CHEMISTRY COMMUNITY

Riya Shah 4H

For the first-order reaction A --> 3 B + C, when [A]0 = 0.015 mol/L, the concentration of B increases to 0.018 mol/L 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 0.030 m...

Riya Shah 4H

Did Lavelle go over the formula Q=It and the electrolysis process in detail? Some of the questions given as practice from the textbook talk about overpotential, did he teach it?

Riya Shah 4H

6th edition 14.5 (d)
How would you balance the following reaction in a basic medium -
P4 (s) ----> H2PO2 ^- (aq) + PH3 (g)

Riya Shah 4H

Do we need to know how to derive the rate laws?

Riya Shah 4H

If anyone has got their test back, could you please solve the question about deprotonation of H2O? Or if you remember how you did it, please answer.

Riya Shah 4H

(a) Since it is a first-order reaction, the rate constant k=[A]^1 and in terms of loss of A, you can just put a negative sign and say that it is decreasing.

(b) I am not sure about this one but would like to know the answer.

Riya Shah 4H

Yep, the temperature is always in Kelvin.

Riya Shah 4H

You can look at it this way - If a compound has more energy, its constituent atoms will have more energy. This energy will allow atoms to move around or break apart from each other thus making the compound unstable. Think of this situation as a kid who is hyped up on sugar, he or she will not sit qu...

Riya Shah 4H

I think this is because carbon is naturally found as graphite which is a solid.

Riya Shah 4H

Everything beginning from Gibbs free energy up to Friday's lecture which covered cell potential, electric work, and free energy.

Riya Shah 4H

yes, there is homework due every week unless mentioned by your TA or Dr. Lavelle.

Riya Shah 4H

A constant-volume calorimeter was calibrated by carrying out a reaction known to release 3.50 kJ of heat in 0.200 L of solution in the calorimeter (q =-3.50 kJ), resulting in a temperature rise of 7.32 C. In a subsequent experiment, 100.0 mL of 0.200 m HBr(aq) and 100.0 mL of 0.200 m KOH(aq) were mi...

Riya Shah 4H

Which one occurs at constant pressure - reversible or irreversible expansion?

Riya Shah 4H

A calorimeter is an isolated system so change in internal energy is always zero because neither there is a change in heat (q=0) nor there is any change in volume (w=0).

Riya Shah 4H

C v,m signifies the specific heat capacity of a gas at constant volume per mole, and C p,m signifies the same for constant pressure per mole.

Riya Shah 4H

Because solids and liquids can be called 'incompressible'. It means that their volume varies very little or not at all with change in pressure.

Riya Shah 4H

Calculate the heat released by 5.025 g of Kr(g) at 0.400 atm as it cools from 97.6 C to 25.0 C at
(a) constant pressure and
(b) constant volume. Assume that krypton behaves as an ideal gas.

Could someone please explain this?

Riya Shah 4H

I am assuming that we will have to use that in solving questions because he posted a document with rules of differentiation on his website.

Riya Shah 4H

The negative sign indicates that work is being done by the system, i.e. it is releasing energy.

Riya Shah 4H

Is enthalpy calculated only for reactions at constant pressure?

Riya Shah 4H

I don't think that any system except the universe is 100% isolated. But examples of an isolated system can be water in an insulated bottle.

Riya Shah 4H

Are the modules on Dr. Lavelle's website compulsory?

Riya Shah 4H

a diatomic molecule is a molecule like N2, O2, HCl, which has only 2 elements.

Riya Shah 4H

hello, he started thermochemistry and introduced enthalpy. he said that enthalpy is a state property meaning that it does not depend on the path taken but only on the initial condition. he also talked about enthalpies of fusion (solid -> liquid), sublimation (solid -> gas), and vaporization (liquid ...

Riya Shah 4H

Consider the equilibrium 3 NH3(g) + 5 O2(g) (equilibrium sign) 4 NO(g) + 6 H2O(g). (a) What happens to the partial pressure of NH3 when the partial pressure of NO is increased? (b) Does the partial pressure of O2 decrease when the partial pressure of NH3 is decreased? Can someone please help me with...

Riya Shah 4H

Not always. Sometimes decreasing the volume causes the pressure to increase since both of them are inversely proportional to each other.

Riya Shah 4H

So if you are given a pKa value of a conjugate acid which is large, does that mean the base is strong?

Riya Shah 4H

(a) A sample of 2.0 mmol Cl2(g) was sealed into a 2.0-L reaction vessel and heated to 1000. K to study its dissociation into Cl atoms. Use the information in Table 11.2 to calculate the equilibrium composition of the mixture. (b) If 2.0 mmol F2 was placed into the reaction vessel instead of the chlo...

Riya Shah 4H

I am not completely sure, but if the ions are in their aqueous states as products you just include them as you would include any compound or molecule in the equation for K.

Riya Shah 4H

It equals to -RT ln K. So If Gr is negative, then ln K must be positive and therefore K > 1; products are favored at equilibrium.
If Gr is positive, then ln K must be negative and therefore K < 1; reactants are favored at equilibrium.

Riya Shah 4H

While reading the textbook I came across the vant Hoff equation and it seems really confusing. How important is it for this course?

Riya Shah 4H

For the reaction PCl5(g) (equilibrium arrow) PCl3(g) + Cl2(g), Kc = 1.1 X 10^-2 at 400. K. (a) Given that 1.0 g of PCl5 is placed in a 250.-mL reaction vessel, determine the molar concentrations in the mixture at equilibrium. (b) What percentage of the PCl5 has decomposed at equilibrium at 400. K? C...

Riya Shah 4H

If I have 6 mols of Cl in a molecule, how many atoms does that convert to? Do we multiply 6 by Avogadro's number?

Riya Shah 4H

When do we use chloro and chlorido? What is the difference between the two

Riya Shah 4H

Naming is always done in an alphabetical order irrespective of the formula. It doesn't matter how we write the formula.

Riya Shah 4H

Are we supposed to do any calculations related to the formula Ep is directly proportional to polarizability1 times polarizability2 divided by r^6?

Riya Shah 4H

CH3CO2^- + H2O ---> OH^- + CH3CO2H

Which one is the conjugate acid-base pair?

Riya Shah 4H

Why is BrF3 sp3d hybridized?

Riya Shah 4H

So does it use a straight grading scale? Like top 3% get a + and bottom 3% get a - grade in whichever zone they fall into?

Riya Shah 4H

Is there any worksheet for test 3?

Riya Shah 4H

What is the trend of polarizing power for cations and anions?

Riya Shah 4H

Shielding effect is when electrons in the shells closer to the nucleus block the effect of the protons in the nucleus on other electrons in the outer shells.

Riya Shah 4H

Because of repulsion between the electrons in the given atoms.

Riya Shah 4H

Because the shape of a molecule is the arrangement of atoms in a manner that each experiences the least amount of repulsion. Hence, if repulsion is less, the strength is more.

Riya Shah 4H

Yes, molecules with see-saw shape usually have lone pairs.

Riya Shah 4H

Are we supposed to remember bond angles?

Riya Shah 4H

So in such cases do we consider C as the central atom or Be? Do have to take into account and write both the shapes?

Riya Shah 4H

Does dsp^3 mean that the s and p orbitals used are from a shell higher than the d? For example, when 3d, 4s, and 4p are involved in hybridization we say dsp^3?

Riya Shah 4H

What is the shortest wavelength we can observe for objects using the De Broglie equation?

Riya Shah 4H

Hi, can someone please help me with this question - A student prepared a solution of sodium carbonate by adding 2.111 g of the solid to a 250.0-mL volumetric flask and adding water to the mark. Some of this solution was transferred to a buret. What volume of solution should the student transfer into...

Riya Shah 4H

Do we learn about Molecular Orbital Theory in 14A?

Riya Shah 4H

How do we know which Lewis structure is correct and whether we have to add a double bond or not?

Riya Shah 4H

In ClO4- would all four oxygen atoms have a formal charge of -1?

Riya Shah 4H

Do we have to make dots according to how they fill the px, py, pz orbitals? For example, if px and py each have 1 electron then do they have to be singly represented around the atom?

Riya Shah 4H

Thank you so much! Are you going to post more midterm practice worksheets? Where can we get more practice problems from? LYNDON: I will not be posting more practice worksheets. I do hand out paper copies of practice at my normal session workshops. However, you can only get previous ones from student...

Riya Shah 4H

How can we know whether a bond has a covalent and ionic character?

Riya Shah 4H

What is the syllabus for the midterm that is on 5th November 2018?

Riya Shah 4H

Dr. Lavelle said that everything in outline 2 leading upto today will be on the test.

Riya Shah 4H

What is the significance of the equation E is directly proportional to q1q2/r ?

Riya Shah 4H

Because the energy of an electromagnetic radiation can never be negative. The energy emitted by an object (here, radiation) is always positive.

Riya Shah 4H

If electron affinity is negative then does that mean that the atom accepts electron easily and vice-versa meaning if electron affinity is positive the atom has difficulty accepting an electron?

Riya Shah 4H

How important is it to know the Schrodinger Equation because it can be very confusing?

Riya Shah 4H

So when we say 2NaCl we are referring to 2 formula units of NaCl? Calculating formula units is a little confusing too. Could someone please explain it?

Riya Shah 4H

So how many sigfigs are there in 705.0090 ??

Riya Shah 4H

Thank you so much Ashley! I will definitely be taking your advice.

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