AP Chemistry : Molecular Structure of Acids and Bases

Study concepts, example questions & explanations for AP Chemistry

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Example Questions

Example Question #141 : Reactions And Equilibrium

Put the following acids in order of their INCREASING acid strength:  HI, HCl, HBr, HF.

Possible Answers:

HI, HCl, HBr, HF

HCl, HBr, HI, HF

HI, HBr, HCl, HF

HF, HBR, HI, HCl

HF, HCl, HBr, HI

Correct answer:

HF, HCl, HBr, HI

Explanation:

Larger halogen size leads to greater acidity because of weaker H-X interactions.

Example Question #1 : Molecular Structure Of Acids And Bases

Put the following acids in order of their INCREASING acid strength:  HCl, HS, HBr, H2Se.

Possible Answers:

H2Se, HBr, HS, HCl

HCl, HS, HBr, H2Se

H2S, HCl, HBr, H2Se

HBr, H2Se, HCl, H2S

H2S, H2Se, HCl, HBr

Correct answer:

H2S, H2Se, HCl, HBr

Explanation:

Acid strength increases from left to right across a period and increases going down a group.

Example Question #2 : Molecular Structure Of Acids And Bases

Put the following acids in order of their DECREASING acid strength:  HOCl, HOBr, HOI, H2O.

Possible Answers:

H2O, HOI, HOBr, HOCl

H2O, HOCl, HOBr, HOI

HOI, HOBr, HOCl, H2O

HOCl, HOBr, HOI, H2O

HOCl, H2O, HOBr, HOI

Correct answer:

HOCl, HOBr, HOI, H2O

Explanation:

Acid strength of an oxy acid increases with increasing electronegativity on the halogen.

Example Question #91 : Reaction Types

Put the following acids in order of their DECREASING acid strength:  HOCl, HO2Cl, HO3Cl, HO4Cl.

Possible Answers:

HOCl, HO4Cl, HO2Cl, HO3Cl

HOCL, HO2Cl, HO3Cl, HO4Cl

HO4Cl, HO3Cl, HO2Cl, HOCl

HO4Cl, HOCl, HO2Cl, HO3Cl

HO2Cl, HOCl, HO3Cl, HO4Cl

Correct answer:

HOCL, HO2Cl, HO3Cl, HO4Cl

Explanation:

For an oxyacid, the acid strength increases as the number of oxygens increase.

Example Question #92 : Reaction Types

Put the following in order of INCREASING acid strength:  H2Se, KH, AsH3, HBr.

Possible Answers:

HBr, H2Se, AsH3, KH

KH, AsH3, H2Se, HBr

KH, H2Se, AsH3, HBr

AsH3, H2Se, HBr, KH

AsH3, H2Se, KH, HBr

Correct answer:

KH, AsH3, H2Se, HBr

Explanation:

Acid strength increases going across a period.

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