Chem Lab Final Exam

Pataasin ang iyong marka sa homework at exams ngayon gamit ang Quizwiz!

g Cu in penny=

(measured g Cu/L) x (L of measured solution in volumetric flask)

In a single displacement reaction between a metal and an aqueous solution of a strong acid, such as Zn (s) + 2 HCl (aq) → ZnCl2 (aq) + H2 (g), gas bubbles are evidence of a reaction. If this is observed, Zn(s) was oxidized. What is the oxidation number of Zn in ZnCl2 (aq)?

+2

What function gave a linear plot with a positive slope in Experiment I (Lab 7)?

-1

H is ___ in compounds with metals or boron, and ___ in compounds with all other non-metals

-1, +1

A cold pack reached a temperature of 19.5 degrees Celsius starting from 23.0 degrees celsius. Assuming that the cold pack contained 200 mL of water, how much heat (qaq, Joules) was lost?

-2900 J

PdeltaV=

-w

The oxidation number of an atom in its elemental form is ___.

0

most acidic pH

0

the sum of oxidation numbers for the atoms of a neutral covalent or ionic compound is

0

Based on your answer to the previous question, how many moles of citric acid are in the 40.0 mL of 7-Up? Write your answer with the correct number of significant figures.

0.000423

If 25.31 mL of 0.0500 M NaOH solution are required to reach the equivalence point of an acid-base titration of 40.0 mL of 7-Up, how many moles of NaOH were required? Write your answer with the correct number of significant figures.

0.00127

R value

0.00821 atmxL/molxK

What is the concentration of Cu2+ (g/L) in the standard solution you will produce using 2.00 mL of the stock Cu2+ solution? (use correct sig figs)

0.200

What function gave a linear plot with a positive slope in Experiment II (Lab 7)?

1

What is the function that gave a linear plot with a positive slope in Experiment III (Lab 7)?

1

What is the function that gave a linear plot with a positive slope in Experiment IV (Lab 7)?

1

How many observable end points of citric acid will there be, and why?

1 because all 3 protons of the acid have similar strengths

What is the stoichiometry of the reaction between citric acid and sodium hydroxide?

1 mole of citric acid to 3 moles of sodium hydroxide

bond angle of tetrahedral

109.5

bond angle of trigonal planar

120

most basic pH

14

How many valence electrons are present in the CS2?

16

bond angle of linear

180

How many decimal points must be used to measure in a buret?

2 digits beyond the decimal point

In Part 4 (Lab 7), Avogadro's Law, your group will work with ___ other groups to collect the data needed, a total of ___ masses.

2, 6

What was the volume of soda required for Orange Crush and Jones Green Apple?

20 mL

How many moles of base are needed to completely neutralize one mole of citric acid?

3

In the acid base reaction of aqueous citric acid with aqueous sodium hydroxide. How many moles of base are needed to react with (neutralize) one mole of citric acid?

3

For Part 2, Gay-Lussac's Law, the initial water bath should be ~273 K. The temperature of the water bath is varied for each new reading by using ice and/or hot and cold tap water. The goal is to create ___ additional water baths that differ from each other and the original water bath by approximately ___ Kelvin.

4, 10

In Part 3 (Lab 7), Charles' Law, it is necessary to know the total volume (Vtotal, mL) of air in the apparatus which is the sum of the volumes of air in the bottle, the syringe and the tubing and connectors (Vtotal = Vbottle + Vsyringe + Vtubing). Vsyringe is recorded during the experiment, Vtubing is ___ mL, and Vbottle must be measured by disassembling the apparatus, filling the bottle with ___ , and measuring that volume using a 100-mL graduated cylinder.

4.0, water

What is the value of Vtubing?

4.0mL

What was the volume of soda required for Sprite and 7-Up?

40 mL

Including both rapid and accurate titrations, how many trials will you conduct in Part 1 (Traditional Titration Using an Indicator Dye)?

5

In Part 1 (Lab 7), Boyle's Law, the initial volume of the air in the syringe is set to ___ mL. For each reading, the volume of air in the syringe should be decreased by ___ mL.

55, 5

How many standard solutions were made in Experiment 9?

6

most neutral pH

7

At what pH range does phenolphthalein change color to pink?

8.2-9.2

At what pH does the end point occur for citric acid?

8.5

For the acid-base reaction of citric acid and sodium hydroxide, the equivalence point occurs at which pH?

8.5

bond angle of octahedral

90

bond angle of trigonal pyramidal

90 and 120

Which substance is reduced in the reaction: Mg (s) + 2AgNO3 (aq) -> Mg(NO3)2 (aq) + 2Ag (g)

Ag+ (aq)

Which substance is the reducing agent in the reaction: Mg (s) + 2AgNO3 (aq) -> Mg(NO3)2 (aq) + 2Ag (g)

Ag+ (aq)

silver nitrate

AgNO3

How do activity series work?

Any metal will replace any metal below it in the activity series, and a metal above HJ2 will replace H2 from an acid in aqueous solution

What is the molecular formula of citric acid?

C6H8O7

confidence interval equation

CI = mean ± SX.

example of dissolution of inorganic salt in water reaction

CaCl2 (s) -> Ca2+ (aq) + 2Cl- (aq)

Carbonated sodas (like Sprite or 7-Up) contain carbonic acid in addition to citric acid. Explain how it's possible that your reported results are only for the molarity of citric acid and do not include other acids present in sodas.

Carbonic acid is removed from the soda sample by making the soda go fat (decomposes to H2O and CO2) so it's not an acid seen in results from the titration. The other amounts of acids that are not citric acid are so small that they do not skew titration results when titrating for citric acid.

For Experiment 3 (Lab 7), ___ Law, the independent variable is temperature and the ___ variable is volume.

Charles', dependent

What is the more active metal in the equation, and why? Co (s) + 2HCl (aq) -> CoCL2 (aq) + H2 (g)

Co is more active than H2 because Co metal replaces H2 from the acid solution

copper and nitric acid equation

Cu (s) + 4HNO3 (aq) + 4H2O (l) -> Cu(H2O)6 (aq) + 2NO2 (g) + 2NO3- (aq)

What reactions had no reaction?

Cu (s) + MgSO4 (aq) Sn (s) + Zn(NO3)2 (aq) Cu (s) + HCl (aq) Cu (s) + SnCl2 (aq) Cu (s) + Zn(NO3)2 (aq) Zn (s) + MgSO4 (aq) Sn (s) + MgSO4 (aq)

Cu will not dissolve in acidic solutions because

Cu is less active than H2

cupric sulfate

CuSO4

You already know that Al is more active than Cu from the results of Experiment #4. Explain which reactions would be necessary to place metal in your current activity series?

Due to the fact that it is known that aluminum is more active than copper, it can also be implied that aluminum is more active than silver as well. In order to determine where aluminum falls on this activity series, it must undergo reactions with Mg, Zn, Sn, and H2.

Consider the reaction below: Pb (s) + Fe2+ (aq) → no reaction Which species is more active?

Fe

What does this mean? Fe (s) + Pb2+ (aq) -> Fe2+ + Pb (s) Pb (s) +Fe2+ (aq) -> no reaction

Fe is more active than Pb because Fe replaces Pb, but Pb does not replace Fe

Which substance is reduced in the reaction: Zn (s) + HCl (aq) -> ZnCl2 (aq) + H2 (g)

H+ (aq)

Which substance is the oxidizing agent in the reaction: Zn (s) + HCl (aq) -> ZnCl2 (aq) + H2 (g)

H+ (aq)

What is the equation for the flattening of soda?

H2CO3 (aq) -> H2O (l) + CO2 (g)

examples of neutral molecular ligands

H2O, H2S, CO, and NH3

Write the balanced reaction that shows the stoichiometry of the reaction.

H3C6H5O7 (aq) + 3NaOH (aq) -> 3H2O (l) + Na3C6H5O7 (aq)

enthalpy equation

H=E+PV

hydrochloric acid

HCl

acid-base reaction equation using hydrochloric acid and sodium hydroxide

HCl (aq) + NaOH (aq) -> H2O (l) + NaCl (aq)

nitric acid

HNO3

In a sentence each, describe the experimental method that was used to test the hypotheses in Experiments III and IV (Lab 7)

In experiment III, the number of moles and the pressure are kept constant, while the temperature varies and the volume is measured. In experiment IV, the temperature and volume are kept constant, while the number of moles varies and the pressure is measured.

Why must a colorless soda be used for the traditional titration method?

In rapid and accurate titrations, observations of color change are utilized through indicator dye. It is essential to be ablate see this color change to determine the desired moles. A colored solution wouldn't easily allow this to occur so a colorless solution would be used for an easier traditional titration method.

qaq units

J

qaq/mass of salt units

J/g

What temperature scale must be used to express the relationships between variables in the gas law experiments?

Kelvin

Which substance is oxidized in the reaction: Mg (s) + 2AgNO3 (aq) -> Mg(NO3)2 (aq) + 2Ag (g)

Mg (s)

Which substance is the oxidizing agent in the reaction: Mg (s) + 2AgNO3 (aq) -> Mg(NO3)2 (aq) + 2Ag (g)

Mg (s)

What was the activity series found in Experiment 6?

Mg>Zn>Sn>H2>Cu>Ag

What gases show nearly ideal gas behavior at ordinary temperatures and pressures?

N2, O2, H2, Ar (simple gases)

ammonia

NH3

moles of ___ reacted equals the moles of ___ produced (Experiment 7)

NaHCO3, CO2 gas

peroxide

O2 2-

examples of anionic ligands

OH-, CN-, and halide ions

Which soda or sodas cannot be titrated using the traditional (phenolphthalein) method?

Orange Crush and Jones Green Apple

What was k equal to in Experiment II (Lab 7)?

P/(T^n)

What was k equal to in Experiment I (Lab 7)?

P/(V^n)

ideal gas law equation

PV=nRT

Describe the physical behavior of an ideal gas.

Pressure, volume, temperature, number of moles are used to describe an ideal gas. One of the variables can be measured by measuring the other 3.

tin (II) chloride

SnCl2

standard deviation equation

Sx=((Σ (X-M)^2) /N)) ^(1/2)

molecular geometry of AX3E2

T-shaped

Explain the difference between the equivalence point and the end point of a titration.

The equivalence point is when the moles of the base are equal to the moles of the acid. The end point is an estimate of the equivalence point.

Explain the analytical method, a titration, in your own words. Include in your explanation the definition of the equivalence point.

The equivalence point occurs when the moles of the titrant are equal to the moles of the acid that were in the analyte. The stoichiometry, where in this case was 1 mole of citric acid per 3 moles of NaOH, allowed for the reaction to occur. With the known concentration of NaOH, the concentration of citric acid can be determined as well.

If the slope did not fall within the 95% confidence interval of k (for either Experiments I or II, Lab 7) briefly explain why.

There is no such thing as an ideal gas, it just shows the ideal behavior of a gas. The gas may not have showed the ideal behavior of a gas and therefore caused the slope to not fall within the confidence interval

m+

V x d

How do you calculate the volume of sodium hydroxide in Experiment 5?

Vf-Vi

What is the value of k for Experiment III (Lab 7)?

Vtotal/(T^n)

Vtotal equation for Experiment III, Lab 7

Vtotal=Vbottle+Vsyringe+Vtubing

mean equation

Xm=(Exi)/n

Briefly describe your experimental results for Experiment II (Lab 7). Did the results obtained support you hypothesis? If not, why?

Yes, the results supported my hypothesis. It was found that as temperature increases, the pressure increases.

Briefly describe your experimental results for Experiment I (Lab 7). Did the results obtained support you hypothesis? If not, why?

Yes, the results supported my hypothesis. It was found that as volume decreases, the pressure increases.

Which substance is oxidized in the reaction: Zn (s) + HCl (aq) -> ZnCl2 (aq) + H2 (g)

Zn (s)

Which substance is the reducing agent in the reaction: Zn (s) + HCl (aq) -> ZnCl2 (aq) + H2 (g)

Zn (s)

ligands

a molecule that binds specifically to a receptor site of another molecule

ligands always have

a pair of nonbonded electrons that are used to bond to the central metal ion

precipitation reaction

a precipitate is formed from materials that were originally dissolved in a solvent

oxidation-reduction reaction

a reaction that involves the transfer of electrons between reactants

Why couldn't the final temperature be measured in Experiment 8?

a small amount of heat is lost from the calorimeter

titrant

a solution of known concentration

chemical reaction

a substance is converted into a different substance

caustic

able to burn or corrode organic tissue by chemical action

Was absorbance or transmittance more useful in Experiment 9?

absorbance

A UV-vis spectrophotometer is an instrument that measures how much light energy, of a particular wavelength, is ___ by a sample placed in the light beam of the instrument. The instrument will be used to measure the absorbance of known concentrations of solutions containing the copper complex ion. These are called ___ solutions and will produce a linear calibration curve. These six solutions are prepared by diluting a Cu2+ stock solution of ___ g/L.

absorbed, standard, 5.00

What reaction is utilized in an acid-base titration?

acid-base reaction

What reaction occurs when Alka Seltzer tablets are dissolved in water?

acid-base reaction

For polyatomic ions, the total number of valence electrons must be adjusted for the charge of the ion. ___ one electron for each negative charge and ___ one electron for each positive charge.

add, subtract

What is the purpose of citric acid in carbonated beverages?

adds tartness

What were sources of error associated with the use of a buret?

air bubbles trapped in the stopcock or buret tip, not reading the buret volume at eye level, and over or underestimating the end point color

In the last gas law experiment (the fourth one), the gas sample is not ___ like in the first three. The gas sample for the fourth experiment is ___.

air, carbon dioxide

How is carbonic acid removed from the soda?

allowing the soda to go flat

The H2O ligands can be replaced by ___ to generate complex ions

ammonia (NH3)

During the experiment, when ___ (NH3) is added to the solution of dissolved Cu and Zn, the solution will turn a deep ___ color. The species responsible for this color is [Cu(NH3)4(H2O)2]2+.

ammonia, blue

specific heat capacity

amount of heat required to raise the temperature of 1 gram of the material by 1 K

polyprotic acid

an acid that can donate more than one proton per molecule

monoprotic acid

an acid that can donate only one proton per molecule

net ionic equation

an equation for a reaction in solution showing only those particles that are directly involved in the chemical change

What does an independent variable mean in terms of gases?

any one of the variables can be determined by measuring the other 3

What do Alka Seltzer tablets contain?

aspirin, citric acid, and sodium bicarbonate

What was the unit for k in Experiment I (Lab 7)?

atm/(L^-1)

What was the unit for k in Experiment II (Lab 7)?

atm/K

molecular geometry of AX2E

bent

molecular geometry of AX2E2

bent

Your group will need to calibrate the spectrophotometer during the experiment. Which standard solution will be used?

blank solution

Which device is used to both deliver and measure the volume of sodium hydroxide (NaOH) to the citric acid solution?

buret

What were the solutions utilized in Experiment 8?

calcium chloride, sodium chloride, ammonium nitrate, potassium chloride, lithium chloride, potassium nitrate, sodium bromide, ammonium chloride, sodium nitrate, and magnesium chloride

sodium hydroxide is ___

caustic

in the complex ion Cu(H2O)6 2+, Cu2+ is the ___ ___ ___and ___ ___ ___ are covalently bonded giving the species an overall ___ charge

central metal ion, 6 H2O molecules

complex ion

charged species consisting of metal ion surrounded by ligands

What is a common acid present in carbonated beverages?

citric acid

Observations are a very important part of this experiment. Make two tables in your lab notebook: one small table that summarizes positive and negative evidence for reactions and one ___ table (use one whole notebook page) for your observations. Examples of observations include: ___ changes, solid formation or dissolution, gas formation and whether the reaction was slow or fast.

color

What physical changes should have been recorded in your notebook in Experiment 6?

color changes, solid formation, solid dissolution, gas formation, and whether the reaction is slow or vigorous

(Zn(NH3)4(H2O)2)2+ is

colorless

What must be a characteristic of a solution being titrated traditionally?

colorless

examples of redox reactions

combination reactions, decomposition reactions, and displacement reactions

What other chemical was used in Experiment 9?

concentrated ammonia

The absorption of light energy by a molecular species can be of use for quantitative analysis because the amount of light energy absorbed at a particular wavelength by a compound in solution is proportional to its ___ in that solution.

concentration

absorbance is directly proportional to

concentration

How do you calculate the moles of NaOH in Experiment 5?

convert VNaOH from mL to L, then utilize the known concentration to determine the number of moles present in the sample

How do you calculate the molarity of citric acid in Experiment 5?

convert the Vsoda to L and then divide the moles of citric acid by the volume of soda

if the reaction is endothermic, the temperature of the surrounding medium would

decrease

endothermic calibration curve

decreases then increases

(Cu(NH3)4(H2O)2)2+ is

deep blue in color

T units for Experiment 8

degrees Celsius

change in enthalpy equation at constant pressure

deltaH=deltaE+PdeltaV

change in enthalpy in regards to qp

deltaH=qp

d

density

A single displacement reaction in which a metal displaces a second metal in a solution of the second metal ion establishes the relative reactivity of the two metals as reduction agents. Evidence of this type of reaction typically includes a color change in the solution and/or ___ of the displaced metal on the surface of the reactive metal.

deposition

How do you calculate the moles of citric acid in Experiment 5?

divide the number of sodium hydroxide by 3

oxidizing agent

electron acceptor, the substance being reduced

reducing agent

electron donor, the substance that is oxidized

In this experiment, you will assign formal charges to individual atoms in your Lewis structures. A handy equation: F.C. = number of valence ___ in the ___ atom - (number of non bonded electrons + 1/2 x number of ___ electrons)

electrons, neutral, bonding

What is the estimate of the equivalence point called?

end point

In thermodynamics, chemists define a system. When a reaction takes place in aqueous solution, the solvent, water, is part of the surroundings. If a reaction (system) loses heat, that heat is gained by the surroundings. If a reaction gains heat, that heat is removed from the surroundings. If the temperature of the water decreases when a reaction takes place in aqueous solution, the reaction was ___.

endothermic

if the reaction removes heat from the surroundings, the reaction is

endothermic

In an experiment, a student measured the initial temperature of 100.0 mL of water to be 22.0oC. By graphical analysis, they found Tf = 16.1oC. Based on the change in temperature, is this an exothermic or endothermic reaction? Calculate the heat absorbed or lost by the aqueous solution, qaq, in Joules (J) assuming that the specific heat capacity of water is 4.18 J/g∙K. Consider significant figures in your answer.

endothermic, -2500 J

H

enthalpy

In an acid-base titration, the ___ ___ occurs when the number of moles of acid is stoichiometrically equal to the number of moles of base added to neutralize the acid.

equivalence point

Due to the equivalence point being difficult to measure in laboratory, scientists typically

estimate the equivalence point by using an indicator dye to signal that the amount of titrant added is equal to the analyte in a sample

Part 1 of the experiment involves qualitative heat studies. You will determine if a particular reaction is endothermic or exothermic by touching the outside of the reaction test tube after a salt is dissolved in water. If the test tube gets warmer upon the dissolution of the salt, the reaction was ___.

exothermic

In the data analysis of the quantitative studies you will graph your data using Logger Pro. The initial temperature (Ti) is the temperature at time 0 seconds. The final temperature (Tf) cannot be measured directly and must be obtained by ___ to time zero.

extrapolation

How were the slopes determined in Experiment I & II (Lab 7)?

from the graph

molar mass units

g/mol

reduction

gain of electrons

R

gas constant

each of the relationships that exist between variables are called

gas laws

What should be worn in lab for Experiment 8?

goggles and gloves

mass units

grams

∆H = qp where ∆H is the change in enthalpy and qp is the ___ gained or lost by a system at constant pressure.

heat

qp

heat gained or lost by a system at constant pressure

If qp<0,

heat is lost by the system to the reaction

the reaction would be exothermic if

heat is lost to the surroundings

What solutions are corrosive to the skin and eyes in Experiment 6?

hydrochloric acid and silver nitrate

What solutions are toxic when swallowed or inhaled in Experiment 6?

hydrochloric acid, tin (II) chloride, cupric sulfate, and silver nitrate

Once you have completed all of the reactions in Experiment 6, you will be able to list the metals and ___ in order of decreasing reactivity as reducing agents (or decreasing ease of oxidation) to make up an abbreviated activity series. An activity series is useful tool because it allows one to make predictions regarding metal displacement reactions without having to actually conduct the experiments.

hydrogen

What is an acid-base reaction?

hydrogen ion is transferred from an acid to a base

What is an absorption spectrum of a molecule used for?

identification

How did you dispose of the waste in Experiment 9?

in the labeled containers in the fume hood

Assuming the number of moles and pressure of a gas are kept constant, when the temperature of a gas is increased, I expect the volume of a gas to

increase

Assuming the number of moles and temperature of a gas are kept constant, when the volume of a gas is decreased, I expect the pressure of the gas to

increase

Assuming the number of moles and volume of a gas are kept constant, when the temperature of a gas is increased, I expect the pressure of the gas to

increase

Assuming the temperature and volume of a gas are kept constant, when the number of moles of a gas is increased, I expect the gas to

increase

exothermic calibration curve

increases then decreases

How can you describe the four variables that describe the physical properties of a gas?

independent

Double or triple bonds are used to connect atoms when there are ___ valence electrons remaining to complete the octets of all atoms. Only elements of the ___ period or higher on the periodic table may exceed the octet rule in some of their structures.

insufficient, third

This lab will make use of a calorimeter to measure the amount of heat given off or absorbed by a reaction. The calorimeter needs to be well- ____ in order to obtain ____ measurements; this is why ___ polystyrene coffee cups are used.

insulated, accurate, 2

E

internal energy of a system

Outside of lab, students will use the equation of the line from the calibration curve and the absorbance values for each penny solution from the group to ___ the concentration of Cu (g/L) in each penny sample from the group. If you need help with this process in lab, see Chapter 3 (Expt #1) or Chapter 5 (Expt #3).

interpolate

Why is citric acid present in much higher concentrations than other acids (other than carbonic acid)?

it adds flavor

What is produced the nitric acid reacts with metals?

it produces a poisonous brown gas called NO2

Why was magnesium the most active metal in the activity series?

it replaced the metals found in HCl, CuSO4, SnCl2, AgNO3, and Zn(NO3)2

What happens when NO2 reacts with your skin?

it turns your skin yellow/brown

Why was silver the most active metal in the activity series?

it was replaced by said metal in every tested situation

deltaHsoln units

kJ/mol

election pair arrangement of AX2

linear

molecular geometry of AX2

linear

molecular geometry of AX2E3

linear

oxidation

loss of electrons

What was the most active metal in the activity series found in Experiment 6?

magnesium

example of exothermic salt used in Experiment 8

magnesium chloride

What method do acid-base titrations rely on to observe titrations?

measuring the pH of the solution

How can the value of R be obtained?

measuring the volume, temperature, and pressure of a given amount of gas and substituting the values in the ideal gas equation

buret volume

meniscus

units of molarity

mol/L

For Experiment 4 (Lab 7), Avogadro's Law, the independent variable is ___ and the dependent variable is pressure.

moles

Hydrochloric acid is an example of what type of acid?

monoprotic acid

How do you determine the concentration of Cu2+ in each of the standard solutions?

multiply the concentration of the stock solution by the measured volume, and divide it by the final diluted volume

The following redox reaction is written as a balanced molecular equation: 2Fe (s) + 6HNO3 (aq) → 2Fe(NO3)3 (aq) + 3H2 (g) What is the spectator ion for this reaction?

nitrate

In Experiment #6 you learned that Zn will dissolve in acidic aqueous solutions as Zn2+, but Cu will not dissolve because Cu is less active than H2. A stronger oxidizing agent than H+ is required to oxidize Cu. Aqueous solutions of ___ are strong oxidizing agents that are capable of oxidizing a number of less active metals, including Cu.

nitric acid

The oxidation of both Cu and Zn (both present in a penny) with nitric acid generates complex ions of Cu and Zn in solution. It also produces ___ , a brown, toxic gas. For this reason the dissolving of the penny must be carried out in the ___ .

nitrogen dioxide, fume hood

What gases are in the air we breathe?

nitrogen, oxygen, argon, carbon dioxide, and water vapor

Do ideal gases exist?

no

If a metal is less active than H2, ___ ___ will occur when the metal is added to a strong acid.

no reaction

Can the three reactions between each 3 of the acidic protons and the base be distinguished from each other?

no, because the 3 acidic protons are of similar strength and all react with a base to a similar extent

Are there any hazardous chemicals used in this experiment?

no, but goggles must be worn at all times

This experiment will be done in two parts. Before beginning either part, each student must write two hypotheses in their ___ by completing the sentences that are given before the procedure. These hypotheses are written by using the ___ to predict how the two coupled variables will vary with each other in an experiment in which the other two variables are held constant.

notebook, ideal gas law

equivalence point

number of moles of base added is stoichiometrically equal to the number of moles of acid originally present in the analyte.

What is a qualitative determination of whether a reaction is endothermic or exothermic?

observing whether the temperature goes up or down during a reaction

electron pair arrangement of AX4E2

octahedral

electron pair arrangement of AX5E

octahedral

electron pair arrangement of AX6

octahedral

molecular geometry of AX6

octahedral

After connecting the atoms, complete the ___ of atoms by adding nonbonded lone pairs to each, beginning with the most ___ atoms. Be sure not to use more electrons than are available!

octets, electronegative

Does the end point underestimate or overestimate the equivalence point?

overestimates slightly

Any titration requires that the reaction be monitored to determine when the equivalence point has been reached. For acid-base titrations and the experiment you will conduct, the most common methods rely on measuring the:

pH

The pH can be directly measured with a

pH electrode

equation for pH

pH=-log[H+]

What kind of error will result from not reading the buret volume at eye level?

parallax error

When is the oxidation number for oxygen -1?

peroxides

What is the most common indicator dye use for titrations of strong acids and strong bases?

phenolphthalein

Citric acid is an example of what type of acid?

polyprotic acid

How do you dispose of the solutions used in Experiment 8?

poured doen the drain

P

pressure

Which 4 variables can the physical behavior of a gas be described by?

pressure, volume, temperature, and number of moles

heat absorption equation

q=Cs x m x (Tf-Ti)

If deltaH<0,

qp is also <0

What type of analysis was required to find the metal content in the coins?

quantitative

In Part 2 of the experiment, you will do ___ heat studies. The device you will use to conduct these studies is a calorimeter. You will conduct ___ total trials in Part 2.

quantitative, 4

acid-base reaction

reaction involving the transfer of a hydrogen ion between reactant species

A substance that is oxidized (loses electrons) causes a reduction and is therefore called a ___.

reducing agent

if deltaH<0, the reaction would

remove heat from the surroundings

molecular geometry of AX4E

seesaw

total ionic equation

shows all soluble ionic substances dissociated into ions

molecular equation

shows the complete formulas of all reactants and products

What was the least active metal in the activity series found in Experiment 6?

silver

After counting the number of valence electrons, the atoms of the molecule or polyatomic ion should be written/drawn to show the correct connectivity, using ___ bonds to connect adjacent atoms.

single

What type of redox reaction was the focus of Experiment 6?

single-displacement reactions

Why was the Alka Seltzer tablet dissolved in acetic acid rather than water?

so that we can observe an increased amount of gas in our experiment

NaHCO3

sodium bicarbonate

example of endothermic salt used in Experiment 8

sodium nitrate

Are the inorganic salts toxic and/or irritating to the skin in Experiment 8?

some are, but you should treat them the all the same way and avoid contact with these materials

When carrying out a chemical reaction in aqueous solution, you can easily monitor the temperature of the water (surroundings). By noting the change in temperature (Tf - Ti), you can calculate the amount of heat (q) that was either lost or gained by the water. To do this, you must also know the mass (m) of the water, and the ___ (Cs) of water. The equation is: q = Cs∙m∙(Tf - Ti)

specific heat capacity

molecular geometry of AX4E2

square planar

molecular geometry of AX5E

square pyramidal

What is nitric acid?

strong acid and powerful oxidizing agent

analyte

substance being measured

microscope laboratory techniques

techniques must involve much smaller volumes of solutions that allow you to carry out the experiments quickly and safely without a lot of waste

For Experiment 2 (Lab 7), Gay-Lussac's Law, the independent variable is ___ and the dependent variable is ___.

temperature, pressure

electron pair arrangement of AX2E2

tetrahedral

electron pair arrangement of AX3E

tetrahedral

electron pair arrangement of AX4

tetrahedral

molecular geometry of AX4

tetrahedral

How was the 1982 penny different than the current penny?

the 1982 penny had 95% copper while the current penny has 2.5% copper by mass

transmittance

the ability of light to pass through a medium

Why were two polystyrene cups used in Experiment 8?

the air space between the cups provided extra insulation

After the removal of carbonic acid, there are small amounts of other acids present. How can the amount of citric acid be determined?

the amount of citric acid can be quantitatively determined by an acid-base titration because of large differences in the concentrations

Why was is necessary to find Tf using Logger Pro by extrapolating back to time=0 seconds?

the calorimeter releases small amounts of heat so the final temperature cannot be truly recorded, so the final stable points were made into a linear fit and the final temperature was found

quantitative analysis of the coins required for

the coins to be dissolved

Why is it important that these reactions are run in 2 polystyrene cups nestled in a beaker (instead of only a beaker)?

the cups allow for heat to be kept within the system due to the insulation provided by the cups, which reduces heat loss

Which reactions were used in Experiment 8?

the dissolution of an inorganic salt in water

Where are the solutions disposed of in Experiment 6?

the fume hood

enthalpy

the heat content of a system

Where will the estimate of the equivalence point be on a graph of a modern titration?

the point of most rapid pH change

oxidation number

the positive or negative charge of a monatomic ion

if there was increase in temperature of the surrounding medium,

the reaction would be exothermic

The experiment you will perform seeks to establish what?

the relative chemical reactivity of several metals and hydrogen and reducing agents

How was the heat lost from the calorimeter corrected?

the solution temperature is measured over a period of time after mixing reactants and Tf is obtained by extrapolation back to time zero

if heat is lost to the surroundings,

the temperature of the medium would increase

The pH can me indirectly measured by

the use of an indicator dye that changes color at the desired pH

What do you do if you spill NaOH on your skin or clothing?

thoroughly rinse the affected area with water for 15 minutes

Using a solution of known concentration to determine the concentration of another solution through a monitored reaction of known stoichiometry that goes to completion is called a ___.

titration

Why is it important to record your observations of each reaction in your notebook in Experiment 6?

to determine whether a reaction took place or not

What were the objectives of Experiment 6?

to explore and compare the relative reactivity as reducing agents of several metals and hydrogen, use microscope techniques to evaluate a series of possible reactions between solid metals and dissolved cations in aqueous solution, develop a limited activity series for a group of metals based on experimental data, and write balanced molecular, total ionic, and net ionic equations for displacement reactions

What were the objectives of Experiment 10?

to learn how to draw Lewis structures of molecular species, use the Lewis structures of molecular species and VSEPR theory to predict their 3D geometry, use the predicted molecular model kit to generate 3D molecular models of molecular structures, and learn to represent 3D structures with 2D drawings

List two objectives of Experiment 5.

to learn how to perform initial rapid titrations as well as accurate titrations, and to calculate citric acid molarity in sodas

What were the objectives of Experiment 7?

to learn how to perform simple gas phase experiments involving the measurement of volume, temperature, and pressure, develop hypotheses about the pair-wise relationships of 4 variables in the ideal gas law, and experimentally test these hypotheses

What were the objectives of Experiment 9?

to learn how visible and UV absorbance of a compound in solution is related to its concentration, learn how to use a UV-visible spectrophotometer, prepare and utilize a calibration curve based on the Beer-Lambert law, learn about oxidation of less active metals and complex ion formation, and experimentally determine the amount of copper in a penny using the absorbance characteristics of the complex ion Cu(NH3)42+

What were the objectives for Experiment 8?

to understand the concept of enthalpy, understand how deltaH is related to temperature changes during a reaction, learn to use calorimetry to experimentally determine deltaH, and learn to use thermodynamic data for practical applications

What were the objectives for Experiment 5?

to understand the difference between polyphonic and monoprotic acids, learn the basics of the pH scale, learn how to perform an acid-base titration, compare and contrast two methods for detection of the estimated equivalence point of an acid-base titration, and calculate the molarity of citric acid in two sodas

What were the two methods for detection of the estimated equivalence point of an acid-base titration?

traditional indicator dye and modern pH electrode

In oxidation-reduction (redox) reactions, there is a net ___ of electrons from one reactant to another.

transfer

electron pair arrangement of AX2E3

trigonal bipyramidal

electron pair arrangement of AX3E2

trigonal bipyramidal

electron pair arrangement of AX4E

trigonal bipyramidal

electron pair arrangement of AX5

trigonal bipyramidal

molecular geometry of AX5

trigonal bipyramidal

electron pair arrangement of AX2E

trigonal planar

electron pair arrangement of AX3

trigonal planar

molecular geometry of AX3

trigonal planar

molecular geometry of AX3E

trigonal pyramidal

What is the more specific term for what type of acid citric acid is?

triprotic acid

What is a quantitative determination of whether a reaction is endothermic or exothermic?

use of a calorimeter which can directly measure the amount of heat given off or absorbed by the reaction

Lewis structures are a simple shorthand representation of the bonding of atoms and the distribution of ___ electrons in molecules and polyatomic ions of the main-group elements.

valence

V

volume

What kind of error will result from air bubbles trapped in the stopcock or buret tip?

volume dispensed

What kind of error will result from over or underestimating the end point color?

volume dispensed

For Experiment 1 (Lab 7), Boyle's Law, the independent variable is ___ and dependent variable is ___.

volume, pressure

What is the medium that the calorimeter used to absorb or lose heat?

water

In Experiment III and IV, it may have been more difficult to get a good linear fit of the data in comparison to Experiments I and II. Give one example of an experimental difficulty that may have led to a lower correlation.

water in the bottle or leakage of pressure

How do you handle HNO3?

wear gloves, goggles, and work in a fume hood when dissolving the penny in nitric acid

salt solutions in Experiment 8 that are spilled on your gloves

will be deposited on anything you touch

-w

work done by the system

Because there is trial and error involved in writing Lewis Structures, you should initially work out each problem in your lab notebook and then transfer the correct answers to the ___ in pen.

worksheets

Do all gases have similar properties?

yes

change in energy equation

ΔE=qp+w


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