Chem 1212L quizzes

Calculate the initial concentrations of Fe3+ ions when these solutions are mixed: 6.00 mL of 0.00180 M KSCN,5.00 mL 0.240 M Fe(NO3)3and 14.00 mL of 0.050 M HNO3.

.0480 M (5.00 mL) x (0.240 M Fe(NO3)3) x (1 mol Fe{3+} / 1 mol Fe(NO3)3) / (6.00 mL + 5.00 mL + 14.00 mL) = 0.0480 M Fe{3+}

If in part one, 4.436 g of NaOH was weighed out. To the correct number of significant figures, how many moles of NaOH is this? (Units not required.)

.1109

Question 1010 / 10 points Transmittance is defined as the fraction of the original light that passes through the sample. T=P/Po where Po is the original and P is after passing though the cell. You will measure T on the instruments. A=log10(Po/P)= -log T or 2.00-log(%T) or abs. If %T = 46 % what is A?

.34

How many grams of magnesium metal should be used in trial 1?

.6g

How many grams of magnesium metal should be used in trial 2?

.8g

If the pressure of gas inside the eudiometer is 735.4 mm Hg after a reaction of magnesium metal with excess hydrochloric acid and the vapor pressure of water inside the tube is 23.4 mm Hg, to four significant figures, what is the pressure of hydrogen gas inside the tube in atm.

.9368 (turn into atm and subtract .9676- .0308)

How many cuvets do you need? (absorption vs concentration)

1

Which of the following can change the rate of a chemical reaction? 1. temperature2. reactant concentration3. catalyst

1,2,3

What is the pKa of acetic acid? Look in your textbook.

4.75

What is the wavelenght range of the visible spectrum in nanometers. (Refer to your lecture textbook for help)

400 to 700

If b= (1.000x10^0) , c= (3.10x10^-3) , A= (1.5600x10^-1) what is the molar absorbtivity 'a'?

5.03x10^1

Identify the type(s) of notebooks that are acceptable laboratory notebooks

bounded notebook

What must you bring with you to lab class next week and every week thereafter?

bounded notebook, pen for recording data

How will the heat of formation for MgO be found ?

by using hess's law

The slope is calculated from the graphs as:

change in molarity over change in time

True or False: I will also measure an unknown and I will plot that on my curve as well.

false

True or False: In using the spectrophotometer, I pour the liquid directly into the instrument.

false

What is the derived relationship between molar mass and delta T?

((Kf)(mass of solute)(i))/((kg solvent)(MW))

What are the units of Kf?

degree C/m

What density will we be using for the HCl ?

1.01 g/mL

In part #2, Trial #1 - How many grams of magnesium oxide should be used?

1.5g

If Absorbance is dimensionless, b is in cm, and c is in molarity what is the unit for 'a' the molar absorbtivity (Beers Law)?

1/(Mxcm)

Given a measured circumference of 35.6 cm, what is the diameter ?(Do not need units / Watch your Sig. Figs / The #s change each time)

11.3 (d=c/pi)

Given 1.00 M NaOH, what is the pH?

14

(Part one Heat of Solution)If 4.436 g of NaOH was added to 150.0 mL of waterand we assume the density of water to be 1.000 g/mLthen what is the total mass? (Watch your Sig. Figs and units are not required)

154.4

A student prepared this solution by mixing the following solutions: 4.00 mL of 0.00250 M Fe(NO3)3 3.00 mL of 0.00250 M KSCN 3.00 mL of 0.050 M HNO3From a plot of absorbance versus concentration of [Fe(SCN)]2+, the equilibrium concentration of [Fe(SCN)]2+ was determined to be 2.8 x 10-4 M. Calculate the initial concentration of Fe3+ before the system is allowed to proceed to equilibrium.

1x10^-3

How many different data sets will you collect ?

2 For the pure solvent. 2 For the solvent with known impurity. 2 For the solvent with "unknown" impurity.

In part #2, Trial #2 - How many grams of magnesium oxide should be used?

2.0g

Given 1.00 M acetic acid, what is the pH?

2.38

How many milliliters of hydrochloric acid solution should be placed in the eudiomenters?

20 mL +/- 10%

For the rate expression in the previous question, what is the overall order of the reaction?

3

What should be the numerical value for the slope of the line that you will produce in the graphing exercise on pg. 1. (to 3 sig. figs).

3.14

For the following reaction, A + B + C -> D + E, the rate expression is first order with respect to reactant A, zero order with respect to reactant B and second order with respect to reactant C. What is the numerical value of the rate constant, k, if the rate = 2.24e-4 mole/lit-min when the [A] = 0.0050M, [B] = 0.250M, and [C] = 0.0112M?

3.6e2

The heat capacity of the solutions that in this experiment can be approximated to what value ?

4.06 J/ g C

When 50.0 mL of 1.00 M HCl is added to 40.0 mL of NaOH and a temperature rise of 11.4 C is observed, what is the heat produced in kJ. (Information about density and specific heat is in the manual and in earlier questions in this quiz.)

4.21 kj

Calculate the initial concentrations of SCN- ions when these solutions are mixed: 6.00 mL of 0.00180 M KSCN, 5.00 mL 0.240 M Fe(NO3)3 and 14.00 mL of 0.050 M HNO3.

4.32x10-4

If you assume this reaction is driven to completion because of the large excess of one ion, what is the concentration of [Fe(SCN)]2+ that would be formed from 6.00 mL of 0.00180 M KSCN 5.00 mL 0.240 M Fe(NO3)3 and 14.00 mL of 0.050 M HNO3.

4.32x10-4. Start with the first solution: since there is complete dissociation, there will be 0.00180M SCN- ions (and 0.00180M K+ ions). So now you are just diluting it because you aren't adding any more ions: C1*V1 = C2*V2 C1 = initial concentration = 0.00180M V1 = 6mL = 0.006L C2 = unknown V2 = 6mL + 5mL + 14mL = 0.025L Solve for C2: C2 = C1*V1/V2 = (0.00180)*(0.006)/(0.025) = 4.32*10^-4 M

Lets say that the heat produced when 4.436 g of NaOH was added to a water solution was 6.123 kJ. To the correct number of significant figures, what is the calculated heat of solution in kJ/mole? (Units not required.)

55.21 (deltaH=q/n)

Given a measured diameter of 18.0 cm what is the circumference? (Do not need units / Watch your Sig. Figs / The numbers change each quiz)

56.5

Given that the temperature change observed is 11.5 Cwhen 4.436 g of NaOH are added to 150.0 mL of water.What is the heat energy in kJ that is produced. (The specific heat of the solution is 4.06 J/ g C.) (Units not required.)

7.21 (q=mcdeltaT)

A student prepared this solution by mixing the following solutions: 4.00 mL of 0.00250 M Fe(NO3)33.00 mL of 0.00250 M KSCN3.00 mL of 0.050 M HNO3From a plot of absorbance versus concentration of [Fe(SCN)]2+, the equilibrium concentration of [Fe(SCN)]2+ was determined to be 2.8 x 10-4 M. Calculate the initial concentration of SCN- before the system proceeds to equilibrium.

7.50x10^-4

A student prepared this solution by mixing the following solutions: 4.00 mL of 0.00250 M Fe(NO3)33.00 mL of 0.00250 M KSCN3.00 mL of 0.050 M HNO3From a plot of absorbance versus concentration of [Fe(SCN)]2+, the equilibrium concentration of [Fe(SCN)]2+ was determined to be 2.8 x 10-4 M. Calculate the equilibrium constant.

827

When 50.0 mL of 1.00 M HCl is added to 40.0 mL of 1.00 M NaOH what is the total mass of the solution assuming that the density of both dilute aqueous solutions is 1.01 g/mL? (Correct significant figures, no units required.)

90.9g

In the first graph of Temp(T) versus time, once the response levels out, what is observed?

A constant decrease in temperature until the entire system reaches room temperature.

Which of the following is/are valid heat of formation equations?

C graphite (s) + O2 (g) ---> CO2 (g)

Which of the following is acceptable?

discussing lab results w partner, writing lab report in own words

Which of the following is NOT a valid heat of formation reaction. (standard enthalpy of formation)

CH4 (g) + 2 O2 (g) ----> 2 H2O (g) + CO2 (g)

When performing the graphing exercise the five data points should . . .

Have one best fit straight line averaging the points

The purpose of this experiment is to (ideal gas law)

Experimentally determine the ideal gas constant R.

Which of the following statements is true?

It is my responsibility to keep up with the laboratory schedule given on the web based platform (D2L) so that I will be prepared for the correct lab experiment each week.

All the information should be written in your lab notebook and not on the sheets provided. What will you be determining and writing in your lab book?

I will be reporting the transmission values in my notebook and then convert them afterwards to absorbance using the formula A=2-log(%T).

All the information should be written in your lab notebook and not on the sheets provided. What will you be doing for the calculations ?

I will graph using Excel the absorbance versus the concentrations given and using the slope to back calculate the concentration from the observed absorbance.

Why must the mass of magnesium metal used in the eudiometer tube be limited?

If you use too much mass of magnesium, the hydrogen gas produced will fill the eudiometer tube beyond the volume markings and its volume will not be able to be determined.

What are the units of the rate constant, k, in question 3?

L^2/min-mol^2

When 50.0 mL of 1.00 M HCl are added to 40.0 mL of 1.00 M NaOH and allowed to react, what is the limiting reagent?

NaOH

For the experiment today, which concentrations of S2O82- and I- are used to solve for x, y, and k in the rate expression, rate = [S2O82-]x[I-]y?

The initial concentrations of the reactants, S2O82- and I-.

1g

The mass of the non-volatile, non-electrolyte solute will be:

There is a prelab quiz associated with each laboratory experiment. Identify every statement that is true about the prelab quizzes.

The prelab quizzes should help me understand the procedures and calculations for the lab experiments. The quizzes must be completed by 11:55PM the night before my scheduled lab time. I get three chances to take each quiz and the highest quiz grade is saved. I get to drop the two lowest quiz grades at the end of the semester.

Why is it advantageous to use solvents which have large Kf constants when performing a freezing point depression experiment?

To produce a large recordable temperature change for a small amount of solute.

Your lab notebook must have a Table of Contents and numbered pages.

True

The heat capacity of a solid is different than the heat capactiy of a liquid. Therefore when "cooling" the liquid will cool at a different rate than the solid. When you graph your data the slope of each of these cooling curves will intersect. That intersection is typically the Freezing point.

You will need to produce a graph like this one for your report.

What is the 'known' acids and bases used in this experiment?

acetic acid and sodium hydroxide

When measuring items in the lab (Pg. 1) you are to measure . . .

any round item

{select the best answer} The mass of magnesium metal used when doing this expriment should be . . .

between .035-.045g

When calculating the ideal gas constant R, what are some common mistakes that are made ? [select all that are correct]

forgetting to convert the T to K, forgetting to convert to the V to L, forgeting to convert P from torr to atm, forgetting to subtract vapor pressure of water.

What is the name of the accepted standard state for carbon?

graphite

Some of the goals of the experiment include

ice table, quadratic, calibrate spectrophotometer, convert from transmittance to absorption

What should be done with the left over reservoir after the experiment is over?

in the waste container labeled PV=nRT

your lab instructor is

is very willing to answer your questions. Come by during office hours, email at any time, or set up an alternative time to meet with your instructor if the office hours do not meet your needs.

What is the name of the solvent you will be using ?

lauric acid

The pressure INSIDE the eudiometer when column of liquid inside the tube is higher than the reservoir is . . .

less than atmospheric pressure

Will the freezing temperature after the solute is added be higher, lower or the same?

lower

The effect of a catalyst is to

lower the activation energy of a reaction.

The beaker of water into which you invert the eudiometer tube should . . .

need only cover the open end of the eudiometer.

The calorimeters that are used have a large top cup with a hole for the thermometer and a small bottom cup for the reaction to take place. Which portion of the apparatus may be thrown away?

neither part may be thrown away. They are reused

NaOH will QUICKLY digest the mucous membrane of your eye. Be sure to wear your safety glasses and remember "it may not be YOU that has the accident but it could be YOU that gets hurt."

ok

Sodium Hydroxide (NaOH) is very dangerous. Please observe all safety precautions and notify the TA of any spill, solid or liquid. He or she will gladly clean it up for you but you have to notify them of the spill. Thanks.

ok

10% is deducted from late lab reports daily up until ________, when the grade of zero will be assigned.

one day after the due date

A good notebook has the following characteristics.

organized, table of contents, shows evidence of being used w original date, new lab writeups are started on a new sheet, procedure on right hand pages and left for work and notes

All of the following would be expected to affect the INITIAL rate of a chemical reaction EXCEPT

removing some products

What temperature should be used in the calculations ? (ideal gas law)

room temperature in K

As from Question 1, 2. The reaction is performed in a glass reaction vessel; HF (g) attacks and reacts with glass.

shift to the left

UO2 (s) + 4HF (g) -> UF4 (g) + 2H2O (g)This system has already reached equilibriumWhat is the affect on the position of equilibrium ifwater vapor is increased and the pressure did not change?

shift to the left

2. UO2 (s) + 4HF (g) -> UF4 (g) + 2H2O (g)This system has already reached equilibrium.Predict the affect of the position of equilibriumif water vapor is removed.

shift to the right

UO2 (s) + 4HF (g) -> UF4 (g) + 2H2O (g)That this system has already reached equilibrium.Predict the affect on the position of equilibrium ifHF is added to the system.

shift to the right

UO2 (s) + 4HF (g) -> UF4 (g) + 2H2O (g)This system has already reached equilibrium. Predict the affect of on the position of equilibrium ifboth equal moles UF4 and H2O are removed.

shift to the right

UO2 (s) + 4HF (g) -> UF4 (g) + 2H2O (g)This system has already reached equilibrium. What is the effect of each on the position of equilibrium if the volume is decreased.

shift to the right

When are laboratory reports due?

the following lab meeting at the beginning of the scheduled lab time

What will be in your laboratory notebook when you arrive for lab class next week and every week thereafter?

title,purpose,listofchemicals and equpment,outline of procedure,place to record data

The reading from the spectrometer should be made in transmittance and converted to absorbance because?

transmittance is linear

True or False : I will find the equation of the line by linear regression on the computer graphing program and use it to find the concentration of my unknown.

true

True or False: I will graph a calibration curve of absorbance as a function of concentration with 6 data points (including zero) using a computer graphing program. I need to calculate the concentration and the absorbance first before plotting.

true

True or False: When testing samples in the same cuvet, one should always test in the order from the most dilute to the most concentrated.

true

1. For the following 10 questions use the following reaction system.UO2 (s) + 4HF (g) -> UF4 (g) + 2H2O (g)Suppose that this system has already reached equilibrium. Predict the affect of each (1-10) of the following changes on the position of equilibrium. Additional of UO2 is added to the system.

will not change or be affected

UO2 (s) + 4HF (g) -> UF4 (g) + 2H2O (g) This system has already reached equilibrium.What is the affect of on the position of equilibriumif the lights in the room are turned off.

will not change or be affected

UO2 (s) + 4HF (g) -> UF4 (g) + 2H2O (g)This system has already reached equilibrium.Predict the affect on the changes on the position of equilibriumif A catalyst is added.

will not change or be affected

UO2 (s) + 4HF (g) -> UF4 (g) + 2H2O (g)This system has already reached equilibrium. Predict the affect on the position of equilibrium if Helium gas is added.

will not change or be effected

Identify everything that is OK to do in your laboratory notebook.

write in pen, enter data. draw line through mistakes

Using the following information, what are the values of the exponents in the rate expression, rate = k[A]x[B]y initial concentration of A, initial concentration of B, rate Experiment 1: 0.050M, 0.050M, 0.062M/sec Experiment 2: 0.050M, 0.100M, 0.123M/sec Experiment 3: 0.100M, 0.100M, 0.491M/sec

x=2 y-1

Should you overlay the graph of the solvent with impurity over the graph of the pure solvent?

yes