suffering!

Entropy

(S), for dilute solutions colligative properties are due to this

ppt=

(g NaCl/ g bay water) * 1000

-qreaction=

(mC∆T)water+Ccal∆T

-(mC∆T)hotwater=

(mc∆T)cold water + CcalT

Buffering region is usually within

+/- 1 pH unit from the pKa

How to find pKa when given Ka

-log(ka)

ΔS(sys)=

-ΔS(surr)

Correctly rounded, 2.7 x 10-3 cm - 3.8 x 10-4 cm is

0.0023

If the transmittance of a particular sample was measured to be 50% at a certain wavelength, (i.e. %T=50) what would the absorbance be?

0.30

What is the concentration in ppt of a solution made by dissolving 10 mg NaCl into 25 mL of water? Assume the density of water is 1 g/mL.

0.4 ppt

You run a chromatogram of a metal ion. The metal ion travels 8.86 cm. What is the Rf of the ion if the solvent traveled 17.15 cm? Report your answer to two digits past the decimal place.

0.52

A calibration curve for compound X was constructed by measuring the absorbance of a series of standard solutions at a fixed wavelength and yielded the following equation: A = (0.5 M^-1)*[X] If the percent transmittance of an unknown solution was measured to be 50%, then what is the molar concentration?

0.6

For the reaction, A=> B=> C, the time dependence of [A] was found to be, [A]t = (10 M)*exp[(-5s^-1)*t]. What is [A] after 500 ms?

0.8 M

A calibration curve for compound X was constructed by measuring the absorbance of a series of standard solutions and yielded the following equation: A = (0.5 M^-1)*[X] If the path length was 5 mm, then what is the absorptivity (ε) in units of M^-1cm^-1?

1

Which of the following is associated with an increase in entropy? I. Solute molecules diffusing in solution. II. Water evaporating. III. Water freezing.

1 and 2

What is the molality (mol/kg) of a solution made by dissolving 18 grams of sucrose (C12H22O11) in 50 mL of water? Assume the density of water is 1 g/mL.

1 mol/kg

Two steps in calorimeter lab

1- calorimeter constant was determined 2- heat flow determined for the reaction by added NaOH to HCl

Calibrating SpectroVis Plus

1. From Experiment menu, choose Calibrate > Spectrophotometer. Let it warm up. 2. Place the blank cuvette in Spectrophotometer. Be sure there are no fingerprints & make sure it is aligned with clear side.

Spectrophotometry Post Lab

1. Open data in excel. 2. add the point Conc.=0 and A=0.00 3. Plot A vs conc. Add linear trend line, set intercept at 0. Display equation and R-squared.

Obtaining an absorption spectra

1. Place sample in slot. Click COLLECT. Spectra will appear. Click STOP. 2. For λmax, click CONFIGURE SPECTROMETER, choose absorbance vs concentration, select desired range.

Titrations

1. Rinse buret with NaOH/any titrant. Set up experiment. Fill buret with titrant. Put the solution you're titrating in a beaker. Add drops of indicator to it. 2. Record starting volume of titrant in buret. 3. Launch LoggerPro. Place probe in beaker & record initial pH. 4. Click COLLECT. Add titrant in small 0.2-0.5 mL increments. Swirl beaker and click KEEP with each addition. 5. Enter new buret reading in box that appears. When color flashes, start adding titrant dropwise until the solution completely changes color. This is the endpoint. 6. Continue to add titrant in 0.2-0.5 mL increments until pH is of excess (i.e. 11). Click STOP. 7. Make grap using Excel.

Successive dilution method (w/ chlorophyll)

1. in a 10 mL volumetric flask, place 5 mL of stock solution and fill the rest with distilled water. 2. in the second diluted solution, there should be 5mL of the first diluted solution and 5 mL of water. 3. Concentrations will be 50%, 25%, etc

Calibration Curve Development

1. put sample in slot. Click KEEP. enter concentration. 2. put second most concentrated sample. click KEEP enter concentration. 3. Repeat as needed. Click STOP.

Research project procedures

1. synthesize zeolites 2. rinse & fill cuvette with dye 3. make successive diluted solutions & fill cuvettes with solutions 4. calibrate & blank spectrophotometer with water 5. create absorption spectrum using stock solution 6. record λmax & absorbance 7. Absorption vs Concentration, find absorbance values@ λmax 8. place each of the 3 variables into centrifuge tube 9. insert 10 mL of stock solution into each tube 10. centrifuge then put liquid into cuvettes 11. loggerpro reopened & recalibrated 12. collect full spectrum & absorbance at λmax for each sample cuvette

The absorptivity (ε) of a particular chemical is 4.6 (L/Mol*cm) . What is the concentration (M) of a solution made from this chemical if a 0.9 cm sample has an absorbance of 4.64? Report your answer to two digits past the decimal point. Do not use scientific notation. Do not include units with your answer.

1.12 +- 0.01

The concentration of sodium chloride in your water sample can be calculated using the following equation: VAgNO3MAgNO3 = VNaClMNaCl. 11.63 mL of AgNO3 is required to titrate 9.31 mL of a bay water sample. What is the molar concentration of NaCl in the bay water sample if the AgNO3 solution is 0.96 M? Report your answer to two places past the decimal point.

1.20M

A solution was made by dissolving 0.025 grams of sodium benzoate in 191.0 mL of 0.264 M benzoic acid. Assuming the change in volume when the sodium benzoate is added is not significant, use the Henderson-Hasselbalch equation to estimate the pH of the solution. The Ka for benzoic acid is 6.3 x 10-5 and the molar mass of sodium benzoate is 144.11 g/mol. Report your answer to 2 digits past the decimal point.

1.74 +- 0.01

What is log(79)?

1.90

How many d electrons in Zn2+, Cu-1, Co+3, Mn+7, Ti+4, Ni +2

10,10,6,0,0,8

A solution was made by dissolving 2.30 grams of ammonium chloride in 26.00 mL of 0.10 M ammonia. Assuming the change in volume when the ammonium chloride is added is not significant, use the Henderson-Hasselbalch equation to estimate the pH of the solution. The Ka for ammonium chloride is 5.6 x 10^-10 and its molar mass is 53.49 g/mol. Report your answer to 2 places past the decimal point

10.47

The blank sample is used to set the spectrophotometer to which of the following?

100 % Transmittance

Correctly rounded, 18.0742 + 0.25 g =

18.32

Consider the following redox reaction: 2 Fe3+(aq) + Zn (s) => 2 Fe2+ (aq) + Zn2+ (aq) How many electrons are transferred per atom of zinc?

2

For the following reaction, k_1 A<=>B k_-1 if k1=2k_-1, what is K?

2

Which object in the schematic diagram of a spectrophotometer allows for a single wavelength of light to be selected?

2

Report the following number to three significant figures: 2.04502 (Do not use scientific notation.)

2.05

Determine the volume (mL) of stock solution required to make 45 mL of a 6 mM solution starting with a 0.1 M stock solution. Report your answer to two digits past the decimal point. Do not use scientific notation. Do not include units with your answer.

2.7 +- .01

Determine the volume of stock solution required to make 26 mL of a 15 mM solution starting with a 0.14 M stock solution. Report your answer to two significant figures.

2.8E0 (2.8 × 100) mL

The concentration of sodium chloride in your water sample can be calculated using the following equation: VAgNO3MAgNO3 = VNaClMNaCl. If 20.37 mL of 1.55 M AgNO3 is required to titrate 10.66 mL of an undiluted bay water sample, what is the molar concentration of NaCl in the bay water sample? Report your answer to two digits past the decimal point. Do not use scientific notation. Do not include units with your answer.

2.96 +- 0.01

Rounded correctly, 2.000 cm × 10.0 cm =

20.0 cm^2

According to the lab manual, what is the vapor pressure of water at 298 K?

23.76 Torr

A student measures the temperature of water in a beaker to be 25.5 °C. A conversion table lists the value of absolute zero as -273.15 °C. Reported to the correct number of significant figures, what is the temperature of the water on the Kelvin scale?

298.6

Half Reaction for the SHE

2H+ + 2e- --> H2

How many significant figures are in the number 12.5? Give a numerical answer.

3

How many trials of this experiment (7) will you perform?

4

A solution with a concentration of 2.08 M is measured to have an absorbance of 0.72. A second solution of the same chemical is measured under the same conditions and has an absorbance of 1.59. What is the concentration of the second solution? Report your answer to two numbers past the decimal point.

4.59M

A calibration curve for compound X was constructed by measuring the absorbance of a series of standard solutions and yielded the following equation: A = (0.5 M-1)*[X] If the path length was 1 mm, then what is the absorptivity (ε) in units of M-1cm-1?

5

For the reaction, k_a HBB + H2O <=> H3O+ + BB- the equilibrium constant, Ka, 2.0 x 10^-5, the ratio of [BB-] to [HBB] is 2.0, what is the pH of the reaction solution?

5.0

Butane has the molecular formula C4H10. Assuming carbon has a mass of 12 and hydrogen has a mass of 1, what is the approximate molar mass of butane?

58

What is the volume of stock solution of 51 g/L AgNO3 required to make a 50 mL solution of 0.03 M final concentration?

5mL

If you follow the directions in the procedure exactly, how many times will you weigh the butane lighter?

6

The Ka of carbonic acid is 4.3 x 10-7. What is the pKa?

6.4

The number of significant figures in 0.0009753100 is

7

7.523 mL of bromine is transferred to a graduated cylinder with scale marks 0.1 mL apart. Which of the following will be the correct reading taken from the graduated cylinder?

7.52 mL

You run a chromatogram of a metal ion. The metal ion has an Rf of 0.53 What is the distance the spot traveled if the solvent traveled 15.0 cm? Report your answer to two significant figures.

8.0E0 (8.0 × 100) cm

reaction scheme

A -- k1 --> B -- k2 --> C

During this experiment you will measure the volume of which of the following using water displacement?

A gas

packed column

A hollow tube that is filled with particles coated with stationary phase material

Which of the following will not be used in today's experiment?

A thermometer a temperature probe and a ring stand

Beers Law

A= ebc

Beer's law

A= ebc A= absorbance e= molar absorptivity (constant) b= distance light travelled c= sample concentration

Acids change litmus paper from ___ to ___

Acids change litmus paper from BLUE to Red

net ionic equation

Ag+ (aq) + Cl- (aq) -> AgCl (s)

NaCl (aq) + AgNO3 (aq) ->

AgCl(s) + NaNO3 (aq)

How many significant figures are in the number 3,100?

At least 2

weak base with strong acid

B + H3O+ -> BH+ + H2O

Use the standard reduction potentials for the reactions shown below to determine which species is the best oxidizing agent. Br2 (l) + 2 e- → 2 Br- (aq) E° = +1.07 V Cr3+ (aq) + 3 e- → Cr (s) E° = - 0.74 V I2 (s) + 2 e- → 2 I- (aq) E° = +0.54 V

Br_2 (l)

n (moles)=

C*V concentration * volume

dissociation of carbonic acid

CO2 + 2H2O <---> H3O+ + HCO3-

formation of carbonic acid

CO2 + H2O <--> H2CO3

Bentonite clay contains all of the following elements except:

Carbon It contains: Al, K, Si

qcal=

Ccal∆T

You run a chromatogram of a mixture of two metal ions. The spot for one metal ion (compound X) has an Rf of 0.450; the spot for the other ion (compound Y) has an Rf of 0.600. Which compound travels a greater distance along the chromatogram?

Compound Y

The absorptivity constant is independent of which of the following?

Concentration of the solute

In experiment what was the cathode?

Cu (Copper)

Five transition metals we identified in chromatography lab

Cu2+, Ni2+, Fe3+, Co2+, Zn2+

What can we use in math equations for standardization?

Dilution (M1V1=M2V2)

E(cell)=

E(cathode) - E(anode)

E cell equation

Ecell= Ecath- Ean

Use the standard reduction potentials for tin and silver to calculate E°cell for the oxidation-reduction reaction: Sn2+ (aq) + 2 Ag (s) → 2 Ag+(aq) + Sn (s). Sn2+ (aq) + 2 e- → Sn (s) E° = - 0.14 V Ag+ (aq) + e- → Ag (s) E° = +0.80 V

Equals -0.94V (100%)

The standard reduction potential for the reaction, Au3+(aq) + 3 e- → Au (s), is +1.50 V. What is the standard potential for the reverse reaction, Au (s) → Au3+(aq) + 3 e- ? Include a sign and use standard abbreviations to indicate units in your answer. Do not add any spaces.

Equals -1.50V (100%)

A BLANK sample is used to set the spectrophotometer to 0% Transmittance.

False

A reaction reaches the steady state when all of the reactants have been converted to products.

False

All solid chemical waste can be put into the trash can.

False

As ice melts to form water, the amount of entropy decreases.

False

Because lab data is collected in pairs, it is okay for lab partners to turn in a single data reduction and analysis report for each experiment.

False

Bentonite clay sequesters PAH's by the formation of permanent covalent bonds.

False

CN- ligands produce large Δ while I- produce small Δ; therefore, CN- is a weak field ligand and I- is a strong filed ligand.

False

Chemicals will be used in this modeling experiment and therefore goggles need to be worn

False

Consider the reaction A + 2 B in an equilibrium reaction with 3 C + D. at equilibrium, if during 1 minute 5 moles of A is formed by the reverse reaction, then 5 moles of C and 5 moles of D are formed by the forward reaction.

False

Consider the reaction at equilibrium; if during 1 minute 10 moles of C is formed by the forward reaction, then 5 moles of A and 5 moles of B are formed by the reverse reaction.

False

Dextrin is added to the titration solution to prevent the Ag+ ions from being reduced to Ag (s).

False

Dichlorofluoresceinate is used in this experiment as a redox indicator

False

Ferric, fluoride, and ferrous salts are used to prepare the magnetic clay.

False

For reactions with small equilibrium constants, the forward reaction will have a much larger rate constant than the reverse reaction.

False

Hydrocarbon, H2O, and O2 emissions result from incomplete combustion from automobiles

False

I do not have to report burns from hot glassware to my instructor.

False

If you dissolve 1.5 moles NaCl into 2.00 kg of a 0.50 moles/kg solution of NaCl, the molality of Na+ is 1.125 moles/kg.

False

In Kinetics II experiment, each roll of the dice represents one chemical reaction occurring

False

In Kinetics II experiment, you will model a 1 step chemical reaction using different reaction rates.

False

In the colligative properties experiment, you will learn the second and third laws of thermodynamics.

False

In this experiment, the acidic salt potassium hydrogen phthalate (KHP) is used to determine the concentration of primary standards such as hydrochloric acid

False

In this experiment, you will explore the relationship between the oxidation state of a metal and the color of a transition metal complex.

False

Inorganic compounds depress the freezing point of water while organic compounds elevate the freezing point.

False

It is acceptable to remove goggles in lab to wipe them down when they fog up.

False

It is dangerous to place hot glassware on a piece of thin wire mesh.

False

It is okay to mix a bunch of chemicals together, even though it's not a part of the lab procedure, since I know nothing will happen anyway.

False

It is safe for my lab partner to look directly into the open end of a test tube.

False

Ligands such as I- produce small Δ, they are known as strong field ligands

False

Metal cations become easier to reduce as the reduction potential becomes more negative.

False

One of the fundamental ideas of chemical equilibrium is that equilibrium can be established from the forward direction only.

False

PAH are common, harmless chemicals found in air and municipal water sources.

False

Potassium hydrogen phthalate (KHP) can be used to determine the concentration of acid solutions.

False

The buffer that controls the pH of ocean water is predominantly composed of a mixture of HCO3- and H2CO3

False

The color of permanganate, MnO4-, represents the excitation of electrons from lower energy d orbitals into empty or half-filled higher energy d orbitals.

False

The conjugate acid of SO4^2- is H2SO4.

False

The experimental work for this lab does not involve any chemical reactions therefore safety attire does not have to be worn.

False

The freezing point of salt water is higher than that of pure water.

False

The ideas and concepts developed through federally funded research programs belong to the institution that publishes the results of the work.

False

The objective of Experiment14 (Determination of EquilibriumConstant, Ka, and pKa) is to find out why bromothymol blue has an intense blue color when the pH of its aqueous solution is high.

False

The pH of a buffered solution changes very little even when large amounts of strong acid or strong base are added.

False

The purpose of the equilibrium experiment (14) is to determine the rate constant of a reaction.

False

The purpose of this experiment is to find the best compound to use for coolant.

False

The rate constant, k, describes the rate of the reaction; the smaller the rate constant is the faster the reaction.

False

The rate-determining step of a chemical reaction has the largest rate constant of all the steps in the reaction.

False

The value of the equilibrium constant for a particular reaction is independent of temperature.

False

The wavelength of maximum transmittance is designated as lmax (lambda max) and is characteristic of the material absorbing the light.

False

The wavelength of maximum transmittance is designated as λmax (lambda max) and is characteristic of the material absorbing the light.

False

To test the amount of red dye in an aqueous solution, you should measure the amount of red light (620-750 nm) that the solution absorbs.

False

When measuring the percent transmittance of red dye solutions, one should use acetone as the 100% blank.

False

Δ represents the energy absorbed when an electron moves from a high energy state to a lower energy state.

False

The rate constant, k, describes the rate of the reaction; the smaller the rate constant is the faster the reaction.

False the LARGER the K, the faster the reaction

Non-electrolytes such as sodium chloride are solutes that dissociate or ionize when dissolved in water.

False, Electrolytes completely dissociate in water

Molality is the mass of solute per liter of solution.

False, Molality = Moles solute /kg solvent

After collecting the gas sample, the pressure inside the graduated cylinder is equal to the vapor pressure of water at the temperature of the room.

False, P(dry) = P(collected) - P(H2O)

A Spec 20 spectrometer measures the amount of visible light absorbed by a colored solution. This can only be measured as % Transmittance.

False, also as Absorbance

The reason silver nitrate solution is usually stored in a dark colored bottle is that it is air-senstive.

False, it is LIGHT sensitive, it will decompose in the action of light

Dichlorofluorecein is an inorganic acid with 2 chlorine atoms and one fluorine atom.

False, it is organic

Because lab data is collected in pairs, it is okay for lab partners to turn in a single data reduction and analysis report for each experiment.

False, it is still single student work

Because all of the waste generated during this experiment (8) contains water, the waste can safely be disposed of by pouring it down the drain.

False, it's still containing chemicals also

If you measure the freezing points of water, a 0.1M solution of NaCl in water and a 0.1M solution of glucose in water, the NaCl solution and the glucose solution will have the same freezing point which will be lower than 0 °C.

False, salt water has a lower freezing point than pure water, and the more you add to it, the more the Fp Vary from onen another

A buffer solution is a mixture of a strong acid with its conjugate base or a strong base with its conjugate acid.

False, weak acid/base and its conjugate

Chemicals will be used in this modeling experiment and therefore goggles need to be worn.

False, working with dice, no goggles needed

What is the proper way to deal with a corrosive chemical spill on your skin?

Flush the affected area with large amounts of water for 15 minutes

carbonic acid in equilibrium w bicarbonate

H2CO3 + H2O <---> H3O+ + HCO3- blood is buffered by this

HA + H2O <-->

H3O+ + A-

weak acid with strong base

HA + OH- -> A- + H2O

bicarbonate in equilibriu q carbonate anion

HCO3- + H2O <--> H3O+ + CO3 2- ocean waters primarily buffered by this

What was added to buffer?

HCl

Identify all of the combinations shown below that are not buffer solutions. Assume all components are present in 0.10 M concentrations.

HClO4 and NaClO4 , HCl and KCl

Use the standard reduction potentials for the reactions shown below to determine which pair will result in a spontaneous reaction. I2 (s) + 2 e- → 2 I- (aq) E° = +0.54 V Fe2+ (aq) + 2 e- → Fe (s) E° = - 0.45 V Sn2+ (aq) + 2 e- → Sn (s) E° = - 0.14 V

I_2 + Fe^2+

Which of the following statements regarding this experiment, (Electrochemistry I) is TRUE?

In this experiment, you will use a piece of string soaked in potassium nitrate as your salt bridge. As part of this experiment, you will use the calculated reduction potentials to identify which solutions are zinc, magnesium, iron and tin. In this experiment, you will calculate the relative reduction potential of a solution. In this experiment, you will measure the reduction potential for solutions of Zn2+, Mg2+, Fe2+, and Sn2+.

The percent transmittance of a solution of Procion Red is measured. If adding bentonite clay were to sequester dye molecules from solution, then upon removal of the clay the measured percent transmittance should .

Increase

If the ratio of acid to base in a buffer increases by a factor of 10, what happens to the pH of the buffer?

It decreases by 1

Why did we use isopropyl alcohol in spec. lab?

It is a good, organic, relatively non polar solvent compared to water, to extract organic (relatively non polar) pigments

equilibrium constant

K

ΔT(f)=

K(f)*m K(f) solvent-specific constant m molality (moles solute/kg solvent)

Ka equation for equilibrium exp

Ka= [H3O+] + Agreen/Ablue-Agreen

Green solution Ka

Ka= [H3O+] + [BB-]green/[BB-]blue-[BB-]green

Acid Base Equilibrium Constant Equation for experiment

Ka= [H3O+][BB-]/[H2O][HBB]

Ka has many equations.. here are a few

Ka= k(f)/k(r) = [H3O+][BB-]/[HBB] Ka= [H3O+] * ([BB-]/[HBB]) Ka= [H3O+] * (f[BB-]/f[HBB]) Ka= [H3O+] * (f[BB-]/ 1- f[BB-]) f fractions

Why didn't we use acetone in spec. lab?

Lower vapor pressure and evaporates too easily for volumes to stay constant and therefore for concentrations to be accurate

In the equation for Beer's law, A = ebc, which of the following could be units for c?

M

Cations of which of the following metals will you not be working with in this experiment?

Mercury

Which section of a grant proposal depicts the strategies that will be used to achieve the goals of the research project?

Methods

Which of the following mixtures can produce an effective buffer solution?

Na2HPO4 and Na3PO4

Titration of NaCl w/ AgNO3

NaCl in beaker, AgNO3 in buret

When is it okay to drink beverages in the lab?

Never

Using a carbonate buffer system, can you keep a solution around pH 8.25? 6?

No; yes

A -k1-> B -k2-> C the time dependence of [A] was found to be, [A]t = 10*exp(-5*t) What is the value of k2?

Not enough info present

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

Perform Multiple Trials

Quniverse=

Qsystem+Qsurroundings

Which object in the schematic diagram of a spectrophotometer indicates where the sample is placed? Spectrophotometer Schematic Diagram

Rectangular Prism

Rf equation

Rf= distance traveled by spot/total distance traveled by the solvent

The purpose of adding dextrin to the titration solution is to:

Sharpen the end point of the titration

Metals used in order of reducing potential in electrochemical experiment

Sn, Fe, Zn, Mg

Which of the following best completes the following statement? The standard deviation is a way of describing the ________ in a set of data.

Spread

ΔT(f)=

T(f)solvent - T(f)solution

A colligative property is a physical property of solutions that depends on the number of dissolved solute particles in solution.

True

A reaction that is completely irreversible cannot reach chemical equilibrium.

True

A steady state is a situation in which all state variables are constant in spite of ongoing processes that strive to change them.

True

All waste containing silver should be disposed of in the appropriate waste container.

True

All waste solutions of acid and/or base should be placed in the designated waste bottles.

True

Anionic dyes such as dichlorofluoresceinate are attracted to the positively charged silver cations on the surface of the AgCl particles after the equivalence point.

True

As a precipitate forms out of a supercooled solution, the temperature of the solution will rise due to the heat evolved during crystallization.

True

As the molecular weight of a compound increases, the observed freezing point depression decreases.

True

Chemical reduction occurs at the cathode of an electrochemical cell.

True

Chemicals that can be used in this experiment include sodium chloride, sucrose, glucose and glycerol.

True

During this experiment (8), you will prepare solutions of different concentrations by perfroming dilutions of a solution with a known concentration.

True

Electrolytes such as sodium chloride are solutes that dissociate or ionize when dissolved in water.

True

Eutectic temperature is the lowest temperature at which the solution is still a liquid.

True

Even though the chemicals that we used in this experiment (14) are fairly environmental friendly, we still need to protect ourselves by wearing proper personal protection equipment (PPE) including goggles.

True

Even though the chemicals that we used in this experiment are fairly environmental friendly, we still need to protect ourselves by wearing proper personal protection equipment (PPE) including goggles.

True

Even through the acid and base solutions used in this experiment (15) are dilute, safety goggles must be worn at all times.

True

Even through the acid and base solutions used in this experiment are dilute, safety goggles must be worn at all times.

True

Every time you change the wavelength on the Spec 20, you must reset the 100% transmittance value using the "blank" sample.

True

Ferric and ferrous salts are used to prepare the magnetic clay.

True

Fingerprints on the cuvettes will interfere with transmission of light through the sample.

True

For the reaction (A-> <-B), in a reactant-favored equilibrium, the concentration of A is greater than the concentration of B and the reaction has a small equilibrium constant.

True

Funding for research is usually obtained through writing and submission of a grant proposal to a government agency. Only those proposals deemed to be the "best investments" after a review process receive funding.

True

If the reaction between bromothymol blue and water is not a single reaction, one would not be able to observe an isosbestic point in the graphical plots for the spectra in this experiment (14).

True

In Precipitation Titrations experiment, you will model the salinity profile of water in the San Antonio Bay using water samples collected in two different months.

True

In general, grant proposals are divided into three different parts: Specific aims, background and significance, and methods.

True

In this experiment (12), each roll of the dice represents the passage of one unit of time.

True

In this experiment, you will model some 2 step-reactions where each step of the reaction has different reaction rates.

True

In this experiment,(Transition Meal Chemistry and Paper Chromatography) you will identify the components of a mixture by paper chromatography.

True

In this project, you will prepare magnetic clay and test its ability to adsorb a model PAH.

True

It is a good idea to have my long hair tied back while I'm in the lab.

True

Matches and cigarette lighters should not be lit during this experiment, as the butane gas is highly flammable.

True

Molar absorptivity is a constant for a particular substance, so if the concentration of the solution is halved so is the absorbance of the solution.

True

Pigments such as chlorophyll and other colored materials (i. e., dyes) absorb energy in the visible light range (380-760 nm).

True

Prior to the equivalence point in this titration experiment, there is excess Cl- in solution.

True

The Spec 20 is an instrument that is designed to measure the amount of visible light which passes through a solution.

True

The amount of light a solution absorbs, or transmits, depends on the wavelength of the light.

True

The anionic form of bromothymol blue is blue in color.

True

The conjugate base of acetic acid (CH3CO2H) is acetate ion (CH3CO2-).

True

The equilibrium constant is a measure of the extent to which a reaction proceeds.

True

The half reaction: Ni2+ (aq) + 2 e- -> Ni (s) is a reduction

True

The ideas and concepts developed with federal grant funds belong to the universities and scientists who generate them.

True

The light that passes through a solution can be measured in terms of absorbance of a solution (the amount of light the solution absorbs) or the transmission (the amount of light that passes through a solution).

True

The measured absorbance of visible light can be used to determine the concentration of a colored material in solution.

True

The proper response to getting chemicals in your eyes is to use the eye wash station to flush the chemical out of the eyes.

True

The rate of a reaction is described by a number called a rate constant, k. However, this number can vary based on reaction conditions.

True

The rate of the reaction can be described by a number called the rate constant, k.

True

The rate-determining step of a chemical reaction has the smallest rate constant of all the steps in the reaction.

True

To decrease the volume of AgNO3 necessary to observe the end point in an argentometric titration, one should dilute the analyte solution by a factor of 2.

True

Use care when handling the silver nitrate solution as it will stain clothing and skin.

True

Use tongs to manipulate the chromatography paper once it has come in contact with the solvent.

True

Visible light consists of wavelengths ranging from 380 nm (blue/violet region) to 720 nm (red).

True

You cannot take accurate spectrophotometric measurements from a cloudy solution containing debris.

True

You should make proper adjustments for absorbance using a water blank for every wavelength you measure during this experiment.

True

What are the units of absorbance, A?

Unitless

Metal centers of transition metals

Unlike the d orbitals of a free metal cation which are degenerate, metal centers are split according to coordination geometry. way it splits depends on the metal center, the charge on the center, and identity of its ligands

Buffers Post Lab

V(eq) is highest peak in dpH/dV plot within range of equivalence oint locate V(eq) on pH vs. V plot Estimate corresponding pH determine .5V(eq) and 1.5V(eq)

g=

V*density

V1M1 =

V2M2

Which of the following statements regarding this experiment, (Electrochemistry I) is FALSE?

You will calculate the standard reduction potential for Zn2+/Zn, Mg2+/Mg, Fe2+/Fe, Sn2+/Sn and Cu2+/Cu.

Use the standard reduction potentials for the reactions shown below to determine which species is the best reducing agent. Cl2 (g) + 2 e- → 2 Cl- (aq) E° = +1.36 V Ag+(aq) + e- → Ag(s) E° = +0.80 V Zn2+ (aq) + 2 e- → Zn (s) E° = - 0.76 V

Zn

Which of the following is a component in the Henderson-Hasselbalch equation?

[Conjugate Base]

Which of the following is a component in the Henderson-Hasselbalch equation?

[Conjugate base]

The following metal complexes, [Ni(H2O)6]2+ and [Ni(NH3)6]2+, appear green and blue respectively. Which complex absorbs higher energy light?

[Ni(NH_3)_6]^2+

equivalence point

[acid]=[base]

Adsorption indicator forms

a colored layer as they adsorb onto the surface of particles in solution, the indicator is lightly negatively charged

All Buffers consist of

a conjugate acid base pair

open tubular column

a hollow capillary tube with inner walls that are coated with stationary phase material

What was used to standardize NaOH

a known weight of KHP (a weak acid)

Methods must relate ( FOR CLAY)

a physical property mathematically to concentration

Colligative Property

a physical property that depends on the number of dissolved solute particles in solution

Standard Reduction Potentials

a scale of measured standard solutions relative to the reduction potential of the standard hydrogen electrode (SHE)

Adsorption

a surface phenomena in which molecules adhere to the surface of a material, depends on the surface area and steric of the substrate

pH change of 1 is

a tenfold change in [H3o+]

Precipitation Titration

a titration that forms an insoluble precipitate, used to determine the amount of chloride in the solution

Standard curve is

absorbance vs concentration

% error

accuracy (deviation from true value)

Solutions used in chrom. exp?

acetone/Hcl solution which exchanged all the H2O with chloride ligands on the metal, treated in the ammonia chamber while it was still wet, which exchanged all the Cl- ligands with NH3 in all cases except for -OH in Fe2+ A solution of DMG was sprayed heavily, exchanging some of the metals to DMG ligands

Equivalence point

acid=base conc.

Dextrin

added to prevent coagulation of AgCl particles because increase in surface area for adsorption is important for visualization by indicator in precipitation lab

Electrons flow from

anode to cathode

oxidation occurs in the

anodic half cell

Second Law of Thermodynamics

any spontaneous change occurs with an increase of entropy of the universe

titrations using silver nitrate are

argentometric titrations & precipitation titrations

Blank

background spectrum, used to remove the absorbance of the solvent, taken of everything except for the analyte (indicator)

What else could have been extracted from the spinach leaf?

basically anything that is visible in organic solvent would have been extracted, though not everything absorbs in UV-vis

Methods to determine whether clay or charcoal is better must

be able to measure the concentration of the dye remaining after removal of adsorption agent

Why is it difficult to use colligative properties to measure the concentration of procion red?

because its melting point >300 c. However you can use acid-base titration to measure the concentration of procion red, because it is a weak base

Intercalation role w/clay

bentonite clay has cationic and anionic layers which gives it a large surface area and allows molecules to slide between the layers to adsorb

Higher Reducing Potential means

better at oxidizing stuff/ it gets reduced is more positive

Other indicators besides BB could work if....

both forms are colored like thymol blue and cresol red

Indicator in equilibrium constant experiment

bromothymol blue

BB-

bromothymol blue in blue solution

HBB

bromothymol blue in yellow solution

research project equation

c = A/ (slope * V)

Steady-State Approximation

can be used when the differential rate law for an intermediate is equal to zero. Means the change of concentration of a species is zero, which happens if the intermediate is consumed as quickly as it is formed

Energy

capacity to do work

most easily reduced (highest E value) goes in

cathode

reduction occurs in the

cathodic half cell

E(cell) > 0

cell can do work

Chemical compound used in spectrophotometry lab

chlorophyll A

Model PAH form

completely flat because of it is comprised completely of conjugated double bonds, however the dye has tetrahedral centers at 3 atoms, S, S, and NH; additionally there can be rotation at and non-conjugated double bond, causing procion red to be a poor substitute to the model PAH

Color observed by the eye

complimentary to the color absorbed

You run a chromatogram of a mixture of two metal ions. The spot for one metal ion (compound X) has an Rf of 0.450; the spot for the other ion (compound Y) has an Rf of 0.800. Which compound is closer to the origin?

compound X

In the equation for Beer's law, A = ebc, what quantity is represented by "c"?

concentration

c in beers law

concentration in M

Salinity

concentration of NaCl ion in solution, determined in ppt or mol/kg sample

Concentration of water

considered to be very high and any change to it is not significant, can be removed from equation for equilibrium constant

-k1[A]=

d[A]/dt d "change" t "time"

k2[B]

d[C]/dt

Differential rate equation

describes the change in concentration of a species (d/dt [A]) equal to the rate constant multiplied by the concentration of the reactant

Which of the following is an example of applied research?

developing a new drug to treat malaria

Indicator used in precipitation titration lab?

dichlorofluroescein, an adsorption indicator (Fajan's method)

k2 >> k1

differential rate law for B = 0 becausse it's consumed as quickly as it forms compare [A] & [C] without B, making it easier

DMG

dimethylglyoxime

Which of the following is used to calculate Rf ?

distance spot travels divided by distance solvent travels

b in beers law

distance traveled by the light, or path length (cm)

What was the blank in equilibrium exp?

distilled water

Electromotive force (emf) or cell potential

driving force for electrons to go from one electrode to the other

Electrolytic Cell

electrochemical cells that go through a non spontaneous reaction (need to apply electric current) and have an Ecell that is negative

Galvanic/Voltaic Cell

electrochemical cells that go through a spontaneous reaction, and have a measure Ecell that is positive

Lewis acid

electron pair acceptor

Lewis base

electron pair donor

Enthalpy

energy density, amount of energy released per mol under constant pressure

E(cell) < 0

energy must be supplied in order for cell to function

S

entropy

K

equilibrium constant, indicates the rate of forward and reverse reaction

temp can be lower than

eutectic temp, under certain conditions

After equivalence point? precipitation titration lab

excess Ag+ forms a positively charged shel around the solid particles in solution, to which indicator adsorbs and makes a color change

-Q

exothermic

Ultimate goal of equilibrium lab?

find the Ka of bromothymol blue

pKa1

first deprotonation in ex: HCO3 + H+ --> H2CO3

Water flow on map?

flows southwest from Guadalupe River because the area to the northeast is salty from less water, and are to southwest is more diluted from more rainwater

collig prop responsible for survival of cold tolerant species is

freezing point depression

Four colligative properties

freezing point depression, boiling point elevation, vapor pressure depression, osmotic pressure

electrons travel

from anode to cathode

Bases change litmus paper

from red to blue (Bases go to blue)

The salinity of a salt water sample is typically reported in units of parts per thousand, ppt, which can be calculated by:

g NaCl/ g sample x 1000

Absorbs red light, it appears

green

Absorbance units

has no units, or AU for absorbance units

Heat absorbed by calorimeter (surroundings)

has to equal the heat released by chemical reaction (system)

Bronsted-Lowry Base

hydrogen acceptor

Which of the following is not a colligative property?

hydrogen bonding

Bronsted-Lowry Acid

hydrogen donor

Indicators

indicate an endpoint by changing from one color to another color at a certain pH

Silver ions react with chloride ions to form

insoluble white precipitate

Electrolytes

ionic compounds, dissociate to its ions in solution, which increases the concentration of particles in solution

Which of the following is NOT a part of the spectrophotometry experiment (8)?

ions of different metals Cuvettes and Spinach leaves ARE

linear flow rate

it describes the velocity of the solvent as it travels through the column

mobile phase

it is a liquid or gas solvent that carries the sample through the separation phase column

retention time

it is the elapsed time between sample injection and detection

eluent

it is the fluid that enters the column

When can steady state be used for A-->B-->C, where rate constant from A-->B is k1, and B--->C is k2

k2>>>>>k1

Larger the rate constant...

larger that rate of the reaction, and faster the reaction

Ligands in chrom. exp?

ligands are exchanged, turning the metal center different colors, each metal were hydrates (had H2O ligands)

Silver is

light sensitive, silver cations are reduced to silver metal, solutions with fine grey power should not be used

salt bridge

links 2 cells to prevent a build-up of excess charge

Liquid vs. Solid Entropy

liquid has more entropy, when a compound freezes into a solid it decreased in entropy, heat is released into surroundings

Bromothymol blue yellow at?; blue at?

low pH high pH

Higher electronic transition

lower wavelength, absorbs blue

slope of the standard curve

m= Eb m= slope Eb= molar absorptivity * distance travelled

Which of the following is an example of basic research?

mapping the biosynthetic pathway of vitamin B12

supercooled solutions are

metastable

Which of the following is not applicable to paper chromatography?

moblie phase

e in beers law

molar absorptivity in Lmolcm

As a solution is frozen...

more and more pure liquid is frozen, thereby increasing concentration of the solute in solution, the freezing point of a solution if further depressed until all the solvent is frozen

Precipitation Titrations lab samples

one from march (wet month) and april (dry month) taken from San Antonio Bay

Assumption made in equilibrium experiment?

only one reaction involved, the acid-base reaction between HBB and BB-

Absorbs blue light, it appears

orange

Greatest buffering power exists when

pH = pKa

pH equation

pH= -log[H3O+]

Henderson Hasselbalch equation

pH= pKa + log ([base]/[acid])

Henderson-Hasselbach Equation

pH= pKa + log (base/acid)

pka equation

pKa= -log(Ka)

The typical salinity of sea water is 35:

parts per thousand grams of sea water

Which of the following best explains why you should use pencil to write on your chromatography paper:

pen ink can dissolve in the chromatography solvent while pencil will not

Indicator used for NaOH standardization?

phenolphthalein

colligative property

physical property of solutions that depends on the number of dissolved solute particles in solution, but not the identity of the solute

Isosbestic Point

point where the three spectra (yellow green and blue) intersect- 500nm. When a chemical reaction involves a pair of substances with this point, the absorbance at this wavelength remains constant, regardless of the extent of the reaction or position of chemical equilibrium, existence proves that we can make the assumption of one reaction

PAH

polycyclic aromatic hydrocarbons

Cathode is

positive where reduction takes place

salinity is reported in

ppt

equivalence point is defined as being the point at which

precipitate no longer forms

Standard deviation

precision (deviation from average) usually has to do with assumptions that affect every measurement the same way

Calorimeter assembled by

putting two styrofoam cups together and weighed, then an exact mass (50 mL) of cold water was added, another 50 ml of hot water was boiled, and added to cold, and the change in temp and final mass of cup with water was recorded

ΔS(surr)=

q/T(surr)

q=mc∆T

q= heat flow c= specific heat m= mass ∆T= change in temp.

∆H=

qp/n

-Qsystem=

qwater+qcalorimeter

k

rate constant

R

rate of a reaction

What causes the dark color that forms when solutions of silver nitrate are exposed to light?

reduced silver metal

Fajan's method

relies on the use of an adsorption indicator, dichlorofluorescein- a weak organic acid

Ecell

represents the difference in electrical potential of each of the half cells

pKa2

second deprotonation in ex: CO3 2- + H+ --> HCO3-

Buffer in experiment was

sodium carboante, diprotic

1st Law of Thermodynamics

states that the total energy of the universe is constant or energy cannot be created or destroyed, merely converted to another form

Which of the following is NOT used in the spectrophotometry experiment?

sulfuric acid

Eutectic Temperature

temperature at which the solvent is still a liquid

eluate

the fluid that exits the column

In this experiment (14) we use the spectrophotometer to measure

the ratio of the concentration of the anionic and protonated forms of bromothymol blue, [BB-]/[HBB]

stationary phase

the separation medium that is bounded to the surface of the particles packed in a column

no matter where the slow step is (k1 or k2), C cannot be formed faster than

the slowest rate

eutectic temp

the temperature at which the solution becomes saturated the lowest temp at which the solvent is still a liquid

The brilliant colors associated with transition metal ions or compounds are usually the result of:

the transition of an electron from a lower energy d-orbital to higher energy d-orbital

The highest concentrations of ground level ozone usually occurs in big cities in the afternoon because:

there are more cars on the roads in these cities which increases the level of incompletely combusted hydrocarbon fuels and the high temperature in the afternoon accelerates the formation of ozone

One calorie is equal to 4.184 J. How many significant figures does this number have?

this number is exact

Argentometric Titrations

titrations using silver nitrate

why spot multiple times?

to facilitate visualization by having a higher compound concentration

Which of the following is not used to describe the concentration of a solute in solution.

transmittance

Spectrum in equilibrium exp?

two lamb maxes, one for yellow at about 400 nm and one for blue at about 600 nm, lambda max for blue is chosen because the lambda for yellow still shows some absorbance for the blue solution, and absorbance=0 is desired to quantify concentration

Which of the following is not an objective of the spectrophotometry experiment?

use of acidic and basic solutions

A voltaic cell

uses a spontaneous redox reaction to transfer chemical energy into electrical energy

Why do we measure absorbance at the wavelength where the chlorophyll has the maximum absorbance (i.e. λmax) in this experiment?

using λmax decreases the error of the measurement because the instrument can detect the difference better between a blank and a sample with the chlorophyll-a present

absorbs yellow light, it appears

violet

endpoint

when the indicator changes color

y=1776x (sample equation)

y=absorption 1776= e*b x= concentration aka M

Arrhenius acid

yields H+

Arrhenius base

yields OH-

Add titrant in smaller amounts when

you see pH increasing faster

Reduction potential for SHE is set at

zero

ΔS(univ)=

ΔS(sys) + ΔS(surr)

2nd law of thermodynamics

ΔS(sys) + ΔS(surr) > 0

Equation for freezing point depression and molality

∆Tf= Kfm