×
Log in to StudySoup
Get Full Access to YSU - Study Guide - Midterm
Join StudySoup for FREE
Get Full Access to YSU - Study Guide - Midterm

Already have an account? Login here
×
Reset your password

YSU / Chemistry / CHEM 1515 / How to calculate concentration in a dilution?

How to calculate concentration in a dilution?

How to calculate concentration in a dilution?

Description

School: Youngstown State University
Department: Chemistry
Course: General Chemistry
Professor: Leskiw
Term: Fall 2018
Tags: General Chemistry, Study Guide, Midterm Study Guide, and midterm 2
Cost: 50
Name: Chem 1515 Midterm 2 Study Guide
Description: The study guide attached covers material from chapters 4, 10, and 5.
Uploaded: 10/21/2018
9 Pages 107 Views 4 Unlocks
Reviews

ccealy (Rating: )


ZCHoward (Rating: )



Chem 1515 Midterm 2 “Study Guide”


How to calculate concentration in a dilution?



Molarity 

∙ Concentration: The amount of a solute that is dissolved in a solvent ∙ Molarity (M): Moles of a solute dissolved per liter of solution

Dilutions 

Dilution: adding more solvent to a solution to reduce its concentration

∙ Creating a solution with more useful concentration from concentrated stock  solution

∙ Creating a series of a known dilutions to determine the concentration of an  unknown solution

Calculating Concentration in a Dilution

1. Use the desired volume and concentration to determine the number of moles  of solute in the solution desired [moles solute = M2V2] 


What defines a gas?



2. Using the concentration of the more concentrated solution calculate the  volume which corresponds to this number of moles [moles solute = M1V1]  3. Measure the volume of concentrated solution determined in step 2, and dilute to the desired volume We also discuss several other topics like What is sucrose?

The Easier Way

∙ When solvent is added it doesn’t change the number of moles of the solute,  therefor the moles should be the same before and after the dilution

M1V1 = M2V2

M1 = Molarity of concentrated solution

V1 = Volume of concentrated solution

M2 = Molarity of dilute solution

V2 = Volume of dilute solution


What is the standard molar enthalpy of formation?



Titrations 

∙ Titration: A substance that reacts with known stoichiometry with the  substance whose concentration is to be determined We also discuss several other topics like Who serves in congress?

∙ Standard Solution: A solution whose concentration is known very  accurately Don't forget about the age old question of What document is written and made up of many different enlightenment ideas?

∙ Equivalence point: point at which an exact stoichiometric ratio of standard  solution has been added to the unknown solution

Chem 1515 Midterm 2 “Study Guide”

Oxidation-Reduction Reactions 

Oxidation-Reduction (Redox) Reaction: 

 Reaction in which electrons are transferred from one atom to another ∙ In redox reactions it is the transfer of electrons which is the driving force for  the reaction

Oxidation and Reduction

Reduction:

 Gain of electrons by the reduced species

Oxidation:

 Loss of electrons by the oxidized species  

∙ In a Redox reaction the reduction of one atom will always be accompanied by  the oxidation of another

∙ Together these atoms are called the “Redox Pairs”

∙ A good way to remember what oxidation and reduction represent is o OIL RIG

o Oxidation Is Loss, Reduction Is Gain Don't forget about the age old question of What are the different kinds of intelligence?

Oxidizing and Reducing Agents

∙ In a redox pair we refer to the species that is causing the reduction as the  reducing agent, and the species causing the oxidation as the oxidizing agent ∙ Reducing Agent: 

Species causing the reduction. This will be the species being oxidized. ∙ Oxidation Agent: 

Species causing the oxidation. This will be the species being reduced. Common Oxidizing Agents 

1) Oxygen (O2)

2) Halogens

3) Hydrogen Peroxide (HOOH)

4) Nitric Acid (HNO3)

Common Reducing Agents Don't forget about the age old question of What makes myths traditional stories?
We also discuss several other topics like What were the highlights of the 19th century imperialism?

1) Group 1A and 2A metals

2) Transition metals

3) Hydrogen gas (H2)

4) Carbon (C)  

∙ Transition Metals can adopt multiple charge states and the cations are  have multiple oxidation states

∙ Transition meatal cations that can be further oxidized can act as a  reducing agent

Chem 1515 Midterm 2 “Study Guide”

Quantifying Redox Reactions 

Oxidation number: Charge of a combined atom relative to that of the uncombined atom

∙ The sum of the oxidation numbers must equal the sum of the charges in a  chemical equation

∙ When determining the oxidation number of an atom in a molecular compound treat it as if the compound were ionic following a few simple rules

Assigning Oxidation Numbers in Molecular Compounds

Rule 1: The oxidation number of a pure element is zero

Rule 2: The oxidation of a monatomic ion equals its charge

Rule 3: Certain elements will have the same oxidation number in virtually any  compound they are present in

o H will have an oxidation number of +1 unless it is bound only with a  metal in which case it will have an oxidation number of -1  

o O will have an oxidation number of -2 unless the compound is a  peroxide in which case it will have an oxidation number of -1

o F has an oxidation number of -1

o Halogens other than F have an oxidation number of -1 unless bound  to other halogens  

o In binary compounds group 6A elements (O, S, Se…) will have an  oxidation number of -2 unless bound to O or a halogen, in which case  their number will be positive

Rule 4: The sum of the oxidation numbers in a neural compound is zero

Rule 5: The sum of the oxidation numbers in a polyatomic ion is the charge of the  ion

Activity Series and Oxidation

∙ Metals lowest on the activity series are the worst reducing agents, but their  cations will be the strongest oxidizing agents

∙ The activity series thus not only lets us predict the strongest oxidizing agents, but also which ions will be the strongest oxidizing agents

What Defines a Gas: 

1. Gases do not have a fixed size nor shape, they expand to fill whatever  volume is available

2. Gases can be compressed

3. Gases exert pressure on whatever surrounds them

Chem 1515 Midterm 2 “Study Guide”

4. Gases mix completely and will not spontaneously separate  

5. Gases can be completely described by: pressure (P), temperature (T), volume  (V), and moles of a gas (n)

The Molecular View of Gases:  

Kinetic Molecular Theory:

1. Gas molecules are much smaller than the average distance between them. A  container of a gas is thus mostly empty space

2. Gas molecules are in constant random motion

3. Forces between the gas molecules are negligible except for collisions 4. Collisions between molecules are completely elastic

5. The average kinetic energy of a gas increase with increasing temperature The Effect of Molecular Mass on Molecular Velocity: 

∙ Average kinetic energy is related to temperature and therefor a more massive gas will have a lower average velocity than a less massive gas at the same  temperature

Pressure 

∙ P = F/A

∙ Force per unit area

∙ In a gas the force comes from the gas molecules striking the container and  the area is the surface area of the container

∙ The SI unit for pressure is the Pascal (Pa)

Measuring Pressure

∙ Atmospheric pressure can be measured using mercury barometer and the  resulting pressure is measured in mmHg, inHg or Torr

o 1 mmHg = 1 Torr

o 1 inHg = 25.4 mmHg

Standard Temperature and Pressure (STP)  

∙ We often refer to the properties of gasses at standard temperature and  pressure:

o 273K and 1 atm

The Gas Laws: 

Boyle’s Law: 

Pressure-Volume Relationships

Chem 1515 Midterm 2 “Study Guide”

∙ At constant temperature the pressure of a gas is inversely proportional to its  volume

o V = a/P

o PV = a

Charles’s Law: 

Temperature-Volume Relationships

∙ At constant pressure the volume of a gas is directly proportional to its  temperature

o V = bT 

o V/T = b

Avogadro’s Law:  

Molar-Volume Relationships

∙ At constant temperature and pressure, the volume of a gas is directly  proportional to the number of moles of gas present

The Ideal Gas Law 

Combination of Boyle’s, Charles’s, and Avogadro’s laws leads to the ideal gas law: PV = nRT 

Where: R = Ideal gas constant

R= 8.315 J/mol K

R = .08206 L atm/mol K

An ideal gas is any gas which obeys the ideal gas law. Most gasses behave nearly  ideal at room temperatures and pressures.

Combined Gas Laws 

Many problems can be solved by rearranging the ideal gas law to combine the  terms that are not changing during a process

∙ Ex: If the number of moles of a gas are constant while pressure, volume and  temperature are changing…  

o PV/T = nR so P1V1/T1 = P2V2/T2

Molar Masses and Gas Density

Chem 1515 Midterm 2 “Study Guide”

The Ideal Gas Law can also be used to relate molar mass and the density of the  gas:

PV = nRT 

PV = mRT/M (m – mass, M = molar mass) 

d = m/V = MP/RT 

Mixtures of Gases: 

Partial Pressures 

∙ Partial Pressure:  

The pressure a gas in a mixture would exert on an equal volume at the same  temperature

o Pi = niRT/V

∙ Daltons Law of Partial Pressures:

∙ P = ∑Pi

Behavior of Gasses: 

Effusion: 

Effusion describes the escape of a gas molecule from a sealed container Graham’s Law of Effusion:  

Diffusion: 

Diffusion describes the spread of gas molecules through other gas molecules

Kinetic vs. Potential Energy  

Kinetic Energy: 

∙ K = 1/2mv2 

o m = mass

v = velocity

Ex:  

1. A thrown ball

2. A car rolling downhill

3. Molecules in constant random motion

Potential Energy

Chem 1515 Midterm 2 “Study Guide”

∙ An object at a height (U = mgh)  

o m = mass, g = constant, h = height

∙ Two charged objects (U = k*Q1*Q2/d)

o k = constant, Q1, Q2 = charges, d = distance

Potential Energy can be converted to Kinetic Energy

Units of Energy: 

Joule (J)  

The amount of energy required to move an object that weighs 1N a distance of one  meter

∙ J = N m = kg m2 / s2 

Calorie (cal)

The amount of energy required to raise the temperature of 1g of water 1֯C

∙ 1 cal = 4.184 J 

∙ 1 Cal = 1 kcal 

Internal Energy  

Internal Energy is the total amount of energy of all forms in the system.

∙ E = K + U 

∙ ∆E = E(final) – E(initial) 

Heat vs Temperature 

Heat and temperature are not the same!

∙ Temperature is a measure of the average velocity of the atoms and  molecules in an object.

∙ Heat is a measure of the total amount of energy contained in the motions of  atoms and molecules in an object

Energy Transfers  

The change in internal energy through any process is equal to the sum of work and  heat being transferred to or from the system

∆E = E(final) – E(initial)  

∆E = w + q 

∙ Positive changes in energy represent energy transferred into the system, or  into that type of energy

∙ Negative changes in energy represents energy transferred out of the system,  or out of that type of energy

Enthalpy

Chem 1515 Midterm 2 “Study Guide”

Since most reactions occur at constant (atmospheric) pressure we typically will be  interested in the heat transfer under such conditions  

∆H = ∆E – W(expansion) 

Heat of Fusion: 

Heat of Fusion: Amount of energy required to melt (solid ֯ liquid) or freeze (liquid ֯ solid) a given amount of a substance  

Melting a compound will require heat transfer to the system from surroundings: ∙ ∆E = q(f) n  

Freezing a compound will transfer heat from the system to the surroundings:  ∙ ∆E = -q(f) n  

Heats of Vaporization and Condensation: 

Heat of Vaporization: Amount of energy required to vaporize (liquid ֯ gas) or freeze  (gas ֯ liquid) a given amount of a substance

Vaporizing a compound will require heat transfer to the system from the  surroundings:

∆E = q(v)N 

Condensing a compound will transfer heat from the system to the surroundings: ∆E = -q(v)N 

Hess’s Law 

If a reaction can be written as the sum of two or more reactions, then the enthalpy  of reaction is the sum of the enthalpies of those reactions

Standard Molar Enthalpy of Formation  

∙ Standard Molar Enthalpy of Formation (∆H(f)O): enthalpy change that results  from forming one mole of compound from its component elements in their  standard states

∙ Standard State: The most stable form of an element at 1 bar of pressure and  a specified temperature

Chemical Fuels: 

Their reaction with atmospheric oxygen is very exothermic due to:

1. Weak bonds in fuel

2. Strong bonds in the combustion products

Chem 1515 Midterm 2 “Study Guide” 3. Fewer bonds in the reactants than in the products

Foods: Fuels for Our Bodies 

∙ Caloric value: amount of energy released (in kcal) from the combustion of one gram of a food

∙ In the body the oxidation of the fat’s carbohydrates, and proteins in food  occurs through various metabolic pathways, and not through direct  combustion

∙ Since enthalpy is a state function however we can determine the caloric  value of foods using direct combustion in a bomb calorimeter

Why foods are good biological fuels:

∙ In the combustion of fats, carbohydrates and proteins the number of bonds  formed is approximately equal to the number of bonds broken

∙ The bonds formed are mostly C-O, and O-H bonds however which are much  stronger than the C-C and C-H bonds in the reactants

Page Expired
5off
It looks like your free minutes have expired! Lucky for you we have all the content you need, just sign up here