AP Chemistry : Hypotheses and Procedures

Study concepts, example questions & explanations for AP Chemistry

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Example Questions

Example Question #1 : Hypotheses And Procedures

You have a stock solution of 12M HCl, but want to dilute it to 1M HCl. What is the safest way you could go about doing this?

Possible Answers:

Measure out the water first, then rapidly add the correct amount of 12M HCl

Measure out the water first, then slowly add the correct amount of 12M HCl

Measure out the 12M HCl first, then rapidly add the correct amount of water

Add the correct amount of water and 12M HCl to a common beaker at the same time

Measure out the 12M HCl first, then slowly add the correct amount of water

Correct answer:

Measure out the water first, then slowly add the correct amount of 12M HCl

Explanation:

Always add acid to water. You should mix solutions slowly because you run the risk of solutions spilling, which may ruin your reaction entirely. Rapid mixing can also lead to inadvertently speeding up reactions and releasing energy or heat in a dangerous manner. During dilution of acids with, water heat is released; if a small amount of water is added to a concentrated acid it has the possibility of bubbling over the counter and onto you. 

Example Question #42 : Laboratory Techniques And Analysis

Which procedure separates two substances using their different boiling points?

Possible Answers:

Dehydration

Hydration

Fermentation

Distillation

Filtration

Correct answer:

Distillation

Explanation:

During the distillation process, the combined substances are heated until the first one boils. The substance that boils and becomes a gas is then separated from the still liquid or solid substance via condensation into a separate container. Filtration involves separating substances in solid and liquid phases through a filter paper, and is often facilitated by a vacuum. Dehydration and hydration are types of reactions where water is a product, and a reactant, respectively. Fermentation is a biochemical process that occurs under anaerobic conditions. Some organisms produce lactic acid as a byproduct of fermentation, (humans), others produce ethanol (yeast). 

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