Chem Lab Final Exam
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
