SAT II Chemistry : Compounds and Molecules

Study concepts, example questions & explanations for SAT II Chemistry

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Example Questions

Example Question #1 : Vsepr Theory

Based on VSEPR theory and electron configurations, which of the following molecules is not matched with its correct geometry?

Possible Answers:

 - Linear

 - Linear

 - Trigonal planar

 - Tetrahedral

 - Bent (v-shaped)

Correct answer:

 - Trigonal planar

Explanation:

 has three bonding pairs and one non-bonding pair, which is the geometry for trigonal pyramidal, not trigonal planar.

Example Question #1 : Compounds And Molecules

What is the molecular geometry of ?

Possible Answers:

Octahedral 

Square planar 

Tetrahedral 

Square pyramidal

Trigonal pyramidal 

Correct answer:

Square pyramidal

Explanation:

There are six electron domains in  has five bonding and one nonbonding pairs of electrons. The electron domain geometry of  is octahedral. When a molecule has octahedral electron domain geometry and has five bonding and one nonbonding pairs, the molecular geometry is square pyramidal.

Example Question #1 : Naming Compounds

Which of the following is the correct name of ?

Possible Answers:

Dinitrogen pentoxide 

Dinitrogen tetraoxide

Nitrogen dioxide

Nitrogen monoxide

Dinitrogen monoxide

Correct answer:

Dinitrogen tetraoxide

Explanation:

In order to answer the question, it is important to first determine what kind of bonding is occurring in order to properly name the molecule. When nitrogen and oxygen form an  molecule, electrons are shared between the atoms, so a covalent bond is formed.

Because a covalent bond is formed, we can determine that name of the molecule will be based on number of each atom in the molecule. There are two nitrogen atoms in the resulting molecule, so the prefix in front of the "nitrogen" part of the name will be "di-," meaning two. There are four oxygen atoms in the resulting molecule, so the prefix in front of the "oxygen" part of the name will be "tetra," meaning four.

The molecules names will be arranged alphabetically, and the second atom will have "-ide" as the suffix. Therefore, the correct answer is "dinitrogen tetroxide."

Example Question #1 : Sat Subject Test In Chemistry

What is the formula for the compound formed from calcium and sulfate ions?

Possible Answers:

Correct answer:

Explanation:

In order to answer this question correctly, it is important to have knowledge of the formation of ionic bonds, polyatomic ions, and the periodic table. First, it is important to notice that calcium ions and sulfate ions will form an ionic bond. Knowing this, it can be understood that valance electrons will be exchanged between the ions and therefore, oppositely charged ions that are attracted to each other will be formed.

Calcium is in the second column of the periodic table, so it will provide two ions to the sulfate polyatomic ion. This will form a calcium cation () and a sulfate polyatomic anion ().

One calcium ion provides two electrons, which are both accepted by a sulfate polyatomic ion, so the ratio of calcium ions used to sulfate polyatomic ions used is 1:1. This means that only one of each ion is needed to form the compound, making the formula .

Initially it may be tempting to write the formula as ; however, since both ions have a "2" subscript in this form, it is redundant to the formula in this way. Only one of each ion is needed to form the compound.

Example Question #2 : Sat Subject Test In Chemistry

All of the following are properties of zinc. Which of the following are chemical properties of zinc?

A. Zinc produces hydrogen gas when placed in acid.

B. Zinc melts at .

C. The density of zinc is .

D. Zinc is a grey metal.

E. Zinc corrodes in moist air.

Possible Answers:

 A and E

B and C

B

C

A, C, and E 

Correct answer:

 A and E

Explanation:

Physical properties are aspects of matter that can be observed and measured without changing it. Chemical properties measure the potential for undergoing a chemical change. How zinc reacts to acid and in moist air are both chemical properties because the zinc is undergoing chemical change in each environment. The color, density, and melting point of the zinc can all be observed without changing the nature of the matter, so these are physical properties of zinc.

Example Question #1 : Compounds

Which of the following are strong electrolytes? 

Possible Answers:

Four

All five

Two

Three

One

Correct answer:

Three

Explanation:

Strong electrolytes are substances that exists in solutions as only ions. These substances dissociate 100% in solutions. Strong acids, strong bases, and salts are all examples of strong electrolytes.  is a strong acid.  is a salt.  is a salt.  is a weak acid.   is a weak base. Therefore the answer is three.

Example Question #1 : Ionic Bonds

How many of the following compounds are ionic?

Possible Answers:

All five

Three

Zero

Two

One

Correct answer:

Two

Explanation:

Ionic compounds are chemical compounds made of charged ions held together by forces called ionic bonding. Ionic bonds are formed by transfers of valance electrons, which create charged atoms (ions) which are attracted to each other because they have opposite charges. This is not be confused with covalent bonding, in which atoms form an attraction by sharing electrons.

 contains a positively charged  ion and negatively charged  ion which form an ionic bond.  contains two positively charged  ions and a negatively charged  ion which form an ionic bond. , , and  are all examples of molecules that contain covalent bonds. None of them contains any charged ions. The answer is therefore "two," referring to the  and  molecules.

Example Question #1 : Hydrogen Bonding

Which of the following does not exhibit hydrogen bonding as an intermolecular force?

Possible Answers:

Correct answer:

Explanation:

Hydrogen bonding occurs between hydrogen and a very electronegative atom, which is usually fluorine, oxygen, or nitrogen. Thus, hydrogen bonding does not occur in .

Example Question #1 : Bonding And Forces

In a solution, a weak electrolyte exists predominately as which of the following?

Possible Answers:

Ions

Electrons

Polyatomic ions

Isotopes

Molecules

Correct answer:

Molecules

Explanation:

An electrolyte is a substance that when dissolved in a solution breaks up into ions. More specifically, an electrolyte breaks up into cations (positively charged ions) and anions (negatively charged ions). While strong electrolytes break up 100% into anions and cations, weak electrolytes break apart significantly less. Less than 10% of a weak electrolyte ionizes at all in solution. That means the 90%–99% of the weak electrolyte's molecules do not ionize. This is because the intermolecular forces that form between the solution and the weak electrolyte's molecules are not stronger than the intramolecular forces holding the molecule together. While solutions containing weak electrolytes contain both ions formed from the weak electrolyte ions and molecules of the weak electrolyte, they contain mostly molecules of the weak electrolyte.

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