AP Chemistry : AP Chemistry

Study concepts, example questions & explanations for AP Chemistry

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Example Questions

Example Question #44 : Laboratory Techniques And Analysis

An experiment calls for you to titrate a  solution of  with a solution of  of unknown concentration. The solution of  is held in an Erlenmeyer flask. What piece of laboratory equipment should you use to administer the  solution?

Possible Answers:

Graduated cylinder

Volumetric pipet

Watch glass and spatula

Buret

Correct answer:

Buret

Explanation:

In a titration, you should use a buret to administer the  solution into the  solution. A buret gives you the most accuracy in running the titration as you can dispense the solution drops at a time. The buret will also allow you to accurately determine the volume of  needed to complete the titration. A watch glass and spatula would be inappropriate for this situation because you are dealing with liquids. Pouring from a graduate cylinder would not be accurate enough and the titration results would be subject to lots of error. A volumetric pipet will not allow you to keep track of the volume needed to complete the titration.

Example Question #45 : Laboratory Techniques And Analysis

An experiment calls for measuring  of a solution in a graduated cylinder. How should the graduated cylinder be read?

Possible Answers:

Hold the graduated cylinder so the meniscus is slightly below eye level, then make sure the bottom of the meniscus is at 

Hold the graduated cylinder so the meniscus is slightly above eye level, then make sure the bottom of the meniscus is at 

Hold the graduated cylinder so the meniscus is at eye level, then make sure the bottom of the meniscus is at 

Crouch down until your head is on the same level as the table top, then look to make sure the bottom of the meniscus is at 

Correct answer:

Hold the graduated cylinder so the meniscus is at eye level, then make sure the bottom of the meniscus is at 

Explanation:

In order for an accurate reading of a graduated cylinder, hold the graduated cylinder at eye level then make sure the bottom of the meniscus is at the desired volume. Having the graduated cylinder slightly below eye level will result in readings that are higher than they are supposed to be. Having the graduated cylinder slightly above eye level will result in readings that are lower than they are supposed to be. Never place your head on the same level as the table to read a graduated cylinder. If the graduated cylinder tips over for any reason, you will splash the solution held within on your face.

Example Question #1 : Laboratory Equipment

While conducting an experiment, you need to measure exactly  of a sulfuric acid solution. Which piece of equipment should you use?

Possible Answers:

Mohr pipette

Graduated cylinder

 beaker

 volumetric pipette

Correct answer:

 volumetric pipette

Explanation:

A volumetric pipette is made to dispense a specific amount of liquid very accurately. The Mohr pipette, beaker, and graduate cylinder will not measure a specific amount of liquid as accurately as the volumetric pipette.

Example Question #47 : Laboratory Techniques And Analysis

While conducting an experiment, you are required to measure out exactly  of potassium hydrogen phthalate. What should you use to measure out the correct amount?

Possible Answers:

Erlenmeyer flask

Triple beam balance

Centigram balance

Analytical balance

Correct answer:

Analytical balance

Explanation:

Potassium hydrogen phthalate is a solid at room temperature, so we can use a balance and a weigh boat or weigh paper. When measuring precise amounts of chemicals, an analytical balance will be able to provide the most accurate reading of mass. 

Example Question #48 : Laboratory Techniques And Analysis

For an experiment, you are required to heat a sample of a solid to very high temperatures. What piece of laboratory equipment should you use to heat the solid?

Possible Answers:

Crucible

Beaker

Erlenmeyer flask

Test tube

Correct answer:

Crucible

Explanation:

When you need to heat anything up to high temperatures, you must use a crucible. Glassware is not able to withstand as much heat as a crucible.

Example Question #1 : Laboratory Equipment

An experiment requires you to mix a solution of  with a solution of  and then observe the reaction. What should the solutions be mixed in?

Possible Answers:

A graduated cylinder

A volumetric pipet

A buret

A beaker

Correct answer:

A beaker

Explanation:

A beaker is the best choice for mixing these two solutions. Graduated cylinders, burets, and pipets are all used to measure specific amounts of solution. Also, stirbars can be easily added to beakers to facilitate the reaction.

Example Question #50 : Laboratory Techniques And Analysis

You are required to find the absorbance of a specific solution. What piece of equipment should you use?

Possible Answers:

Spectrophotometer

Analytical balance

Chromatography paper

Litmus paper

Correct answer:

Spectrophotometer

Explanation:

A spectrophotometer should be used because it is used to measure absorbance at specific wavelengths. An analytical balance is used for measuring mass. Chromatography paper is used to separate different pigments found in a chemical. Litmus paper is used to determine the pH of a substance.

Example Question #11 : Laboratory Equipment And Procedure

Your lab partner is asking you how to properly label a solution of HCl. Which label did you show him?

Possible Answers:

HCl

Concentrated HCl

100mL of hydrochloric acid

1M Hydrochloric Acid

1M of acid

Correct answer:

1M Hydrochloric Acid

Explanation:

When you label chemical solutions, you should technically always use the full chemical name (though this is not always done). Using common abbreviations, like HCl for hydrochloric acid, is generally acceptable. 

The reason why none of the other answers work is because they did not quantify how strong (concentrated) the HCl solution was. A 1 molar HCl solution is handled much differently than a 12 molar one. Even though the answer choice "1M of acid" did quantify the concentration, it did not say which acid was in solution, which would be very unsafe if someone else saw your beaker and needed to know how to dispose of the contents.

Labels should always provide information on the contents of the container, as well as its concentration strength.

Example Question #1 : Chemical Equilibrium

Consider the following gasesous, reversible, exothermic reaction:

What could be done to increase the equilibrium concentration of species C?

Possible Answers:

Increase the reaction temperature

Decrease the amount of species A

Increase the amount of species A

Increase the amount of species E

Correct answer:

Increase the amount of species A

Explanation:

According to Le Chatelier's principle, any changes in concentration or pressure to a system at equilibrium will cause the system to readjust to a new equilbrium. The addition of a reactant will cause the reaction to shift to the right, increasing the equilibirum concentration of the products. Thus, adding additional reactant A would increase the equlibrium concentration of product C.

Removing species A or adding species E will drive the reaction to the left, reducing the amount of species C. Since the reaction is exothermic, heat can be considered a product. Thus, increasing the temperature will also shift the reaction to the left.

Example Question #2 : Equilibrium And Thermodynamics

Consider the following chemical reaction.

This reaction is allowed to equilibrate at some volume and pressure.

Which of the following actions will not shift the equilibrium toward the products?

Possible Answers:

Removing 

Decreasing the pressure

Adding 

Adding an inert gas

Increasing the volume

Correct answer:

Adding an inert gas

Explanation:

Adding an inert gas will not shift the equilibrium toward the products, but neither will it shift the equilibrium toward the reactants. It has no effect because the partial pressure of each species, , , and , will still remain constant. Since the partial pressures are constant, we know from the ideal gas law that the concentration of each species remains constant. For example, for

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