Search found 36 matches

by Alondra
Sun Feb 23, 2020 9:56 pm
Forum: Balancing Redox Reactions
Topic: Reduction?
Replies: 13
Views: 122

Re: Reduction?

Here's a chart that may help! Also, remember OILRIG.

Oxidation is loss of electrons

Reduction is gain of electrons
by Alondra
Sun Feb 23, 2020 9:43 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: equilibrium concentrations
Replies: 7
Views: 84

Re: equilibrium concentrations

The unit for concentration is mol/L sometimes they'll give you n (moles) and v (volume in liters) separately so make sure you divide (n/v).
by Alondra
Sun Feb 23, 2020 9:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ph
Replies: 8
Views: 92

Re: Ph

It is always given at equilibrium so just do 10^-pH to find the concentration of H+.
by Alondra
Sun Feb 23, 2020 9:35 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Going from pKa to pH
Replies: 10
Views: 167

Re: Going from pKa to pH

The image I attached explains the relationship between pka,pkb,pH and pOH.
by Alondra
Sun Feb 23, 2020 9:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: What to exclude in K
Replies: 9
Views: 85

Re: What to exclude in K

Include H20 when it's a gas and exclude it if the phase is different (solid/liquid).
by Alondra
Sun Feb 16, 2020 10:13 pm
Forum: Phase Changes & Related Calculations
Topic: Delta H Fusion
Replies: 9
Views: 199

Re: Delta H Fusion

Multiple steps are used because the substance undergoes different steps, for instance, the temperature rises and then there's a phase change from solid to liquid.
by Alondra
Sun Feb 16, 2020 10:09 pm
Forum: Phase Changes & Related Calculations
Topic: Heating curve
Replies: 5
Views: 159

Re: Heating curve

Phase changes --> use q=m(delta H)

Temperature change --> use q= mCAT
by Alondra
Sun Feb 16, 2020 9:59 pm
Forum: Phase Changes & Related Calculations
Topic: Equation Choice
Replies: 5
Views: 194

Re: Equation Choice

Phase changes: solid --> liquid (fusion), liquid --> gas (vaporization), solid --> gas (sublimation) or vice versa : melting, condensation, deposition.

The chart may help you with knowing what equation to use
by Alondra
Sun Feb 16, 2020 9:48 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibb's Free Energy
Replies: 7
Views: 78

Re: Gibb's Free Energy

This refers to the energy available to do work.
by Alondra
Sun Feb 16, 2020 7:46 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Constant Pressure and Volume
Replies: 6
Views: 121

Re: Constant Pressure and Volume

Constant pressure: for monatomic it’s 5R/2; for diatomic it’s 7R/2


Constant volume: for monatomic it’s 3R/2; for diatomic it’s 5R/2
by Alondra
Sun Feb 16, 2020 7:36 pm
Forum: Phase Changes & Related Calculations
Topic: Phase changes
Replies: 8
Views: 167

Re: Phase changes

When the substance reaches it’s melting/ boiling/ freezing point. Drawing the heating curve for water at least can be helpful.
by Alondra
Sun Feb 09, 2020 11:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q and K
Replies: 3
Views: 44

Re: Q and K

K is a ratio that represents the system at equilibrium while Q is at any given state. you compare them to know whether the forwards (products) or reverse (reactants) rxn will be favored.
by Alondra
Sun Feb 09, 2020 11:36 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Cv vs. Cp
Replies: 5
Views: 52

Re: Cv vs. Cp

Cv is used for systems with constant volume; Cv= (3/2)R, if diatomic then Cv= (5/2)R

Cp is used for systems with constant pressure; Cp = (5/2)R, if diatomic then Cv= (7/2)R
by Alondra
Sun Feb 09, 2020 11:20 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat capacity
Replies: 3
Views: 25

Re: Heat capacity

Heat Capacity is intensive because it does not depend on a particular amount of a substance.

Specific/molar heat capacity is extensive because it's a value in relation to a particular amount of a substance.
by Alondra
Sun Feb 09, 2020 11:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy change
Replies: 3
Views: 40

Re: Enthalpy change

The sign is negative for a reverse rxn.
by Alondra
Sun Feb 09, 2020 11:07 pm
Forum: Phase Changes & Related Calculations
Topic: heat added/released
Replies: 6
Views: 61

Re: heat added/released

If there is no delta H + or - stated in the problem then look at the products and reactants in the rxn and consider bonds being formed or broken.
by Alondra
Sun Feb 02, 2020 11:52 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat capacities of different compounds
Replies: 3
Views: 25

Re: Heat capacities of different compounds

Heat capacity refers to the amount of heat added to/released from a system.

Specific heat capacity refers to the heat capacity of a system per gram of the substance.

In order to determine which has more you should look at the mass and its chemical composition.
by Alondra
Sun Feb 02, 2020 11:40 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: w = -P*delta V
Replies: 4
Views: 28

Re: w = -P*delta V

The negative sign is part of the equation. However, the work input or output differs depending on the pressure and change in volume.
by Alondra
Sun Feb 02, 2020 11:28 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Delta q and delta h
Replies: 5
Views: 42

Re: Delta q and delta h

Delta Q refers to the amount of heat transferred to a system (heat input)

Delta H is the state of the system, which describes the change in enthalpy (energy of a system)
by Alondra
Sun Feb 02, 2020 11:19 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: State Function
Replies: 4
Views: 37

Re: State Function

Internal energy is a specific value that reflects the state of the system. On the other hand, work and heat are path functions because the magnitude depends on the process/ path taken.
by Alondra
Sun Feb 02, 2020 11:07 pm
Forum: Phase Changes & Related Calculations
Topic: Relevance of Phase Changes
Replies: 9
Views: 69

Re: Relevance of Phase Changes

This is important when calculating enthalpy because energy is used for a phase change as well as temperature.
by Alondra
Sun Jan 26, 2020 10:22 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy
Replies: 3
Views: 33

Re: Enthalpy

Enthalpy depends on the initial and final values of the reaction. It does not take into account the path taken to arrive to such destination.
by Alondra
Sun Jan 26, 2020 10:18 pm
Forum: Phase Changes & Related Calculations
Topic: Work (w)
Replies: 8
Views: 67

Re: Work (w)

Work can be thought as the force or energy applied to something. Since the value of this force/energy varies by object it cannot be consider a state property.
by Alondra
Sun Jan 26, 2020 7:52 pm
Forum: Phase Changes & Related Calculations
Topic: Phase changes: endothermic vs exothermic
Replies: 12
Views: 172

Re: Phase changes: endothermic vs exothermic

Yes! Reverse rxns are exothermic!

Exothermic: condensation, freezing, deposition

Endothermic: vaporization, melting, sublimation
by Alondra
Sun Jan 26, 2020 7:49 pm
Forum: Phase Changes & Related Calculations
Topic: Phase Changes
Replies: 2
Views: 18

Re: Phase Changes

Yes! The reverse reactions: vaporization and it’s opposite -> condensation, melting and it’s opposite-> freezing, sublimation and it’s opposite-> deposition.
by Alondra
Sun Jan 26, 2020 7:41 pm
Forum: Phase Changes & Related Calculations
Topic: State Property
Replies: 3
Views: 18

Re: State Property

Enthalpy does not dependent on the path taken to obtain that state. An example of a state property would be pressure. However, work and heat are not state properties.
by Alondra
Mon Jan 20, 2020 1:29 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH for weak acids
Replies: 5
Views: 235

Re: pH for weak acids

I think of acids as having more protons and a lower value in the 0-14 range while bases have less protons and a higher value.
by Alondra
Mon Jan 20, 2020 1:20 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6B.9
Replies: 3
Views: 114

Re: 6B.9

I think on the class website there's a sheet about some errors in the solution manual. Not so sure though.
by Alondra
Sun Jan 19, 2020 6:56 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Molar concentration of acids & bases
Replies: 8
Views: 129

Molar concentration of acids & bases

If you're asked about the molar concentration of H30+ or OH- would you leave the answer as just the concentration with units mol.L^-1 or do you have to define this concentration as logarithms (pH=-log[H30+] and pOH-log[OH-])?
by Alondra
Sun Jan 19, 2020 6:42 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH range
Replies: 4
Views: 111

Re: pH range

Yes, the range is 0-14. This is rare but it shows that it is either a very strong acid/base.
by Alondra
Sun Jan 19, 2020 5:57 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Approximation
Replies: 6
Views: 117

Re: Approximation

I believe this has to do with the value being so small that it barely even causes a minimal change on a bigger initial concentration.
by Alondra
Sun Jan 12, 2020 8:24 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: predicting effects
Replies: 9
Views: 149

Re: predicting effects

The amount of NO2 is increased because the system will try to reach equilibrium. After removing one product there is essentially more reactants than products, which I beleive causes the forward reaction to be favored.
by Alondra
Sun Jan 12, 2020 8:19 pm
Forum: Ideal Gases
Topic: partial pressures
Replies: 7
Views: 70

Re: partial pressures

K is a constant. I believe a change in pressure does not affect K but a change in temperature can.
by Alondra
Sun Jan 12, 2020 8:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: stoichiometric coefficients
Replies: 5
Views: 54

Re: stoichiometric coefficients

Stoichiometric coefficients are not always the same values in an equation. It only shows the number of molecules present and from there you have to make sure that it's balanced. In the expression for K these appear as exponents.
by Alondra
Sun Jan 12, 2020 8:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Comparing K
Replies: 9
Views: 75

Comparing K

What is the difference between K<1/K>1 and K>10^3/K<10^-3? In what context do these apply?
by Alondra
Sun Jan 12, 2020 6:25 pm
Forum: Ideal Gases
Topic: P=(n/v)RT
Replies: 12
Views: 123

Re: P=(n/v)RT

I believe this depends on your given values and what you are trying to find.The equation is rearranged to find Kc. (P=nRT/V = n/V x RT = conc x RT)

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