lab final
washed with soap and water
) If either stearic acid or lauric acid is spilled on the skin, it should be
> 10−7 M
Acidic solutions have a hydronium concentration, [H3O+ ] that is which of the following?
darker red
Add 0.05 M NaSCN
darker red
Add 0.10 M Fe(NO3)3
All wastes should be put into the large waste container designated by your instructor.
At the end of the Equilibrium and Le Châtelier's Principle experiment, wastes should be disposed of in the following way.
solutions with concentrations greater than 0.1 M
Because acid-base reactions are highly exothermic, which of the following should you NOT mix together?
blue to pink
CoCl42−(aq) + 6 H2O(l) equilibrium reaction arrow Co(H2O)62+(aq) + 4 Cl −(aq) goes from
a proton
Conjugate acid-base pairs differ by which one of the following
deep red
Control for Comparison
Fe, right, SCN -
Fe3+ + SCN − equilibrium reaction arrow FeSCN2+ When Fe(NO3)3 was added to the system: (a) Which ion in the equilibrium system caused the '"stress"? Which way did the equilibrium shift?When NaSCN was added to the system: (a) Which ion in the equilibrium system caused the '"stress"?
colorless to red
Fe3+(aq) + SCN −(aq) equilibrium reaction arrow FeSCN2+(aq) goes from
flush with water, Have your lab partner notify the instructor about the spill while you continue rinsing with water.
If 12 M HCl is splashed onto the eyes or skin, what is the proper response?
entropy
If a process is spontaneous and endothermic, the change in ---------- must be positive
higher
If process is endothermic, process will be spontaneous when Trxn is ------------ than the temperature required for ΔH = TΔS
an increase in the volume of the titrant required to reach the end point and an overestimation of the number of moles of analyte present
If you condition the receiver Erlenmeyer flask with the analyte solution prior to adding the measured volume of analyte to be titrated, what is the effect?
4.5
Kf of stearic acid is
C2H3O2- + H2O → HC2H3O2 + OH-
Once the ionic solid has dissolved, the anion that is formed is able to react as a base, with water as the acid. Write the net acid-base reaction that occurs when dissolved NaC2H3O2 reacts with water.
d
Once the reading on the analytical balance stops fluctuating, which of the following are true? (Select all that apply.) You should memorize it so you can write it in your lab notebook later. You should record the mass on a piece of scrap paper to be transferred into your lab notebook later. You should ask your lab partner to record it in their lab notebook. You should record the mass in your lab notebook with a pen.
HCl, KMnO4
Select the chemicals in this experiment that are listed as acidic or corrosive 13
Diluting a strong acid results in a lower concentration of hydronium, which increases the pH. Diluting a strong base results in a lower concentration of hydroxide, which decreases the pH.
State a general rule about what happens to the pH of acidic or basic solutions when they are diluted with pure water.
nonhazardous, irritation
Stearic and lauric acids are ------ but prolonged contact with skin may cause ----
deionized water, phenyltaline, vinegar
The Erlenmeyer flask should contain which of the following at the beginning of the experiment?
enthalpy
The amount of heat energy given off or absorbed by a process at constant pressure is the change in
soluble
The lower the charges on the ions in an ionic solid, the more ------ the solid is
placed into the container for used metals.
The metals from Part A2 of the experiment should be removed from the reactions with forceps, rinsed with water if they have been exposed to acid, blotted with a paper towel to remove excess water, then placed into the container for used metals.
oxidizing agents
The solutions from Part A1 of the experiment should be rinsed into the waste container for
none listed
Vinegar and phenyl thaline is listed as which of the following? corrosive irritating vapors toxic if ingested causes staining on skin flammable none listed
freezing point depression
What common colligative property will you be exploring in 8
all the reducing agents
What produces hydrogen gas in this experiment 13?
View the etched line on the volumetric flask at eye-level. not above or below
When reading the meniscus of a volumetric flask, which of the following are acceptable?
Rinse with vinegar solution several times.
When the procedure says "condition the graduated cylinder with vinegar before using it", what does that mean?
hydronium ions water molecules conjugate base ions
Which are the only species present when a strong acid reacts with water?
it causes dark spots
Why should silver nitrate be handled carefully?
A-D, A-C
acetic acid (HC2H3O2) ammonia (NH3) hydrochloric acid (HCl) sodium hydroxide (NaOH) water (H2O) which are corrosive and which have harmful vapors
1:1
c) What is the stoichiometry of NaOH to vinegar in the neutralization reaction?
placed in the labeled container
his exercise deals with waste disposal in the Freezing Point Depression experiment. Choose the answer that best completes the following statement. All wastes should be
entropy
is related to the number of ways the energy of the system can be distributed.
reducing agents
produce hydrogen gas when exposed to water and/or acid. Keep the reactions away from ignition sources, and rinse acid off metal before discarding it. Do not tightly cap thewaste container.
it increases
what happens to Kw if tempreture increases
lauric acid, 200.32
what solute is used for experiment 8 and what's its mass
tongs, spatula, graduated cylinder, beaker, digital thermometer, hot plate, no crystallization dish
According to the directions for this experiment, which pieces of equipment will you use for this experiment? (Select all that apply.) tongs test tube ruler spatula graduated cylinder spectrometer crystallization dish thermistor beaker digital thermometer Erlenmeyer flask hot plate
decolorizes and precipitate forms
Add 1.0 M AgNO3
no significant chnage
Add 1.0 M NaNO3
a and b
After transferring all of the solid from a weighing beaker into a volumetric flask, which of the following describes the step or steps to finish making the solution? Fill the volumetric flask with a significant volume anywhere from about from half-way to where the neck narrows. Stopper the flask and invert a few times to ensure complete mixing and that the solid is completely dissolved. Once the solid is dissolved, fill the volumetric flask almost to the etched line and finish adding solvent dropwise until the bottom of the meniscus is touching the etched line. Fill the volumetric flask all the way to the etched line, stopper it and invert a few times to ensure complete mixing and that the solid is completely dissolved. Once the solid is dissolved, fill the volumetric flask almost to the etched line and finish adding solvent dropwise until the top of the meniscus is touching the etched line.
Na+ and NO3− are not present in the equilibrium equation, and do not affect the concentration of FeSCN2+ which is responsible for the coloration.
Choose the best explanation for the result you observed when NaNO3 was added.
HCl
Choose the chemical in this experiment that has irritating vapors in 13.
.01 ml
How accurate are the volumes measured with a serological pipet?
Keep reactions away from ignition sources, and rinse metal before discarding it.
How should accidents be prevented when working with the reactions that produce hydrogen gas, which is flammable?
less
If process is exothermic, process will be spontaneous when Trxn is -------------- than the temperature required for ΔH = TΔS
an increase in the volume of the titrant required to reach the end point and an overestimation of the number of moles of analyte present
If you rinse your buret with deionized water, but do not condition with the titrant solution, what is the effect?
he excess material should be considered waste and disposed of properly.You should use the spatula provided to remove excess material.
If you significantly overshoot your target weight on an analytical balance, which of the following actions are correct?
nonspontaneous
If ΔH is greater than zero, and ΔS is less than zero, the process is always
% difference = ((theoretical value − actual value) × 100%) / theoretical value
In Part B, for the first solution made by adding lauric acid, calculate the % difference. The equation for percent difference is:
lower
In Part B, for the first solution made by adding lauric acid, did you expect the freezing point to be at a higher or lower temperature than that of the pure solvent stearic acid?
free energy
In a nonspontaneous process,------is the amount of energy that must be supplied to cause the process to occur.
6.25e3, .638 m, 3.6C, 74.2 C
In an experiment, you use 9.800 g of solvent (FP = 77.8°C; Kf = 5.7°C/m) and 0.810 g of solute (molecular mass = 129.55 g/mol).How many moles of solute have you used? What is the colligative molality of the solution formed? What is the predicted freezing point depression ΔTf?What is the predicted freezing point of the solution formed?
CoCl42−(aq) + 6 H2O(l) equilibrium reaction arrow Co(H2O)62+(aq) + 4 Cl −(aq)
Only one of the reactions is heated as part of the le CHaltier experiment. Which is it?
The usual rules about appropriate clothing and safety glasses must be observed.Food and beverages are never permitted in labs.
Select all responses which correctly address safety issues in the Equilibrium and Le Châtelier's Principle lab.
CoCl42−(aq) + 6 H2O(l) equilibrium reaction arrow Co(H2O)62+(aq) + 4 Cl −(aq) Fe3+(aq) + SCN −(aq) equilibrium reaction arrow FeSCN2+(aq)
Several reactions will be studied in the Equilibrium and Le Châtelier's Principle experiment. Select the correct ones from the list below.
CO2 + H2O → H2CO3
Show the reaction of CO2 with water to produce carbonic acid (H2CO3)
NaOH solution
The buret in this titration experiment should contain which of the following?
it shifts the equilibrium toward the higher energy side of the equilibrium.
What is the effect of raising the temperature of a system at equilibrium?
Work with it under a hood and avoid inhaling the vapors.
What should be done to avoid exposure to the vapors?
A,B, D, E
What should you do when filling a buret? (Select all that apply.) Make sure the stopcock is closed. Fill the buret below the zero mark. Make sure the stopcock is open. Condition the buret first. Make sure there are no air bubbles left in the buret tip. Fill the buret exactly to the zero mark.
The brush that is provided.
What should you use to clean the weighing pan before and after use?
stearic acid
What solvent is used for this experimentn8
.500g
When a student was weighing out a sample, the balance display read "0.500 g." Which of the following is the correct way to record this value into a lab notebook?
HSO4−
Which of the acids below will have the lowest pH in a 0.000010 M solution of the acid? HClO HCO3− HNO2 HSO4−
freezing point depression vapor pressure lowering boiling point elevation osmotic pressure
Which of the following is a colligative property
They have a small Ka and dissociate to only a small degree
Which of the following is true about weak acids?
Molality includes the moles of solute and the volume of solvent.
Which of the following statements is NOT true he van 't Hoff factor for K3PO4 is 4. Pure water boils at 100°C; sea water boils at a higher temperature. The kf and kb for the same solvent are generally different. The van 't Hoff factor for lauric acid is 1. Molality includes the moles of solute and the volume of solvent.
They should be kept in a labeled beaker at the bench.
While working on the Equilibrium and Le Châtelier's Principle experiment, wastes should be kept in the following way.
highly corrosive so it can injure skin or eyes, vapor is irritant so it should be done under a hood
why must one be very careful when handling concentrated hydrochloric acid (12 M HCl)? (Select all that apply.)
