Chemistry CLEP

Hydrogen bonds

weak bonds; attractive forces in which a hydrogen covalently bonded to a very electronegative atom is also weakly bonded to an unshared electron pair of another electronegative atom

Ionic bonds

the electrostatic forces that hold ions together in ionic compounds; transfer of electrons

Polar covalent bonds

unequal sharing of electrons

London dispersion forces

the intermolecular attraction resulting from the uneven distribution of electrons and the creation of temporary dipoles

ion-dipole

ion and polar molecule

The attractions between atoms within a molecule of NH3 are best characterized as

polar covalent bonds

Trigonal planar molecule

- 3 bonds

- 120 degree angles

- 2D e.g: BF3

Trigonal pyramidal

3 bonds, 1 lone pair, 107.5 degree angle

square pyramidal

5 bonds, 1 lone pair, 90 degree angle

bent

104.5

tetrahedral

4 bonds, 0 lone pairs, 109.5

The geometry of the SO3 molecule is best described as

trigonal planar

Pi bonds

forms when parallel orbitals overlap and share electrons; two bonds

Sigma bonds

single covalent bonds

pi bonding occurs in each of the following species EXCEPT

- CO2

- C2H4

- CN

- C6H6

- CH4

CH4

Which of the following is a correct interpretation of the results of Rutherford's experiments in which gold atoms were bombarded with alpha particles?

- Atoms have equal numbers of positive and negative charges

- Electrons in atoms are arranged in shells

- Neutrons are at the center of an atom

- Neutrons and protons in atoms have nearly equal mass

- The positive charge of an atom is concentrated in a small region

The positive charge of an atom is concentrated in a small region

What is the correct ground state electron configuration for Fe?

1s^2

2s^

2p^6

3s^2

3p^6

4s^2

3d^6

Based on their positions in the periodic table, list the following atoms in order of increasing radius: Mg, Ca, Rb, Cs

Mg < Ca < Rb < Cs

atomic radius \_______ across a period and \________ down a group

decreases ; increases

Methionine, CH3SCH2CH2CH (NH2) CO2H, is an amino acid found in proteins. What is the hybridization type of the nitrogen?

sp3

hybridization

the mixing of several atomic orbitals to form the same total number of equivalent hybrid orbitals

Predict what mode(s) of spontaneous radioactive decay the unstable isotope 6/2He might proceed

beta decay

alpha decay

4/2 He

positron emission

0/+1 e

electron capture

the process in which an inner orbital electron is captured by the nucleus of the atom that contains the electron

beta decay

radioactive decay in which an electron is emitted.

gamma decay

the release of gamma rays from a nucleus

Which of the following represents the number of moles of an ideal gas in a 2.0L container at 3.0 atm and 450 K?

(3.0) (2.0)/ (0.0821) (450) mol

Each of three flexible vessels contains a gas at the same temperature and pressure. The first contains 2.0g of H2 (g), the second contains 32.0 g of O2, 44.0g of CO2 (g), and the third contains 44.0g of CO2 (g). Which of the following statements about gases in FALSE?

- The densities of the gases increase in order H2 < O2 < CO2

- The number of molecules in each of the three vessels is the same

- The volume of each three vessels is the same

- The average kinetic energy of the molecules in each of the vessels is the same

- The average speed of the molecules in each of the vessels is the same

FALSE: The average speed of the molecules in each of the vessels is the same

In the formation of 1.0 mole of the following crystalline solids from the gaseous ions, the most energy is released by

- NaF

- MgF2

- BrBr2

- AlF3

- AlBr3

AlF3

The critical temperature of a substance is the

- temperature at which the vapor pressure of the liquid is equal to the external pressure

- temperature at which the vapor pressure of the liquid is equal to 760 mm Hg

- temperature at which the solid, liquid, and vapor phases are all in equilibrium

- temperature above which a substance cannot be liquefied at any applied pressure

lowest temperature above which a substance cannot be liquefied at any applied pressure

Question 13 of CLEP review is where you left off

Recrystallization refers to technique for

purification of solids

Distillation is the

separation of liquids based on boiling points and varies depending on temperature and external pressure

Extraction is

a technique used to purify liquid-liquid or liquid-solid systems

Chromatography is

the separation of compounds based on polarity

Recrystallization is the common technique for

the purification of solids

Recrystallization principle

solid and solid impurities can be separated from each other by selective dissolution

How does recrystallization work?

You dissolve the solid in a liquid (solvent) so that it is insoluble at low temperature but soluble at high temperature.

The impurities will remain undissolved so they can be filtered off.

Upon cooling, recrystallization will occur.

This may be an iterative process

iterative

A process in which a set of steps or instructions is repeatedly executed until a predefined or natural end point is reached

Distillation is

the separation of liquids based on boiling points

Vapor pressure

pressure that a gas exerts on a liquid at equilibrium

Boiling occurs when

the atmospheric (outer) pressure is equal to the vapor pressure (VP)

Dependence of vapor pressure on temperature and external pressure

- normal bp\= T at which equilibrium is reached when the external pressure is 1 atm

- At reduced pressure (vacuum), the temperature required for boiling is lower