CHEM117final

[13] What is the purpose of the standard solution?

To compare against the experimental values

[15] charge is measured in what?

coulombs (C)

[15] electrons are charged particles. the amount of charge that passes per unit time is called ____

current

[3] The pressure of a gas results from....

gas particles colliding with the container walls

[1] Vpipet avg. =

(Vpipet1 + Vpipet2+....)/5

[3] what are the temperatures that are equivalent to the value of absolute zero?

-273 C -0 K

[3] select the safe methods to determine if a hot plate is heating.

-observe the heating indicator light -place the back on your hand a few inches above the surface

[1] Density...

-varies with temperature -relates a mass to its volume -determines if a substance floats or sinks -may have units of grams per milliliter (g/mL)

[1] determine conservation of volume based on water-acetone interactions

-volume is not conserved in water-acetone interactions -water and acetone interact in such a way to reduce volume

[1] A student measures the volume of acetone delivered by a volumetric pipette several times and obtains volumes of 4.96, 4.97, 4.92, 4.93 and 4.97 mL. The average volume delivered by the pipette is 4.95 mL. What is the deviation of the last measurement? Report your answer to 2 places past the decimal point and use standard abbreviations to indicate units.

.02mL

[1] A volumetric pipette was found to deliver 4..98 mL of acetone 24°C. The mass of the acetone was measured to be 3.9791 g. What is the density (in g/mL) of acetone at 25°C? Report your answer to 4 digits past the decimal point.

0.7990

[12] What is the stoichiometry of Na2S203 to I2?

2 to 1

[1] A student measures the volume of water delivered by a 10mL volumetric pipette several times and records measurements of 9.95, 9.96, 9.91, 10.02 and 9.94 mL. What is the average of the five measurements? Report your answer to 3 significant figures and do not include units in your answer.

9.96

[15] a faraday is a constant and has a value of what?

96,485 C/mole of electrons

[15] Define Semiconductors

A semiconductor is a substance, usually a solid chemical element or compound, that can conduct electricity under some conditions but not others

[12] what is a serological pipet?

A serological pipet is calibrated to dispense a precise volume of liquid when emptied completely. It does not have a 0 mL mark and its volume units increase from bottom to top of the pipet

[10] what is a state function? Give an example

A state function is independent of the path from initial to final state. Enthalpy is a state function

[2] The plot below shows a conductometric titration where a strong acid is titrated with a strong base. Identify the features labeled on the graph.

A- conductance B- equivalence point C- volume of strong base

[5] Explain the stages of nanoparticle synthesis

A. Nucleation - the sub-nanometer sized particle grows from a few bonded atoms to the point where the atomic arrangement begins to resemble the arrangement in the final nanoparticle. B. Growth - particles grow to final size.

[5] Define Beer's Law?

A= ebc

[12] What does the addition of a catalyst to a reaction result in? Does this speed or slow the reaction?

Addition of the catalyst lowers the activation energy, or barrier. It speeds up the reaction

[9] what are alkanes? alcohols? which has stronger intermolecular forces? why?

Alkanes are hydrocarbons. Alcohols have a carbon atom bonded to an -OH group. Alcohols have stronger intermolecular forces because of hydrogen bonding.

[12] Define reducing agent

Appears as its oxidized form in the products.

[12] Define oxidizing agent

Appears as its reduced form as a product.

[2] what is the acid-base reaction done in Experiment 2?

Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2H2O(l)

[15] Define insulators

Bad conductors of electricity

[15] Define Polymer

Class of macromolecules with structures built up by repetitive bonding of many smaller molecules called monomers

[15] What is the relationship between temperature and conductivity?

Conductivity decreases as temperature increases

[7] define polyatomic ions. Give a few examples.

Covalently bonded atoms in which there is an overall charge. ex. SO4-2, CO3-2, and OH-

[5] Define the term nano.

Denotes a factor of 10-9

[9] Dipole-dipole? Disperson? Hydrogen bonding?

Dipole-dipole- exists between polar molecules Dispersion- "London forces or Van der Waals", temporary dipoles that form between nonpolar molecules Hydrogen- occurs when a hydrogen atom that is bonded to O,N, or F is attracted to the O,N, or F atom of another nearby molecule STRENGTHS: Hydrogen> Dipole-Dipole > London forces

[9] define london dispersion forces, dipol-dipole forces, and hydrogen bonding. Give an example of each

Dispersion - weakest intermolecular force. Result from asymmetrical distribution of electron density around an atom or molecule that results from the short lived fluctuations in the distribution of electrons in a molecule. Ex. CH4. Dipole-dipole - result from alignment of asymmetrical charge distributions between molecules. Ex. HCl. Hydrogen bonding - not a "real" bond but formed when a hydrogen approaches an electronegative atom in an adjacent molecule. Ex. H2O

[2] Classify each of the following as an electrolyte or a nonelectrolyte -a soluble ionic compound -table sugar -CH3OH -NaCl -KI -a substance that forms an aqueous solution that does not conduct electricity -NaOH -most molecular solutes

ELECTROLYTE -a soluble ionic compound -NaCl -KI -NaOH NONELECTROLYTE -most molecular solutes -table sugar -CH3OH -a substance that forms an aqueous solution that does not conduct electricity

[10] classify the following phase changes as endothermic or exothermic -gas to liquid -liquid to gas -solid to liquid -gas to solid -solid to gas -liquid to solid

ENDOTHERMIC -solid to liquid -liquid to gas -solid to gas EXOTHERMIC -gas to liquid -liquid to solid -gas to solid

[2] define weak and strong electrolytes? provide examples of both

Electrolytes- dissociate in solution to form ions that allow the solution to conduct electricity Weak Electrolyte- dissociates poorly in solution (ex. CH3COOH and tap H2O) Strong Electrolyte- dissociates completely (ex. NaCl, CaCl2, HCl)

[7] define electronegativity. what element is the most electronegative?

Electronegativity- the relative tendency of an atom to attract electrons to itself when chemically combined with another atom. Fluorine is the most electronegative element

[12] What biological molecule catalyzes reactions in humans?

Enzymes

[1] TRUE/FALSE Because acetone is a common chemical, it is okay to work in lab without wearing safety goggles if you are only handling acetone

FALSE

[7] For each of the following atoms, select the number of electrons the atom needs to gain or lose to be consistent with the octet rule. -Galium (Ga) -Tellurim (Te) -Iodine (I) -Rubidium (Rb)

Ga- lose 3 electrons Te- gain 2 electrons I- gain 1 electron Rb- lose 1 electron

[7] Rank these bonds from most ionic to most covalent in character. K-F F-F Cl-F Br-F Ca-F

MOST IONIC K-F Ca-F Br-F Cl-F F-F MOST COVALENT

[9} which of the following exhibit only London (dispersion) forces? -H2O -He -Cl2 -HCl

He and Cl2

[10] The reaction done in Exp. 10 is an application of ____'s Law?

Hess's

[15] Define Homopolymer and Copolymer

Homopolymers - one type of monomer Copolymer - two or more monomer units

[9] which type of molecular interactions determine a molecules melting range?

Hydrogen bonding, Dipole-dipole, Van der Waals

[13] Define equilibrium constant

Indicates whether the equilibrium is reactant or product favored

[2] What are acid-base indicators? Name 2.

Indicators- chemicals that change color in the presence of acids or bases ex. Litmus, in Litmus paper, is pH sensitive to the presence of acid or base in the reaction ex. Phenolphthalein

[7] Rank the elements below according to electronegativity -F,Cs, Ga, K, N

MOST ELECTRONEGATIVE -F -N -Ga -K -Cs LEAST ELECTRONEGATIVE

[15] what is conductivity?

Measure of the ability of that substance to conduct electricity.

[9] which liquid had a larger vapor pressure at room temperature? Methanol or ethanol? Why?

Methanol has the higher vapor pressure. Methanol (H3C-OH) is quite polar with H-bonding, as is Ethanol (CH3CH2-OH). What sets the two apart is the fact that ethanol has a greater molecular surface area for London-dispersion forces.

[12] what is activation energy?

Minimum energy needed for molecules to collide.

[1] Vpipet =

Mwater / Dwater

[5] what is the complexing agent used in this experiment?

NaBr

[5] identify the power of 10 that defines each of these prefixes: -nano -kilo -micro -milli -mega

Nano = 10^-9 Kilo= 10^3 Centi= 10^-2 Micro= 10^-6 Milli- 10^-3 Mega- 10^6

[2] Is H2SO4 a flammable substance?

No

[9] what should you do in case of fire?

Notify the lab instructor, evaluate the situation, move away from the fire

[10] Classify each of the following as a path function or a state function. -energy -heat -work -distance traveled -enthalpy

PATH FUNCTION -heat, work, distance traveled STATE FUNCTION -energy -enthalpy

[15] What is the organic polymer made in Exp. 15?

Polypyrrole

[5] Experiment 5?

Preparation and Optical Properties of Silver Nanoparticles

[12] What is the rate of A + B → C?

Rate = k[A]^m[B]^n

[2] define acid-base reactions?

Reaction of an Arrhenius acid (H+) with an Arrhenius base (OH-) that results in neutralization to produce water (H2O)

[15] 8. Electrochemical reactions that involve the transfer of electrons between reacting species are called __________.

Redox reactions

[15] what is n?

Represents the number of pyrrole molecules in the polymer.

[15] Was the polymer a conductor or semiconductor? Why?

Semiconductor. As conductivity increased, so did temperature

[15] what anion was used in this experiment?

Sodium dodecylbenzene sulfonate

[1] TRUE/FALSE Conservation laws originated as experimental observations

TRUE

[9] True/False vapor pressure dependent on temperature?

TRUE

[10] How do you find ΔT?

Tf - Ti

[5] what happens at the oxidation step?

The etching agent reoxidizes the metal on less stable surfaces of the metal ion in order to ensure the most stable shape and size of nanoparticles.

[10] define enthalpy change

The heat flow per mole compound.

[5] lambda max?

The lambda max of a compound is the wavelength at which the species exhibits the largest absorbance. This appears as the highest peak on the absorbance spectrum.

[12] what are m and n?

The orders of the reaction with respect to each reactant.

[13] Define Le Chatelier's principle

The principle that if any change is imposed on a system that is in equilibrium then the system tends to adjust to a new equilibrium counteracting the change

[12] what is k?

The rate constant for the reaction

[10] Define the first law of thermodynamics

The total energy of the universe is a constant and cannot be created nor destroyed, merely converted into another form.

[1] Deviation =

Vpipet - Vpipet avg.

[15] what factors affect polymer properties?

chain length, intermolecular forces, and the extent of chain branching

[7] define a covalent bond. What is the difference between a polar and nonpolar covalent bond? (give examples of each)

a COVALENT BOND is formed when 2 atoms share a pair of valence electrons. When sharing is equal there is a NONPOLAR bond. Diatomic molecular are nonpolar and covalent bonds. When there is no sharing you get a POLAR bond. ex. CO2, CF4, H2O

[5] define the term nano

a factor of 10^-9

[15] define polymer

a large molecule made of repeating subunits

[15] define monomer

a repeating subunit used to make a polymer

[7] define a dipole

a separation in charge along a bond

[2] what is Phenolphthalein?

a single, pure compound that adopts 2 different structures in acidic and basic solution

[2] define precipitate?

a solid formed when 2 liquids are mixed

[2] what is the acid in the reaction of Ba(OH)2(aq) + H2SO4(aq) → BaSO4(s) + 2H2O(l) what is the base? precipitate?

acid: H2SO4 base: Ba(OH)2 precipitate: BaSO4

[12] Which of the following factors will influence the rate of a chemical reaction? Select all that apply.

adding a catalyst, changing the concentration of reactants, and changing the temperature

[9] In the chemicals used in experiment 9, which had H-bonding? which had no H-bonding?

all the alcohols had H-bonding

[15] current is measured in what?

amperes (A)

[3] define empirical laws?

an equation that described the relationship of a particular set of variables that is not based on a real model of behavior

[7] what is an expanded valence? name on element that has an expanded valence

an expanded valence is when an element can exceed 8 or more electrons. Phosphorus is an example

[3] explain the pressure-temperature relationship using the concepts of molecular velocity and molecular collisions.

as the temperature of a substance increases, the velocity increases. As a result, the energy and # of molecular collisions will increase and this will cause pressure to increase. The opposite will occur when pressure decreases

[9] what happens to vapor pressure at higher temperatures?

at higher temperatures, kinetic energy increases, which increases the percentage of molecules with sufficient energy to overcome intermolecular attractions and exist in the vapor state

[15] in electroplating, the object to be plated is which part of an electrolytic cell? what is electroplating?

cathode electroplating is the deposition of a thin layer of a metal on an object through the process of electrolysis

[5] what is the region of visible light?

between 400 and 700nm

[7] what is molecular shape derived from?

bond lengths and geometry of the central atom(s)

[5] Please select the reasons why you do not discard broken glassware in regular garbage or recycling containers. (Select all correct responses)

broken glass could still contain chemicals that need to be disposed of properly; potential injuries could occur if staff do not see the broken glass

[7] define VSPER theory

can be used to describe the 3D structure around the central atom in a Lewis dot structure

[3] define the relationship between pressure and temperature

directly proportional

[9] what is the dominant intermolecular force of attraction between C5H12 molecules

dispersion forces

[2] define nonelectrolyte? give examples

does NOT dissociate in solution and therefore does not conduct electricity (ex. Ch3OH and distilled H2O)

[15] a voltmeter is primarily used to measure _______

electrical potential

[12] when using a serological pipet, the correct volume is dispensed by....

emptying the contents of the pipet completely into the desired container

[1] define callibration

experimental parameters used to relate to relate to fundamental quantities

[3] define pressure?

force per unit area Units = atm, kpa, lb/in.2

[7] define an ionic bond

formed when valence electrons are transferred from one atom to another, effectively creating a cation and anion

[2] which of the following would be the best choice for dealing with a base spill in lab?

have the instructor or TA clean it up

[10] what is q?

heat and not a state function

[9] For liquids, which of the following factors affect vapor pressure? Check all that apply.

intermolecular forces, temperature

[3] determine the relationship between pressure and volume

inversely proportional

[15] What is the relationship between conductivity and resistivity?

inversely related

[5] what is the role of sodium borohydride?

it is the reducing agent

[3] define Boyle's law mathematically

k = PV

[3] define k

k = the constant ratio, also called the proportionality constant

[7] what are non-bonding electrons called?

lone pair electrons

[1] determine conservation of mass based on water-water and water-acetone interactions

mass is conserved in water-water and water-acetone interaction

[7] the interactions between molecules is dictate by what?

molecular shape

[7] define DNA intercalation (binding in the ladder)

molecules that can squeeze between the steps of the DNA ladder and are flat

[5] Solutions made of the same type of nanoparticle can be very different colors. What property determines the color of a nanoparticle solution?

nanoparticle diameter

[9] define intermolecular forces

noncovalent interactions between molecules

[7] define valence electrons

outermost "s" and "p" electrons

[5] define the term reducing agent

oxidizes metal ions to form metal nanoparticles M+(aq) + e- →M0(s)

[2] indicate the color of phenolphthalein within the pH ranges listed below: pH < 8.3 8.3 < pH < 10 pH > 10

pH < 8.3-- colorless 8.3 < pH < 10-- faintly pink pH > 10-- bright fuchsia

[9] what are the partial charges on H2O?

partial positive on H, partial negatives on O

[1] What can be done to ensure that your measurements are reproducible?

perform multiple trials

[15] the driving force for the electrons is measured by______

potential

[5] what is molar absorptivity?

property of the solute, known as E

[5] what 3 factors that most significantly influence the properties of nanoscale materials.

quantum mechanical effects, size, and shape

[12] What is described by chemical kinetics?

rate of a chemical

[5] if red light is absorbed, what color(s) are being obesrved?

red light reflects blue and yellow light, which makes them appear green

[1] define control experiment?

show whether or not a result is due to the experimental factor no taken into account

[7] define "binding in the grooves"

small molecules that can bind into the major and minor grooves of DNA. Typiucally crescent-shaped

[5] what happens at the reducing step?

sodium borohydride reduces the silver

[13] What does a double arrow symbol indicate?

that a reaction can proceed in either direction

[10] what is the purpose of the coffee cup in a coffee cup calorimetry experiment?

the coffee cup insulates the experiment, minimizing heat loss to the environment

[9] A chemist has three compounds of similar molecular weight, but with different dominant intermolecular forces. Select the compound that should have the lowest boiling point, based on the compound's dominant intermolecular force.

the compound in which dispersion forces are dominant

[3] how well data fits a linear regression can be judged by _________

the correlation constant R^2; the closer R^2 is to 1, the better the linear fit

[2] define equivalence point

the equivalence point is the point at which stoichiometrically equal amounts of the reactants have been combine

[3] The temperature of a gas is a measure of....

the kinetic energy of the gas particles

[12] define activation energy

the minimum kinetic energy that particles must possess for a chemical reaction to occur

[2] what best explains why electrolyte solutions conduct electricity?

the presence of free-flowing ions

[3] for a fixed volume of gas at a fixed temperature, what will happen if the amount (# of moles) is doubled?

the pressure exerted by the gas will double

[5] define transmittance

the ratio of light intensity I that passes through the solution to the light intensity that passes through a blank sample, Io

[2] When preparing a buret for use in lab, the buret must always be cleaned thoroughly. Prior to being filled with solution, the buret is rinsed one last time. What is the buret rinsed with, and why?

the solution that is being titrated to ensure that when added to the buret, it will not be diluted with excess water

[9] define polarizability

used to describe the extent to which an external electric field can distort the charge of distribution in a molecule

[15] potential is measured in what?

volts (V)

[1] Density is defined as the ratio of mass to ____?

volume

[10] What is the difference between ΔH and ΔH◦?

ΔH◦ is molar enthalpy