The chemistry of carbon and its compounds is called organic chemistry.
Carbon and hydrogen atoms are the organic compounds of hydrocarbons.
There are only single bonds in alkanes.
Alkanes are named in a systematic way. The rules for naming alkanes should be reviewed.
There are compounds that have the same formulas but different ones. The various structural isomers of alkanes should be reviewed.
A functional group is a group of atoms. The general functional groups should be reviewed.
There are millions of macromolecules.
Macromolecules are composed of repeating units.
There will be a question concerning an experiment in the free-response portion of the AP exam. The basic experiments that the AP Exam Committee believes to be important are reviewed in this chapter. You should pay particular attention to the experiments that you did not perform in this chapter. You may find that you did a similar experiment after reading the description. Every AP class has at least one experiment that may appear on the AP exam.
The equipment, measurements, and calculations required have been the subject of the free-response questions. Sources of error can be considered in some cases. You will need an understanding of the chemical concepts involved to answer the question completely.
To discuss an experiment, you need to be familiar with the equipment.
There is a complete list of equipment for the experiments in the beginning of the chapter. You need to be familiar with each item. You may need to talk to your teacher if you know an item by a different name.
In some cases, the exam question will request a list of equipment you need, while in other cases you will get a list from which to choose the items you need.
There are items in many experiments. The analytical balance, beakers, support stands, pipets, test tubes, and Erlenmeyer flasks are included. Burets, graduated cylinders, desiccators, drying ovens, pH meters, volumetric flasks, and thermometers are also commonly used. These are good guesses if you don't know what you want. Three or fewer experiments are where most of the remaining equipment appears.
You will need to know the basics for the experiment.
You might need to measure the initial and final temperatures. Don't say you measure the change in temperature. Students lose exam points for not differentiating between measured and calculated values.
There are two categories for the basic calculations. Simple calculations, such as the change in temperature or volume, are easy to forget. Mass-to-mole conversions can also be included in simple calculations. Values are usually entered into one of the equations given at the beginning of the previous chapters.
The individual experiments have specific equations in the chapters.
Specific experiments that are performed in this investigation are an introduction to the field. They are designed to show the relationship between the amount of light absorbed by some solutions and their concentrations. Light from a specific wavelength is passed through a sample. The amount of light transmitted by the solvent is subtracted from the amount of light transmitted by the sample.
The concentration of an unknown solution could be determined by using this relationship.
To measure the transmittance of the solution, you have to subtract the transmittance of the solvent and then measure it.
Plot the molarity of the different solutions versus the transmittance to determine the relationship between the concentration of the solution and the transmit tance. The formula Abs is used to calculate the absorbance of the solution, while the formula T is used to calculate the transmittance of the solution. You can read absorbance directly on a SPEC 20.
If you are asked for the mass of the solute in the unknown, you use your data to determine its molar concentration. The grams of solute present in the sample can be calculated using the molar concentration, volume, and mass of the solute.
Specific experiments that are performed in this investigation use the concepts and tech niques developed in Experiment 1 Spectroscopy in order to determine the mass percentage of a particular substance in a solid sample. The amount of copper in a brass sample is one of the things that can be determined in an experiment. The best wavelength to use is determined first. The maximum absorbance of the chemical species being determined is given by the best wavelength. The solutions of the solute being determined are then measured using a spectrophotometer. A plot of absorbance versus concentration is prepared. The sample is dissolved in water. A portion of the sample is measured and its concentration determined using a graph. The mass of the substance can be found from this information. The mass percentage of the substance in the sample can be calculated using this mass information and the mass of the sample.
The absorbance of one of the stock solutions can be measured using a spectrophotometer. The data of absorbance versus wavelength is plotted, and the wavelength that gives the maximum absorbance is chosen to be used for the rest of the experiment. Each dilution's absorbance is measured. A plot of absorbance versus concentration is prepared either by hand or using a spreadsheet. If it is copper, the sample needs to be dissolved and thenDiluted to a certain volume. Beer's law plot is used to determine the concentration of that solution. The moles and grams of the substance can be calculated using the concentration and volume of the solution. The mass percentage of the sub stance can be calculated using the initial mass of the sample.
The brass will be dissolved in concentrated nitric acid if you are doing a brass analysis. The NO gas that is produced is toxic. If you are describing the process on the AP exam, be sure to stress safety.
Determination of the mass of a specific substance in a sample by precipitation, drying, and weighing is one of the specific experiments that are performed in this investigation. A common experiment done in this category is the determination of the water's hardness. The amount of calcium, magnesium, and iron in the solution affects the water sample's hardness. The carbonate salts may be precipitated. For simplicity's sake, hard- water samples are usually prepared with only one of these ion. The carbonate salt is dried in a drying oven after being separated from the solution. The mass of the dry salt is determined and the water sample hardness is calculated.
Mass and volume determinations will be made by the student.
The grams of calcium carbonate per liter of water sample are first calculated. The calcium carbonate per liter of water sample is converted using appropriate conversions.
Mass and volume measurements must be done accurately.
In the titration procedure, the concentration of an acid is determined by adding small quantities at a time of a base of known concentration until the point at which the moles of base equal the moles of acid present. Adding a small amount of acid to a base solution can be used to determine the concentration of the base solution. An indicator or a pH meter can be used to deter mined neutralization points. The point at which a color change happens with the indicator is called the endpoint of the titration. You can calculate the concentration of the unknown acid by knowing the volume of the acid and the number of liters it took to reach the endpoint. The acid of known concentration can be used to determine the concentration of an unknown base.
The unknown acid solution will be placed into the Erlenmeyer flask with a pipet. The buret will be filled with acid.
The indicator will change color when you add small amounts of base drop. The final volume reading is the volume of base added.
The concentration of the base is calculated using a reaction.
The moles of base can be calculated from the molarity of the base and the volume used. The moles of acid will be caused by the1:1 stoichiometry. The acid's molarity is determined by the liters of acid solution pipetted into the flask.
The type of titration can be done without an indicator. The volume will be plotted against the pH readings. The point of the curve is the endpoint. A titration can be used to determine the acid content of household substances such as fruit juices or sodas.
Simple physical means can't separate the components in a solution. This is true of polar solutes because of their interactions. One method that is often used is chromatography. A small amount of solu tion is spotted on a strip of paper and allowed to dry.
The jar contains a small amount of solvent.
As the solvent moves up the strip the different solutes can be separated. Sometimes the choice of the solvent must be done by trial and error.
The student will measure the distance that each component traveled and the distance that the solvent traveled.
The Rf value is determined by the calculations. The distance the component travels is divided by the distance the solvent traveled. Substances that interact strongly with the paper do not travel very far, while those that interact strongly with the solvent travel much farther.
A powerful separation technique is chortography.
The student is given a set of bottles with different types of bonding in them. To determine the bonding type, you need to score high chemical tests. The tests might include melting point.
Solid nonmetals have a dull luster.
covalent compounds have lower melting points than ionized compounds.
Water is generally insoluble or slightly insoluble in ion compounds and polar covalent solids.
Aqueous solutions of ionic compounds are conductors.
There are no calculations associated with this experiment.
There are many other tests that could be used.
You are asked to verify the results of an experiment by checking both the procedure and the calculations. You will be asked to figure out the percent by mass of the substances. The unique properties of the components in this mixture will be used to make this happen.
A sample mixture is heated and weighed.
The mass of CO2 and H2O is lost. The ratio of moles of water and carbon dioxide is shown in the equation for the decomposition reaction.
To increase the accuracy of the determination, several runs should be made and an average taken. This procedure can be applied to many other reactions. A titration procedure could be used to analyze these samples.
The concentration of a substance will be determined in this experiment. Before it can be used in the titration, it needs to be standardized.
The goal of the titration is to analyze the commercial hydrogen peroxide that can be found in a pharmacy. The Fe(NH4)2(SO4)2*6H2O solution can be standardized against the KMnO4 solution. A standard solution of Fe(NH4)2(SO4)2*6H2O, a sulfuric acid solution, and a solution of potassium permanganate will be prepared.
You will be measuring the mass of Fe(NH4)2(SO4)2*6H2O and the KMnO4 and many volumes of the pipets, volumetric flasks, and the buret.
The number of grams of Fe(NH4)2(SO4)2*6H2O used can be used to calculate the moles of Fe2+.
The overall reaction is composed of 1 MnO4 and 5 Fe2+.
The moles of hydrogen peroxide can be calculated from the buret volume and the molarity of the KMnO4 solution. You can get grams and mass percent from the moles.
You should be very careful in making your measurements. There is a general procedure that can be applied to other systems.
The chemical and physical properties of the mixture components are used in this experiment. This is the basis of the analy sis of commercially available samples. The binder can be separated by the difference in their solubility in water and organic acids, their acidity, and the way they react with hydrochloric acid and sodium bicarbonate solutions.
Every time a component is separated from a solid, it is dried and the mass determined.
You should be very careful in making your measurements. There is a general procedure that can be applied to other systems.
When handling acid solutions, be careful. Vent the separatory funnel before opening it.
The factors involved in the speed of a chemical reaction will be explored in this experiment. The experiment focuses on the decomposition of calcium carbonate. There are pieces of calcium carbonate of dif ferent sizes that can be used to test the speed of reaction. The temperature of the mixture can be changed by using an ice bath or heating it. In order to measure the speed of the reaction, the carbon dioxide gas product can be collected in a syringe, or a gas pressure probe can be used to monitor the production of the CO2(g) as a function of time. The mass of sample consumed can be used as an indication of the speed of reaction.
The initial and final mass of the calcium carbonate sample are measured.
The mass of sample lost is a function of time. The mass versus time results are plotted.
The time is the horizontal axis, while the mass lost is the vertical axis.
When handling hydrochloric acid, be careful.
The rate law will be determined in this experiment.
The reaction of crystal violet with NaOH is a common one. The progress of the reaction is followed by a colorimeter. The Beer's law calibration curve will be created by measuring the Absor bance of solutions of crystal violet.
You will be measuring absorbance and time. It's important to use a blank that only contains water and NaOH.
When handling the solution, be careful.
In this experiment, you will be measuring the heat produced during the dissolving of vari ous ionic substances in water with the goal of determining which of the salts is most efficient in generating heat. Substances that could be tested include anhydrous calcium chloride (CaCl2), anhydrous sodium carbonate (Na2CO3), anhydrous ammonia nitrate (NH4NO3), and similar salts. You might be using a magnetic stirrer instead of the stirring wire shown in the figure.
You will be measuring the initial and final temperatures of the solutions formed by adding a mass of solute to a measured amount of water.
The strong oxidizer is the ammonium nitrate.
Experiments that fall into this category examine systems that are at equilibrium. A lot of times this involves having a small tray of reagents and testing an equilibrium system by mixing selected reagents and making obser vations. You can add more reagent or change the temperature of the solutions. An acid-base equilibrium or complex ion equilibrium may be involved.
You should be able to describe how the system reacted to the stress that you imposed.
This experiment only involves the estimation of volumes and mass.
This experiment does not involve calculations.
When working with concentrated ammonia and hydrochloric acid, be careful. Keep reagents in the hood and wear goggles, gloves, and an apron.
Acid-base titrations involving weak acids or weak bases are Experiments that fall into this category. The equivalence point is determined graphically after the course of the titration is followed by a pH meter. Both monoprotic and polyprotic acids can be tested. You should be able to determine whether the solution at the equivalence point will be basic or acidic by examining the specific reaction involving a weak acid or base.
You will be measuring the pH and Plotting them against the volume of titrant added.
In many cases, you will use a NaOH solution to measure the strength of acids. The point of inflection of the curve is the point at which a dramatic increase in pH occurs. The same is true of bases, except the pH will be decreasing during the titration.
Wear all of your personal protective equipment when working with acids and bases. Adding acid to water is not the same as adding acid to acid.
A buffer is a substance that resists a change in pH. A mixture of a weak acid and its conjugate base is what it is. Experiments in this category look at the properties of household substances that are buffers. This will involve adding acid or base to a substance and following the course of titration with a pH meter to plot the pH versus mL of the added acid or base. There is a buffer present at any point before the equivalence point. Household substances can be tested for their buffer ability. The curve of pH versus mL of a substance that has buffering ability rises sharply initially and then levels off much more than a titration of a substance that is not a buffer. This can be used to determine if an unknown solution has buffering capability.
You will be measuring volume and pH for a wide range of substances. The point of maximum buffering is the point halfway to the equivalence point.
The acid and base solutions need to be handled with care.
The capacity of a buffer is the amount of acid or base that can be mitigated by the buffer. You can determine this by using different amounts of the conjugate acid and base components, or by changing the concentration of each by the same amount. The higher the concentration of the conjugate acid and base in the buffer, the more moles of added base or acid can be neutralized. The buffer of a specific pH will be created by you.
You will be measuring volume and pH for a wide range of substances. You will be making graphs of the two variables.
Wear all of your personal protective equipment when working with acids and bases. Adding acid to water is not the same as adding acid to acid.
The moles are not weighed using an analytical balance.
To practice for the AP Chemistry exam, use these questions to review the content of this chapter. There are 10 multiple-choice questions that are similar to what you will see in the chemistry section of the exam. Section II of the exam has a long free-response question. You can make these questions even more authentic by following the instructions.
You can't use a calculator. The periodic table and equation sheet can be found at the back of the book.
You have a solution of sugar.
A chemist makes a solution by dissolving 10 g of the simplest method to separate the sugar from the urea in 100 g of water.
A chemistry student adds urea.
She needs the density of water and the den of the procedures he should use to solve the problem.
The units of the solution are listed.
A chemistry student prepares a solution of an unknown solid.
She dissolved 2.50 g of the unknown substance in 100.0 g of water.
Questions 6 and 7 can be used with the following diagram.
A student is trying to make a cell that can produce 1.23 V.
The voltage is perfect.
The voltage becomes zero when volume strong acid is added.
The idealized titration is greater than ideal.
The composition of the sample will affect the composition of the cell.
The cell voltage is measured by her.
A sample of pure sodium oxalate was used in a trial run.
A chemist constructs a linear graph.
Separating materials from solution involves a physical change such as removing the solution. The moles of urea will be given by B and C.
A chemical change is called D.
The units on each side have to match.
The mole is per liter.
The rate is determined from the grams of NaOH.
2 base can't be used to titrate the original moles of C2O4. As an acid is needed, it will base.
The molality for the C2O4 is easier to determine.
The Na+ has not reacted. The pressure is still present. The Cl- is from the HCl and can help determine the molarity, but it wouldn't be in solution because it hasn't reacted.
The amount if the solute contains an electrolyte. The solution will conduct electricity and the van's strong electrolytes will exist in solution.
For the operation of a cell to keep the charges, it is necessary to determine the van't in each neutral compartment. If there is no Hoff factor.
Hoff can operate by measuring the osmotic pressure.
Measuring the freezing point of the cell voltage is dependent on the size of the electrode.
The first point of the depression expected for a nonelec order is followed by the radioactive decay process.
The moles of urea kinetics are used to calculate the molarity. The volume of the solution is necessary.
You have 15 minutes to answer the question. You can use the tables in the back of the book.
A sample of a solid weak monoprotic acid, HA, is provided along with solid sodium hydroxide, NaOH, and a phenolphthalein solution.
The dried KHP should be weighed into flasks and dissolved in deionized water.
The acid-base indicator should be added to each sample.
If you rinse a buret with a little NaOH solution, you can fill it with the NaOH solution.
The initial buret reading is a good way to start.
The first pink color will appear after Titrate the NaOH solution into the KHP samples.
Take the last buret reading.
Determine the moles of KHP using the molar mass. This is the same as the moles of NaOH.
The buret readings are different because the NaOH solution volume is added.
The moles of NaOH are divided by the liters of NaOH solution added.
If the items are in order, give yourself 3 points. You only get 2 points for items in the wrong order. You only get 1 point if five to seven items are in the wrong order. You don't get points for less than three items.
You get a point for this graph. The equivalence point is greater than 7.
If you show both steps, you will get 2 points for this graph. One point is given for showing only one step.
The sample can be split into two parts. Add a volume of deionized water equal to the volume of NaOH solution to the untitrated sample.
You get one point for the answer.
There is a chance for 10 points.
Reviewing the experiments should include looking at the synopsis, apparatus, calculations, and comments, as well as the appropriate concept chapters.
Pay particular attention to the experiment you did not perform.
Understand the equipment used in the experiment.
Know the basics of the experiment.
Know which values are measured and which are calculated.
moles are not used to measure the mass of a substance.