule.

The hint says there must be an O on either side of the H in the H-bond, why is this?

haley f

What is the oxidation number of chlorine in the perchlorate ion? (ClO4-)

How do I figure the oxidation number out?

haley f

How many electrons in an atom could have these sets of quantum numbers?
n=2
n=4,l=1
n=7,l=3,ml=−1

I am lost on where to start on this question, can someone please help me out?

haley f

A baseball must weigh between 5.00 and 5.25 ounces (1 ounce = 28.3g). What is the wavelength of a 5.15-ounce baseball thrown at 92 mph? I found the answer but it is a little off in the scientific notation. I converted oz to grams and 92 mph to 41.1277 m/s. I did wavelength = h/145.745g*41.1277 m/s. ...

haley f

[quote="haley f"]The velocity of an electron that is emitted from a metallic surface by a photon is 3.6×10^3 km⋅s−1. (a) What is the wavelength of the ejected electron? (b) No electrons are emitted from the surface of the metal until the frequency of the radiation reaches 2.50×10^16Hz. How...

haley f

The velocity of an electron that is emitted from a metallic surface by a photon is 3.6×10^3 km⋅s−1. (a) What is the wavelength of the ejected electron? (b) No electrons are emitted from the surface of the metal until the frequency of the radiation reaches 2.50×10^16Hz. How much energy is required to...

haley f

Alright finding the molarity is the first step. For the Na2CO3 molarity is 0.08 M. You might want to convert the values from mmol to mols. but 1 mmol= .001 mol. To find a) you convert the mmol to mol to get 0.002015 mole Na. Since theres 2 Na's in Na2CO3 the molarity is gonna be twice so instead of...

haley f

Leyla Anwar 1C wrote:Hi, where does the 32.05 come from? Is that how to make any metal a sulfide? Or is that specific to Ca?

I was wondering the same thing! Here's what I found: Calcium sulfide is Ca and S so the 32.05 is simply the molar mass of sulfur!

haley f

Hi! I actually kept messing this part up too. This is how I ended up finding the mass of a single Helium atom. The tricky part of dimensional analysis is the units and cancelling them out accordingly. To solve for the uncertainty in the helium atom's velocity, we plug that into the equation h/(4pi)...

haley f

What is the minimum uncertainty in a helium atom's velocity if the position is known within 1 angstrom? I figured out the correct answer for the first part of the problem asking about the electron but I am stuck on the second part. I think I am having a hard time with the conversions of the mass of ...

haley f

The mass of a single fluorine molecule is what is listed on the periodic table of elements. Since it is diatomic, you should double the amu. To get the correct wavelength, you have to convert the g/molecule into kg/molecule. Then using, wavelenth=h/(mv), the kg in the m will cancel with the kg in p...

haley f

Hi. Can someone help me solve this problem? I'm not sure what I should solve for first if I'm just given the work function. As you may well know, placing metal objects inside a microwave oven can generate sparks. Two of your friends are arguing over the cause of the sparking, with one stating that ...

haley f

The maximum wavelength of the radiation that will eject electrons occurs when the energy of the incident light equals the work function. When you are given the work function, you can calculate the wavelength of the radiation. work function = E(photon) = hc/(wavelength) Does this mean that whenever ...

haley f

Will we only need to know this equation for a hydrogen atom? The En=-(hR)/n^2 equation. And from this equation how do we determine how many spectral lines there will be?

haley f

Prof Lavelle said this was unexpected, so does that mean that electrons don't always have wavelike properties?

haley f

Is delta E always equal to the Energy of the photon like in the example from Friday's lecture?

haley f

Divide the total energy by the work function to see how many electrons the energy can displace. 6.78×10−7 J/4.28494×10−19 J/photon Important concepts: One photon with enough energy to displace an electron will only displace one electron. In other words, there is a one-photon to one electron ratio i...

haley f

So for this question would we use the equation E(photon) - E(energy to remove e-) = E(excess)? And in this case E(energy to remove e-) is the work function that the question is asking for? And do you set the equation (E(photon) - E(energy to remove e-)) equal to the maximum kinetic energy? Here's th...

haley f

Does quantized just mean focusing on the individual molecules or photons rather than the continuous flow of water or light?

haley f

Who are the Step up Sessions taught by? And are they helpful?

haley f

When taking the molar masses off the periodic table, how many decimal points do we need to use? Is it generally okay to use 1 for Hydrogen and 12 for Carbon?

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