Search found 63 matches

by Dhwani Krishnan 1G
Sat Mar 16, 2019 12:08 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.13
Replies: 1
Views: 19

9.13

During the test of an internal combustion engine, 3.00 L of nitrogen gas at 18.5 C was compressed suddenly (and irreversibly) to 0.500 L by driving in a piston. In the process, the temperature of the gas increased to 28.1 C. Assume ideal behavior. What is the change in entropy of the gas? How can yo...
by Dhwani Krishnan 1G
Thu Mar 14, 2019 11:08 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: A in the Arrhenius Equation
Replies: 4
Views: 22

Re: A in the Arrhenius Equation

it is the frequency factor, and basically gives the frequency with which reactants will collide in the correct orientation in order to form product.
by Dhwani Krishnan 1G
Thu Mar 14, 2019 11:01 pm
Forum: General Rate Laws
Topic: Final
Replies: 9
Views: 63

Re: Final

I don't think so, but on previous exams/midterm sig figs weren't counted for every problem, only for 1-2
you always need the correct units though!
by Dhwani Krishnan 1G
Thu Mar 14, 2019 11:00 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Overall Order
Replies: 5
Views: 35

Re: Overall Order

you can use it to determine how the overall rate will change with a change in reactant concentration
by Dhwani Krishnan 1G
Mon Mar 11, 2019 11:36 am
Forum: General Rate Laws
Topic: Are coefficients in rate laws?
Replies: 2
Views: 23

Re: Are coefficients in rate laws?

They don't affect the rate law itself, but do effect the value of k as you need to know the ratio of moles produced/used during the reaction to find k.
by Dhwani Krishnan 1G
Mon Mar 11, 2019 11:34 am
Forum: Ideal Gases
Topic: Ideal gases
Replies: 5
Views: 39

Re: Ideal gases

For the most part, yes. The questions should say "assume ideal behavior."
by Dhwani Krishnan 1G
Mon Mar 11, 2019 11:32 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Constanst
Replies: 3
Views: 25

Re: Equilibrium Constanst

the units on the rate constant k must ensure that the overall units for the rate is (g/mol)/s.
by Dhwani Krishnan 1G
Mon Mar 04, 2019 4:15 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 6th edition example 14.8
Replies: 1
Views: 18

Re: 6th edition example 14.8

No. Ecell = Ecath - Eanode, where the E values are for the reduction reaction (so you don't make anything negative), which is the method used in the book. Ecell = Ecath + Ean when you add the actual potentials for each half-reaction. Either method will yield the same answer.
by Dhwani Krishnan 1G
Sun Feb 24, 2019 9:07 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Spontaneous?
Replies: 13
Views: 86

Re: Spontaneous?

Enthalpy doesn't really show spontaneity, except that exothermic reactions are generally spontaneous because delta S is usually positive for these reactions.

A positive entropy generally indicates a spontaneous process, but only with a negative delta G can you be sure.
by Dhwani Krishnan 1G
Sun Feb 24, 2019 9:05 pm
Forum: Balancing Redox Reactions
Topic: Hydrogen?
Replies: 3
Views: 28

Re: Hydrogen?

Hydrogen has only 1 valence electron. When combined with a less-electronegative element (eg. a metal), it gains another to complete its p-orbital, giving it an oxidation state of -1. In other cases, it loses its electron, giving it an oxidation state of +1. Since there is only 1 electron to begin wi...
by Dhwani Krishnan 1G
Sun Feb 24, 2019 9:02 pm
Forum: Balancing Redox Reactions
Topic: Balancing Redox Reactions
Replies: 1
Views: 15

Re: Balancing Redox Reactions

First, write out the half-reactions and balance each as you normally would. Then, balance it so the charges on both sides add up to the same number.
by Dhwani Krishnan 1G
Sun Feb 24, 2019 12:36 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneous with Temperature Increase?
Replies: 2
Views: 31

Spontaneous with Temperature Increase?

Can a nonspontaneous process with a positive deltaS become spontaneous if the temperature is increased (assuming that deltaH and deltaS are both independent of temperature)?
by Dhwani Krishnan 1G
Wed Feb 20, 2019 4:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 3
Views: 27

Re: Salt Bridge

what is the difference between a salt bridge and porous disk?
by Dhwani Krishnan 1G
Wed Feb 20, 2019 4:12 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anode v. Cathode
Replies: 9
Views: 82

Re: Anode v. Cathode

what is the difference between an anode and cathode?
by Dhwani Krishnan 1G
Wed Feb 20, 2019 4:11 pm
Forum: Balancing Redox Reactions
Topic: Separating the equation
Replies: 5
Views: 33

Re: Separating the equation

Why would you separate the equation? Like how would this make it easier?
by Dhwani Krishnan 1G
Sun Feb 10, 2019 6:27 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: when to use kj and kj.mol^-1
Replies: 2
Views: 39

Re: when to use kj and kj.mol^-1

enthalpies of formation are always given /mol. As for reaction enthalpies, I believe that they're generally given in just kJ because it's for the entire reaction (so there are multiple moles of substances used).
by Dhwani Krishnan 1G
Sun Feb 10, 2019 6:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy of Phase Changes
Replies: 4
Views: 40

Re: Enthalpy of Phase Changes

More and more energy (heat) is required to attain higher energy phases because you have to separate the molecules more. in terms of energy, solids < liquids < gases. Therefore, the enthalpy of fusion is less than that of vaporization.
by Dhwani Krishnan 1G
Sun Feb 10, 2019 6:23 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Problem #8.59 (Sixth Edition)
Replies: 3
Views: 33

Re: Problem #8.59 (Sixth Edition)

The standard enthalpy of formation for N2 is 0! All elements in their standard states (N2, O2, etc.) have a standard enthalpy of formation of 0
by Dhwani Krishnan 1G
Sat Feb 02, 2019 9:26 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Compression of Gas
Replies: 4
Views: 53

Re: Compression of Gas

why does work being done correlate to heat being added?
by Dhwani Krishnan 1G
Sat Feb 02, 2019 9:25 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: delta H vs q
Replies: 9
Views: 87

delta H vs q

What is the difference between and q? How are they related?
by Dhwani Krishnan 1G
Sat Feb 02, 2019 9:21 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: U=q+w
Replies: 3
Views: 37

Re: U=q+w

Delta U is the change in internal energy of a system. The equation states that Delta U is equal to the heat lost/gained (q) plus the work done on or by the system (w). This is because the only way for a system to lose internal energy is through heat or work.
by Dhwani Krishnan 1G
Sun Jan 27, 2019 9:18 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Ph and Pka
Replies: 5
Views: 51

Re: Ph and Pka

You could use Pka and an ICE table if necessary to find [H3O+].
by Dhwani Krishnan 1G
Sun Jan 27, 2019 9:15 pm
Forum: Phase Changes & Related Calculations
Topic: Steam v. Boiling Water
Replies: 4
Views: 43

Re: Steam v. Boiling Water

The energy to boil water is (energy to melt) + (energy to boil).
The energy to have steam is (energy to boil) + (energy to vaporize)

Therefore, more energy (and thus, more heat) is required to form steam, which is why the burns are more severe.
by Dhwani Krishnan 1G
Sun Jan 27, 2019 9:12 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard Enthalpy
Replies: 1
Views: 21

Re: Standard Enthalpy

Dr. Lavelle said in class that those values will be given.
by Dhwani Krishnan 1G
Mon Jan 21, 2019 12:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: buffer questions on test
Replies: 7
Views: 81

Re: buffer questions on test

What exactly do we need to know about them?
by Dhwani Krishnan 1G
Mon Jan 21, 2019 12:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kp vs Kc
Replies: 7
Views: 61

Re: Kp vs Kc

If all the reactants/products are gases, it doesn't matter which you use. However, Kc and Kp are not always equal! This is due to concentration and Pressure being related via the Ideal Gas Law (PV = nRT) This link explains the technicalities of it well: https://chem.libretexts.org/Bookshelves/Physic...
by Dhwani Krishnan 1G
Mon Jan 21, 2019 12:17 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Buffer Solutions
Replies: 2
Views: 45

Re: Buffer Solutions

Buffer solutions are used to keep the pH constant. To my understanding, you don't "ignore" the salt, but because it is a buffer, it doesn't affect pH / affect [H3O+] and factor into the ICE table.
by Dhwani Krishnan 1G
Sun Jan 13, 2019 6:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Tables
Replies: 2
Views: 51

Re: ICE Tables

For A\rightleftharpoons B + C To make an ICE table, first enter all the numbers you are given into the table, and add in 0 in the "Initial" column if they're not given and there's no way to calculate it (you would be able to calculate it if you have Q, for example). If you're given an equi...
by Dhwani Krishnan 1G
Sun Jan 13, 2019 6:12 pm
Forum: Ideal Gases
Topic: Definition of an Ideal Gas [ENDORSED]
Replies: 2
Views: 30

Definition of an Ideal Gas [ENDORSED]

What are the conditions for an Ideal Gas in terms of Temperature/Pressure/Volume etc?
by Dhwani Krishnan 1G
Sun Jan 13, 2019 6:11 pm
Forum: Ideal Gases
Topic: Pressure and Temperature [ENDORSED]
Replies: 2
Views: 69

Pressure and Temperature [ENDORSED]

According to the Ideal Gas Law, P = nRT/V. Therefore, P and T are directly proportional. My question is, conceptually, how/why does an increase in Pressure cause and increase in Temperature and vice-versa?
by Dhwani Krishnan 1G
Sun Dec 09, 2018 4:38 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Why HF is a weaker acid than HCl
Replies: 11
Views: 140

Re: Why HF is a weaker acid than HCl

By that same logic, would HClO2 be weaker than HClO3?
by Dhwani Krishnan 1G
Fri Dec 07, 2018 12:17 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH for strong acids [ENDORSED]
Replies: 2
Views: 47

Re: pH for strong acids [ENDORSED]

It can be assumed that given a strong acid, it completely dissociates in solution, and therefore the pH is -log[H3O+] (we don't have to worry about the Ka values or anything like that).
by Dhwani Krishnan 1G
Fri Dec 07, 2018 12:14 am
Forum: Amphoteric Compounds
Topic: Definition
Replies: 6
Views: 93

Re: Definition

Yes -an amphoteric substance like water would act like a base or an acid depending on what it is reacting with.
by Dhwani Krishnan 1G
Tue Dec 04, 2018 9:21 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Denticity from lewis structure or VSEPR
Replies: 1
Views: 32

Denticity from lewis structure or VSEPR

Is there a way to tell denticity of a ligand from its lewis structure or VSEPR shape? How do you find denticity otherwise?
by Dhwani Krishnan 1G
Sun Dec 02, 2018 10:50 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Acid + Base Reaction
Replies: 1
Views: 38

Acid + Base Reaction

Do all bases neutralize acids and vice-versa? Or does the strength of the acid/base affect how they react?
by Dhwani Krishnan 1G
Sun Dec 02, 2018 10:49 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Water
Replies: 4
Views: 47

Water

Does water have a neutral pH because it can act as an acid or base depending on the situation?
by Dhwani Krishnan 1G
Sun Dec 02, 2018 10:45 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: "Bronsted" and "Lewis" Interchangability
Replies: 2
Views: 49

Re: "Bronsted" and "Lewis" Interchangability

But both Bronsted and Lewis acids dissociate into Hydronium ions in water, correct?
by Dhwani Krishnan 1G
Sun Dec 02, 2018 10:39 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: "Bronsted" and "Lewis" Interchangability
Replies: 2
Views: 49

"Bronsted" and "Lewis" Interchangability

Are all Lewis acids bronsted acids and vice-versa? Is the same true for Bases?
by Dhwani Krishnan 1G
Sun Dec 02, 2018 10:34 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Biological Compounds
Replies: 3
Views: 55

Re: Biological Compounds

it wouldn't make sense for a Nitrogen lone pair to act as an acid, as acids are e- pair acceptors by definition, not donors.
by Dhwani Krishnan 1G
Sun Dec 02, 2018 10:33 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Acids for final
Replies: 2
Views: 73

Re: Acids for final

Probably the ones mentioned in class -- Carboxylic as the most common Organic acid, HBr/HCl/etc as strong acids, and CH3COOH (acetic) as an example of a weak acid
For bases, you should probably know the Alkali/Alkaline Earth metals as strong bases and NH3/Ammines as weak bases
by Dhwani Krishnan 1G
Wed Nov 21, 2018 11:28 am
Forum: Hybridization
Topic: Hybrid orbitals pointing to corners?
Replies: 4
Views: 75

Re: Hybrid orbitals pointing to corners?

Because of electron repulsion, to maximize distance the orbitals end up "pointing to the corners."
by Dhwani Krishnan 1G
Wed Nov 21, 2018 11:24 am
Forum: Hybridization
Topic: Sp3
Replies: 2
Views: 47

Re: Sp3

there are 3 p-orbitals, each holding up to 2e-, for a total of 6 electrons, not 6 orbitals.
by Dhwani Krishnan 1G
Wed Nov 21, 2018 11:22 am
Forum: Hybridization
Topic: What is s-character of an orbital? (6th ed, 4.43)
Replies: 1
Views: 37

What is s-character of an orbital? (6th ed, 4.43)

The question reads, "Noting that the bond angle of an sp3 hybridized atom is 109.5 and that of an sp2 hybridized atom is 120, do you expect the bond angle between two hybrid orbitals to increase or decrease as the s-character of the hybrids is increased?" What is the s-character of a hybri...
by Dhwani Krishnan 1G
Sun Nov 11, 2018 12:51 pm
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 9
Views: 214

Re: Bond Length

I don't think so. By definition, single bonds are generally longer than double bonds, especially between the same elements.
by Dhwani Krishnan 1G
Sun Nov 11, 2018 12:50 pm
Forum: Dipole Moments
Topic: Polarizable vs Polarizing Ability
Replies: 3
Views: 73

Polarizable vs Polarizing Ability

What is the difference between these two terms, and what they have to do with electronegativity?
by Dhwani Krishnan 1G
Sun Nov 11, 2018 12:32 pm
Forum: Bond Lengths & Energies
Topic: VSEPR Model for Water
Replies: 3
Views: 58

VSEPR Model for Water

Why isn't H2O a linear molecule, but CO2 (for example) is? How do we know the bond angle isn't 180?
by Dhwani Krishnan 1G
Sat Nov 03, 2018 10:26 am
Forum: Lewis Structures
Topic: Resonance Structures
Replies: 1
Views: 47

Resonance Structures

I'm still a little confused on how to find resonance structures. How can you tell how many resonance structures a molecule has / which structure is the most stable?
by Dhwani Krishnan 1G
Sat Nov 03, 2018 10:22 am
Forum: Ionic & Covalent Bonds
Topic: Delta Negative
Replies: 2
Views: 32

Re: Delta Negative

When atoms covalently bonded unequally share electrons (occurs in any bond with atoms of different elements), the more electronegative atom "pulls" the shared e- towards them, giving that side of the molecule a slight negative charge. Similarly, the less electronegative atom ends up with a...
by Dhwani Krishnan 1G
Sat Nov 03, 2018 10:17 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Nickel/Vanadium alternate configuration
Replies: 1
Views: 52

Nickel/Vanadium alternate configuration

I understand why Chromium and Copper don't follow the electron configuration pattern, but my question is, why do Vanadium and Nickel? Their electron configurations are [Ar]3d3 4s2 and [Ar]3d8 4s2 respectively, but wouldn't [Ar]3d5 and [Ar]3d10 be more stable? Or is it because they need electrons in ...
by Dhwani Krishnan 1G
Sun Oct 28, 2018 9:45 pm
Forum: Lewis Structures
Topic: Lewis Structure for Compounds
Replies: 6
Views: 95

Lewis Structure for Compounds

In Class, Dr. Lavelle mentioned that you should not draw 2 cations next to each other when drawing the lewis dot structure of an ionic compound. Why is that?
by Dhwani Krishnan 1G
Sun Oct 28, 2018 9:40 pm
Forum: Ionic & Covalent Bonds
Topic: Variable Valence
Replies: 2
Views: 28

Re: Variable Valence

Why do they have a tendency to form multiple ions? Also, are elements that form ions w/ variable valence all transition metals?
by Dhwani Krishnan 1G
Sun Oct 28, 2018 9:37 pm
Forum: Ionic & Covalent Bonds
Topic: Atomic Radius Decreasing
Replies: 2
Views: 22

Atomic Radius Decreasing

I'm still confused as to why atomic radius decreases across a period. Shouldn't more electrons being added to new orbitals increase the size?
by Dhwani Krishnan 1G
Sat Oct 20, 2018 5:59 pm
Forum: Properties of Light
Topic: Photoelectric Effect result
Replies: 2
Views: 56

Photoelectric Effect result

How was the fact that long wavelengths, regardless of intensity, could not eject an e-, but shorter wavelengths could used to determine that light can be quantized as photons? What is the reasoning behind this conclusion?
by Dhwani Krishnan 1G
Sat Oct 20, 2018 5:57 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: energy difference vs. E subscript n
Replies: 2
Views: 61

Re: energy difference vs. E subscript n

So to calculate deltaE from, for example, the second to the first energy level, it would be E(subscript)2 - E1?
by Dhwani Krishnan 1G
Sat Oct 20, 2018 5:52 pm
Forum: Properties of Light
Topic: Atomic Spectra
Replies: 3
Views: 69

Re: Atomic Spectra

Do emission and absorption spectra look the same? Or are they "opposites" of each other?
by Dhwani Krishnan 1G
Sun Oct 14, 2018 3:58 pm
Forum: Properties of Light
Topic: Speed of Light
Replies: 18
Views: 170

Re: Speed of Light

the speed of light changes with the medium, in air it is 3.0x10^8m/s.
by Dhwani Krishnan 1G
Sun Oct 14, 2018 3:52 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Balmer Series
Replies: 2
Views: 55

Re: Balmer Series

For the Balmer series, the lowest energy level (the final energy level) is n=2. The electron is falling from a higher energy level to n=2, but since it hasn't reached ground state, it is still excited. Energy is still given off.
by Dhwani Krishnan 1G
Sun Oct 14, 2018 3:47 pm
Forum: Properties of Electrons
Topic: Diffraction Patterns/Slit experiment
Replies: 1
Views: 48

Diffraction Patterns/Slit experiment

Do all dark bands correlate to destructive interference/light bands correlate to constructive interference? Why does this happen?
by Dhwani Krishnan 1G
Fri Oct 05, 2018 5:34 pm
Forum: Limiting Reactant Calculations
Topic: When to use H vs H2
Replies: 7
Views: 113

Re: When to use H vs H2

I also have a question: when you have a reaction in the form of MgSO4.7H2O where the 7 is in front of the H2O, would you have to do 7x(molar mass of H2) + the molar mass of O or 7x(the molar mass of H20)? Because 2 hydrogens are Bonded to 1 oxygen (to form water), the "7" is the coefficie...
by Dhwani Krishnan 1G
Fri Oct 05, 2018 5:29 pm
Forum: Properties of Light
Topic: Behavior of small objects - clarification
Replies: 3
Views: 54

Re: Behavior of small objects - clarification

I don't think it would be continuous. Because only 1 molecule is entering at a time, the amount of water is so small that the scale (as Leela said) would have "jumps" as it recalibrates. Another analogy would be when you don't close the sink tap fully, and one droplet at a time comes out -...
by Dhwani Krishnan 1G
Fri Oct 05, 2018 5:20 pm
Forum: SI Units, Unit Conversions
Topic: formula units [ENDORSED]
Replies: 68
Views: 21035

Re: formula units [ENDORSED]

Are salts the only compounds for which you use Formula Units as opposed to Molecule? Or is any compound with 2 different elements a Formula Unit?

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