Chem Lab 8-12

If you significantly overshoot your target weight on an analytical balance, which of the following actions are correct?

- You should use the spatula provided to remove excess material 2- The excess material should be considered waste and disposed of properly.

Highly Irritating Vapors:

- acetic acid (HC2H3O2) - ammonia (NH3) - hydrochloric acid (HCl)

Corrosive

- acetic acid (HC2H3O2) - ammonia (NH3) - hydrochloric acid (HCl) - sodium hydroxide (NaOH)

18. Because acid-base reactions are highly exothermic, which of the following should you NOT mix together?

- solutions with concentrations greater than .1 M

20. How accurate are the volumes measured with serological pipet?

.01 mL

A buret should be read to which nearest mL?

.01 mL

15. When a student was weight out a sample, the balance display read 0.500g which of the follwiing is the correct way to record this into a lab notebook?

0.500g

Van'tHoff for Lauric

1

After transferring all of the solid from a weighing beaker into a volumetric flaks, which of the following describes the step or steps to finish making the solution?

1- Fill the volumetric flask with a significant volume anywhere from about 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. 2- Once the solid is dissolved, fill the volumetric flask almost to the etched line and finish adding solvent drop wise until the bottom of the meniscus is touching the etched line.

Why do you need to be careful while handling 12 M Hydrochloric Acid (HCl)

1- Its vapor is a respiratory irritant, so it should be used in a fume hood 2. It is highly corrosive, and can injure the eyes and skin.

16. In the video called pipetting techinques Lindsey demonstrates the proper use of which of the following?

1- Volumetric pipets 2- serological pipets

17. Befre using a pipet, it should be conditioned. Select the step or steps involved in properly conditioning a pipet.

1- dispose of the reagent into a waste beaker since it is now contaminated with whatevveer may have been on the pipet 2- draw a small volume of reagent into the pipet, turn it sideways and rotate so all the walls are coated with reagent 3. Pour some reagent into a beaker for use with the pipet.

18. When using a bulb with a piept, which of the following are true?

1. The bulb should be held just firmly enough to the end of the pipet to make a seal 2. Once there is solution in the pipet, the bulb should be replaced with a thumb or index finger so liquid can be slowly released to the desired level. 3. Solution should be drawn up only slightly above the calibration mark.

19. Regarding the solution that remains in a pipet after gravity has drained it, which of the following are true

1. The remaining solution in a volumetric pipet should NOT be gently expelled with a pipet bulb to complete the transfer. 2. The remaining solution in a serological pipet should be gently expelled with a pipet bulb to complete the transfer.

Pure water boils @ ___. Sea water boils at a _____ temperature

100, higher

11. What is the stoichiometry of NaOH to vinegar in the neutralization reaction?

1:1

The Van't hoff Factor for K3PO4

4 because K3PO4 -> 3K+ +PO4 ^3- 3+1 = 4

6. In Part D of enthalpy, wat is the most appropriate setting for the stirrer

6

21. Acidic solutions have a hydronium concentration, that is which of the following

>10^-7M

What should you do when filling a buret?

?

What are the colligative properties? What is not

ARE: boiling point, vapor pressure, freezing point, and osmotic pressure NOT: Density Enhancment

What is a suitable container for weighing a solid on an analytical balance

An empty, clean and dry beaker

Only one of the reactions is heated as part of the experiment. Which is it?

CoCl42-(aq) + 6 H2O(l) Co(H2O)62+(aq) + 4 Cl -(aq)

Several reactions will be studied in the Equilibrium and Le Châtelier's Principle experiment. Select the correct ones from the list below.

CoCl42-(aq) + 6 H2O(l) Co(H2O)62+(aq) + 4 Cl -(aq) Fe3+(aq) + SCN -(aq) FeSCN2+(aq)

Equiptment in Freezing Point Lab

Crystallization dish Graduated Cylinder Digital Thermometer Beaker Spatula Tongs Hot Plate

3. Temperatures will be measured with a

DIGITAL THERMOMETER

in enthalpy The chemical solutions are

DILUTE BUT CORROSIVE

14. If ΔH is positive, the reaction is

ENDOTHERMIC

8. The amount of heat energy given off or absorbed by a process at constant pressure is the change in

ENTHALPY

16. If a process is spontaneous and endothermic, the change in ____must be positive.

ENTROPY

____is related to the number of ways the energy of the system can be distributed.

ENTROPY

12. A reaction that gives off eat energy is

EXOTHERMIC

17. In a spontaneous process,____ is the amount of energy that must be supplied to cause to process to occur.

FREE ENERGY

7. ΔG is the symbol for

FREE ENERGY

We'll be exploring

FREEZING POINT DEPRESSION

If 12 M HCl is splashed onto the eyes or skin, what is the proper response?

Flush the affected area with a lot of water. Next: Have your lab partner notify the instructor about the spill while you continue rinsing with water.

1. State a general rule concerning a system at equilibrium when more of one of the components is added.

If a component of the equilibrium reaction is added, the equilibrium will shift toward the opposite side of the reaction to consume the added material.

State a general rule concerning a system at equilibrium when one of the components is removed.

If a component of the equilibrium reaction is removed, the equilibrium will shift toward the same side of the reaction to replace the removed material.

4. Which of these compounds are used in Part B of enthalpy of the experiment

Iron(III) Chloride and Sodium Hydroxide

What is the effect of raising the temperature of a system at equilibrium?

It shifts the equilibrium toward the higher energy side of the equilibrium.

Molality

Moles Solute/Kg Solvent

15. If ΔH is greater than zero, and ΔS is less than zero, the process is always

NONSPONTANEOUS

The buret in this titration experiment should contain which of the following?

NaOH

Vinegar / Phenlphthalein

None listed

Stearic and Lauric Acid (safety)

Nonhazardous Skin Causes IRRITATION Gets on skin: wash with soap and water

K<1

Reactants

condition the graduated cylinder with vinegar before using it means

Rinse with vinegar solution several times

13. A reaction in which ΔG is negative is

SPONTANEOUS

2. In part A of the experiment, a____ is used to dispence _____.

SPOON-TYPE SPATULA , CaCl2 and NH4NO3

11. The part of the universe that interacts with a thermodynamic system is the

SURROUNDINGS

10. In reaction energetics, the ____is the part of the universe being studied

SYSTEM

5. In part C of enthalpy, which compound is put in all the test tubes?

Sodium Hydroxide

What should you use to clean the weighing pan before and after use?

The brush that is provided

23. Which of the following is true about weak acids?

They have a small Ka and dissociate to only a small degree.

When reading the meniscus of a volumetric flask, which of the following are acceptable?

View the etched line on the volumetric flask at eye-level.

19. Conjugate acid-base pairs differ by which of the following?

a 'proton

4. AgCl(s) + 2 NH3(aq) Ag(NH3)2+(aq) + Cl -(aq) K = 3.01 10-3 ΔH > 0 a) which causes more dissolution of the solid? b) which will cause more precipitation of the solid

a) adding NH3, Heating b) adding Cl-, cooling

1. Two gases, A and B, are at equilibrium in a sealed cylinder. Individually, gas A is colorless, while gas B is dark colored. The reaction might be written as A(g)<=>2B(g) a) The cylinder should appear b) When the system is heated, the cylinder's appearance becomes very light colored. Therefore, the reaction must be

a) colorless b) exothermic

14. 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?

an increase in the volume of the titrant required to reach the end point 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?

an increase in the volume of the titrant required to reach the end point an overestimation of the number of moles of analyte present

CoCl42-(aq) + 6 H2O(l) Co(H2O)62+(aq) + 4 Cl -(aq) goes from

blue to pink

What is a reversible reaction?

can proceed in either direction

Why should silver nitrate be handled carefully?

cause dark spots where it contacts the skin.

Fe3+(aq) + SCN -(aq) FeSCN2+(aq) goes from

colorless to red

The Erlenmeyer flask should contain which of the following at the beginning of the experiment?

deionized water phenolphthalein vinegar

The KF and KB for the same solvent are generally ___

different

Solute in Freezing Point lab

lauric acid

K>1

products

A general rule concerning temperature changes to equilibrium systems is that the input of energy (raising the temperature) shifts the equilibrium to the higher energy side of the equilibrium. Based on your observations, which side of the equilibrium is the higher energy side?

reactant

The larger the Ksp value, the more product that is formed at equilibrium. The lower the charges n the ions in an ionice solid, the more

soluble the solid is

Whats the Solvent in the Freezing Point lab

stearic acid

The amount of analyte equals

the amount of titrant added.

safety issues in the Equilibrium and Le Châtelier's Principle lab

usual rules about appropriate clothing and safety glasses must be observed 2- Food and beverages are never permitted in labs.

When is equilibrium established?

when the rates of the forward and reverse reactions are equal