CHM 113: Superquiz

Adipic Acid: % recovery

% recovery = weight of pure/weight of crude x100%

Freezing Point Depression: Kf equation

(delta)T = Kf x m

Conduct. & Grav. Det: Name three requirements for gravimetric analysis to work

-accurate weight -no contamination for other precipitates to form -accurate titration of H2SO4 into Ba(OH)2

Conduct. & Grav. Det: How fast should the drip rate be to obtain accurate readings from the drop counter?

1 drop per 1 second

Density: What is the density of water at usual reference temperature?

1 g/mL

Gas Laws II: conversion for mm to mmHg

1 mmHg = 13.6 mm

Determination of Ka of a Weak Acid: What does the term equivalence point mean?

1/2 of the volume it takes to reach completion of reaction.

Acids and Bases: [H+] equation

10^-pH

Acids and Bases: [OH] equation

10^-pOH

Adipic Acid: What is the worldwide industrial production for adipic acid?

2.2 million metric tons

Density: Density is dependent on temperature. What is the usual reference temperature of water when used to find specific gravity?

4 C

Acids and Bases: What is a base?

A proton acceptor

Acids and Bases: What is an acid?

A proton donor

Gas Laws I: What value will you get from plotting your data that indicated the accuracy of your data? What value indicates that your results for the lab are good data?

A value of at least 0.99 for the r-value indicates accuracy of data.

Determination of Ka of a Weak Acid: If a weak acid is titrated with a strong base such as NaOH will the equivalence point occur below pH 7.0, above pH 7.0 or at pH 7.0?

A weak acid strong base solution is more basic. Equivalence occurs above pH 7.0

Gas Laws I: Lord Kelvin found that there was a specific temperature that was lowest obtainable temperature. What is that temperature value called? What is the temperature value in degree Celsius?

Absolute zero = -273.15 degree Celsius

Gas Laws I: What must you remember to do when adding specified volumes to the tubing?

Add 5 mL to everything

Freezing Point Depression: Where is freezing point seen on the graph of temperature vs. time?

Freezing point is seen on a T v V graph as the flat line where temperature does not change.

Freezing Point Depression: What is the difference between the freezing point and melting point of a substance?

Freezing point is the temperature where a substance changes liquid to a solid. Melting point is the temperature where solid goes to liquid.

Adipic Acid: Molecular formula od adipic acid

H2C6H804

Determination of Ka of a Weak Acid: Acetic Acid is a weak acid. Write the equation shown the reaction of this acid with water. Label phases and conjugates.

HC2H3O2 + H2O ----> H3O+ + C2H3O2- Acid Base CA CB

Gas Laws II: In this experiment, we fill a buret with concentrated acid and then add water. This breaks the rule saying never add acid to water. Why can we safely do this here?

HCl is more dense than H2O so there are two layer and H2O is on the top so when inverted the acid does not mix with the water.

Acids and Bases: Define pH and equation

pH= -log[H+] measure of H+ ions in a solution

Acids and Bases: pOH equation

pOH= -log[OH]

Conduct. & Grav. Det: define qualitative analysis

physical characteristics, compounds or elements present

Adipic Acid: Adipic acid is not soluble in cold water.

False.

Types of reactions: Mg2+ is twice as more conductive as Na+?

False. Mg2+ is polarized and has drag so only slightly more conductive, not twice.

Adipic Acid: Why do we used fluted filter paper?

Fluted paper has folds that have a larger surface area so the solution can filter faster.

Adipic Acid: Given information in the manual, predict the solubility curve vs. temperature for adipic acid in water.

As temperature rises, solubility of adipic acid increases. A directly proportional line.

Gas Laws I: Explain Boyle's Law and what variables must be plotted to provide a linear relationship

At constant temperature, a gas occupies a volume that is inversely proportional to pressure. Must have initial and final pressure and volume. P vs 1/V is directly proportional. P1V1=P2V2

Acids and Bases: When using litmus paper in the presence of a base what color does it turn? In the presence of an acid?

Blue in bases Red in acids

Acids and Bases: Why are we boiling cabbage in todays lab? What happens if you boil it for too long and why?

Boil cabbage to soften so the pH can be tested. Boiling for too long takes away its pigment and denatures it so pH can't be tested.

Types of reactions: What is the conductivity of a solution? How do the size and charge of ions affect the conductivity of a solution?

Conductivity of a solution is the ability to conduct electricity. Higher concentration of ions leads to more conductivity. Given ions of the same charge, smaller ions conduct electricity better. High charged ions conduct better than lower charged ions but higher charged ions are more polarized causing drag.

Adipic Acid: why is thee a difference between these two melting points?

Crude adipic acid is not pure- it is contaminated which results in a different melting point than pure adipic acid.

Density: Why is density an important physical property?

Density can be used to identify an object because it is a unique characteristic of a substance.

Density: Why do some things have high density and others have low density?

Density is dependent on the arrangement of atoms of an object. Loosely arranged atoms lead to lower density while tightly packed atoms lead to higher density.

Density: What is the difference between density and specific gravity?

Density is the ratio of mass to volume (d=m/v). Specific gravity is the ratio of one substance to the density of water.

Types of reactions: Name the reactions we look at in this experiment

Double displacement acid-base redox combustion gas evolution precipitation single displacement

What could Careless Curt have done wrong to make the adipic acid melting point 15 degrees below literature value?

He messed up filtration and ended up with impure crystals.

Types of reactions: What would you expect to happen in an endothermic reaction?

Heat is absorbed resulting in a decrease in temperature.

Adipic Acid: The melting point in Careless Curt's adipic acid was 15 degrees below the literature value. Was the acid pure or impure?

Impure due to contaminations that change the melting point.

Adipic Acid: Why is it not a good idea to pour liquid directly into the center of the filter paper?

It will break the filter paper. Pour down the sides.

Gas Laws II: What would happen if the Mg ribbon were left out and a layer of MgO formed on it and was not rubbed off with the steel wool? What would happen to your results?

Mg would not react with HCl in the way we want it to for the experiment.

Freezing Point Depression: What is molality? What is molarity? Why is molality used when defining the freezing point depression constant?

Molality (m) = moles solute / kg solvent Molarity (M) = moles solute / L solution Use molality because mass does not change with temperature like volume does

Adipic Acid: What greenhouse gas is produced during synthetic process of adipic acid?

N2O which leads to global warming

Density: What are the units of specific gravity?

None. Units cancel out.

Gas Laws II: Pg=Pb-Pwv-Pw stands for?

Pg= dry gas pressure Pb= barometric pressure Pwv= water vapor pressure Pw= water pressure

Gas Laws II: Pw equation? and why do we divide by the denominator?

Pw= (delta)h/13.6 13.6 is conversion factor from mm to mmHg

Acids and Bases: Universal indictor color means

ROYGBIV Acidic (red)------basic(violet)

Adipic Acid: This lab is based on separation of a pure substance from impurities. What property of acidic acid is used in the seperation?

Solubility

Adipic Acid: What property will we use to separate and isolate adipic acid from impurities? Is this an intensive or extensive property?

Solubility which is an intensive property.

Freezing Point Depression: Explain what is meant by supercooling? Where is it on the graph?

Supercooling occurs when the solid is cooled below its freezing point but the energy is used to make the solid so the temperature stays the same. Supercooling can be seen immediately before the freezing point.

Gas Laws II: How would your value for the equivalence weight be affected if some of the H2 gas produced during the reaction of Mg (s) and acid escaped from the gas buret?

The equivalence weight would be higher than what it actually is.

Conduct. & Grav. Det: Suppose the barium sulfate weight in the crucible above was not completely dry. How would this affect the concentration calculated for the barium hydroxide solution?

The mass will be higher than it should be because there is more product. The calculated concentration is different from the actual concentration.

Gas Laws II: Why is it important to calculate the volume of the "dry gas"?

The pressure of the wet gas contains impurities such as water vapor. The volume of dry gas will be used to calculate the amount of H2.

Freezing Point Depression: Why does the introduction of a solute into a solution change the freezing point? how does the freezing point change?

The solute disturbs normal molecular interactions and causes lower freezing point because more energy must be removed in order to freeze.

Gas Laws I: What does Charles Law State

The volume of a gas is directly proportional to the temperature. V1/T1=V2/T2

Gas Laws II: What is the meaning of the term equivalent weight?

The weight of a substance which will react or produce 1 mol of Hydrogen. Also unit loss/gain of e- for redox reactions or 1 mol H+ for acid-base reactions.

Adipic Acid: Give two reasons activated charcoal is used in this experiment

To purify adipic acid by removing: fine carbon particles and brown color due to oxidized components

Density: After using the cord for the hot plate, one should return it to the front of the room where they got it

True

Gas Laws II: How many liters equal 1 equivalent of hydrogen at STP?

We have 1g-eq weight of hydrogen, which weighs 2.016g/mol, so we have 0.496mol. Therefore, we have a volume of 22.4 x 0.496 = 11.11L at STP.

Gas Laws I: What pressure units will you use on LoggerPro for this experiment?

mmHg

Determination of Ka of a Weak Acid: If HX represents the formula of a weak acid, what is the formula of the conjugate base of HX?

X-

Gas Laws I: How will you find the experimentally determined value for absolute zero.

Y will be temperature in degree Celsius. Plug in -273.15 for y since that is absolute zero and solve for x. X will be the y-int making x=0 then solving for absolute zero

Density: extensive property

a property that depends on the amount of matter in a sample

Density: intensive property

a property that depends on the type of matter in a sample, not the amount of matter

Types of reactions: Name two measurable properties that may change during a chemical reaction

conductivity temperature

Adipic Acid: Describe the crystals you obtained

crystals were colorless and resembled snowflakes

Density: What are the units of density?

g/cm3 g/mL

Conduct. & Grav. Det: What does the conductivity versus time graph look like? Where does equivalence point occur?

graph looks like a "V". Equivalence point occurs at the point where two lines intersect.

When does pH = pKa

half equivalence point

Conduct. & Grav. Det: define quantitative analysis

how many, uses numbers and figures, how much of particular compound or element

Conduct. & Grav. Det: define gravimetric determination

procedures that rely on weighing a substance

Adipic Acid: What are the uses of adipic acid?

synthesis of nylon food flavorings

Adipic Acid: Why do you heat the adipic acid solution?

to increase solubility

Adipic Acid: What is the purpose of this experiment?

to understand purification, recrystallization, solubilty and melting points

Conduct. & Grav. Det: What are units of conductivity?

uS/cm