CHEMISTRY COMMUNITY

Fionna Shue 4L

Standard Gibbs free energy is an extensive property because in the equation ∆G=-nFE, you have to multiply E by the number of electrons that are transferred.

Fionna Shue 4L

K = 1 means that the products and reactants are at equal concentrations at equilibrium. Because this is not always the case, K does not always equal 1 at equilibrium.

Fionna Shue 4L

Can 2A -> B + C be a first order reaction and why?

Fionna Shue 4L

Use the data in Appendix 2B and the fact that, for the half- reaction F2(g) 2 H (aq) 2 e S 2 HF(aq), E 3.03 V, to calculate the value of Ka for HF.

How do you know the other half reaction for this cell?

Fionna Shue 4L

14.55 A 1.0 m NiSO4(aq) solution was electrolyzed by using inert electrodes. Write (a) the cathode reaction; (b) the anode reaction. (c) With no overpotential or passivity at the electrodes, what is the minimum potential that must be supplied to the cell for the onset of electrolysis? For the anode ...

Fionna Shue 4L

Conceptually, why does the half life of a first order reaction not depend on the initial concentration?

Fionna Shue 4L

Average rate is the change in the value of a quantity divided by the elapsed time. The instantaneous rate on the other and is the rate of a change at an exact moment in time.

Fionna Shue 4L

Is the rate law for the rate determining step always equal to the overall rate law?

Fionna Shue 4L

For Worksheet 7 #8d, why is OH-(aq) not included in the cell diagram?

Fionna Shue 4L

Are we supposed to include H+ and OH- ions when we are drawing the cell diagram?

Fionna Shue 4L

Why is standard Gibbs free energy for the vaporization of water at 100 degrees Celsius 0?

Fionna Shue 4L

For the final answer, you would use the least number of sig figs that is reported in the question. For your example, I would plug in all 6 sig figs for that specific calculation, but my final answer would only have 3 sig figs.
I don't think that you have to use all 6 sig figs, this is just what I do.

Fionna Shue 4L

If there is no change in volume, that means that the system has not expanded or been compressed. If there is no expansion or compression, there is no work because the work that we are referring to is only expansion/compression work.

Fionna Shue 4L

Yes, this would be an irreversible system

Fionna Shue 4L

If the reaction is taking place in an open beaker, pressure will be constant

Fionna Shue 4L

Entropy is a state function so the path that it takes from the initial to final state does not matter- only the initial and final states themselves. Therefore, it does not matter if the path was reversible or irreversible. If the initial and final states match, then the change in entropy will be the...

Fionna Shue 4L

Will we have to know strong acids and bases for the midterm?

Fionna Shue 4L

Because there is 197 grams of Carbon, 197g/12.01g.mol^-1 = 16.4 moles of Carbon. 16.4 moles of carbon / 4 moles needed and multiply that by the standard enthalpy = (16.4 moles/4 moles)* 358.8 kJ = 1.47*10^3 kJ

Fionna Shue 4L

An ideal gas in a cylinder was placed in a heater and gained 5.50 kJ of energy as heat. If the cylinder increased in volume from 345 mL to 1846 mL against an atmospheric pressure of 750. Torr during this process, what is the change in internal energy of the gas in the cylinder? I found that the w = ...

Fionna Shue 4L

Coolant un a refrigerator coil is actually a closed system, not an isolated system.

Fionna Shue 4L

Which would you expect to be larger for a given substance, CV,m or CP,m and why?

Fionna Shue 4L

During a combustion reaction, a compound reacts with O2 and burns. The two reactants are H2 and O2. Because there is no Carbon in the reactants, CO2 would not form. Instead, the equation would be 2H2 + O2 --> 2H2O

Fionna Shue 4L

When you are burned by water vapor, the vapor has to go through a phase transition to turn from vapor to liquid. The vapor releases energy as it cools down to the liquid state. When you are burned by boiling water, it does not change phases. Because the water vapor has has a phase transition, it wil...

Fionna Shue 4L

If a piston is compressing, then work is being done to the system and the value of work would be positive.

Fionna Shue 4L

Given Ka, you can find the H+ concentration and the pH value. pOH = 14- pH and the concentration of OH- is 10^(-pOH).

Another way of finding the concentration of OH- is knowing that [OH-]*[H+]=10^-14. Once you have the concentration of H+, [OH-]=(10^-14)/[H+]

Fionna Shue 4L

Will we have to memorize strong acids and bases for Test 1?

Fionna Shue 4L

The graph gives you the initial and equilibrium partial pressures. A's partial pressure decreases by 10, B's partial pressure increases by 5, and C's partial pressure increases by 10. That means the molar ratio for A:B:C is 2:1:2 and the balanced equation is 2A ⇌ B + 2C

Fionna Shue 4L

Calculate the pH, pOH, and percentage protonation of solute in each of the following aqueous solutions: (a) 0.057 m NH3(aq); (b) 0.162 m NH2OH(aq); (c) 0.35 m (CH3)3N(aq); (d) 0.0073 m codeine, given that the pKa of its conjugate acid is 8.21. For parts b, c, and d, how are we supposed to determine ...

Fionna Shue 4L

For this question you would have to set up and ICE table. The initial composition for NO is given (1.0 bar), and the initial compositions for N2 and O2 would be 0 because the reaction hasn't taken place yet. X is the equilibrium concentration of N2 so the change in N2 would be +x. N2 and O2 have a 1...

Fionna Shue 4L

Yes, the flasks are shown in chronological order.

Fionna Shue 4L

For the reaction 2AgNO3(aq) + 2NaOH(aq) ⇌ Ag2O(s) + 2NaNO3(aq) + H2O(l), why is the equilibrium constant K = 1/[Ag+]^2[OH-]^2? What are spectator ions and why do they cancel?

Fionna Shue 4L

A represents the central atom, X is the number of atoms bonded to the central atom, and E is the number of lone pairs on the central atom.

Fionna Shue 4L

For worksheet 9 #2, why is the answer BF3? How can Cl- act as a lewis base?

Fionna Shue 4L

What's the difference between cyano and cyanido? For example in Potassium tetracyanonickelate(II), why is it cyano and not cyanido?

Fionna Shue 4L

If there is a central atom that the three atoms and the one lone pair is attached to, then the VSEPR formula would be AX3E. A is the central atom, X3 represents three atoms attached to the central atom, and E represents the one lone pair attached to the central atom.

Fionna Shue 4L

If the lewis structure is symmetrical, then it is non-polar because the dipole moments cancel out. If the lewis structure is asymmetrical or there are lone pairs on the central atom, then it is polar

Fionna Shue 4L

sp means that there are two regions of electron density. If there are three regions of electron density rather than two, then there would be another p, making it sp2

Fionna Shue 4L

In an sp3 orbital, it is 25% s-character and 75% p-character. In an sp2 orbital, it is 33% s-character and 67% p-character. Bond angle increases from sp3 to sp2 so bond angle increases as as the s-character of a hybrid orbital increases.

Fionna Shue 4L

The central atom, C, has four regions of electron density- two bonding pairs and two lone pairs. This makes a bent shape- similar to the H2O example that Dr. Lavelle went over in class.

Fionna Shue 4L

The bond angle should be <109.5, but since it's only a little less than 109.5, it's still around 109.5

Fionna Shue 4L

In addition, the CF4 bond is the shortest because the size of an F is the smallest compared to Cl and Br. The smaller the size of the atoms, the shorter the bonds.

Fionna Shue 4L

Why is AX2E3 linear but AX2E2 bent?

Fionna Shue 4L

For H2O, why are the two lone pairs next to each other? If lone pair- lone pair repulsion is the strongest, why aren't the two lone pairs on opposites sides of each other?

Fionna Shue 4L

Can we bring a scientific calculator for the midterm?

Fionna Shue 4L

The velocity is 5.00 +/- 5 so it would range from 0 (5-5) to 10 (5+5). The uncertainty in velocity would be 10-0=10.

Fionna Shue 4L

Both protons and neutrons have mass, so you would use the de Broglie equation. The mass of a proton is 1.6726*10^-27 kg and the mass of a neutron is 1.6749*10^-27 kg

Fionna Shue 4L

How do I find the energy of an electron if I'm only given its wavelength? Can I use the equation E=hv or does that only apply to particles without mass?

Fionna Shue 4L

The dots can go on any four sides, but keep in mind that two dots next to each other means that those two electrons are paired. If the 4 electrons that you're drawing aren't paired, the structure would have one dot on each of the 4 sides.

Fionna Shue 4L

The 3d orbital has higher energy than the 4s orbital when the 4s orbital is not filled.

Fionna Shue 4L

No, the speed of light is the ultimate speed limit of the universe

Fionna Shue 4L

To solve for this, we would use the equation ∆x∆p = h/4π. For an electron, ∆p = m∆v, and therefore, m∆x∆v = h/4π. The uncertainty on position of an electron would be the diameter of the atom so ∆x = 350 pm. "m" is the mass of the electron which is 9.109*10^-31 kg and h=6.626*10^-34 J.s

Fionna Shue 4L

In addition, I think Dr. Lavelle mentioned that anything less than 10^-18 m is not detectable.

Fionna Shue 4L

Do percentages count as sig figs? For example, if we were to find 25% of 10.6, would the answer have 3 sig figs or 2?

Fionna Shue 4L

For part b, it is asking for the amount in moles of SO3 molecules, so the answer would be in moles. Moles can be used to describe the amount of atoms, molecules, ions, electrons, other particles, or specified groups of such particles.

Fionna Shue 4L

A mmol is a "millimole", and a "milli-" is a factor of 10^-3. So 1 mmol = 10^-3 mol.

Fionna Shue 4L

If you know the frequency (v), you can find the energy using the equation E=hv where h=6.626*10^-34 J.s. If you know the wavelength (λ), you can find the energy using the equation E=hc/λ where c=2.997*10^8m.s^-1.

Fionna Shue 4L

I would use the value that is given on the periodic table that you are referring to. For our tests, we'll be given a periodic table and the answers will be based off of the sig figs on that periodic table.

Fionna Shue 4L

Use the value that is given in the periodic table that you are referring to and then round the final answer to the correct number of sig figs.

Fionna Shue 4L

The least number of sig figs in any number of the problem determines the number of significant figures in the answer. Trailing zeroes behind a decimal point will count as sig figs. For example, 6.48 / 2.16 = 3.00

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