CHEM EXAM REVIEW

Question 1

Democritus

Answer 1

Matter is made up of tiny indivisible particles called atoms

Question 2

Aristotle

Answer 2

All matter is made up of 4 elements: earth, air, fire, and water

Question 3

Philosophers vs scientists

Answer 3

Philosophers: come up ideas based on intuition and reason

Scientists: come up with ideas through experimentation using tools and technology

Question 4

Dalton’s atomic theory

Answer 4

1. Matter is made up of indivisible atoms called atoms
2. Atoms of the same element elements are identical; atoms of different particles are different
3. Chemical compounds are formed when atoms combine with each other
4. Chemical reactions involve reorganization of atoms, but atoms can not be created or destroyed

Model: “billiard ball”- atom is a featureless sphere

Question 5

Thomson’s experiment

Answer 5

-cathode ray tube
-ray filled with electrons
-reasoned that since atoms are electrically neutral, they must contain a positive charge
Model: plum pudding

Question 6

Rutherford’s famous gold foil experiment

Answer 6

-positively charged alpha particle fire at a thin sheet of gold foil
-nucleus contains protons
-cloud of negatively charged electrons surround nucleus
Model: Beehive

Question 7

chadwick

Answer 7

neutron is a neutral particle in nucleus

Question 8

Bohr’s Experiment

Answer 8

-continuous spectrum: white light passing through prism
-emission spectrum: passing light from a hydrogen gas cathode ray tube through a prism

Question 9

Bohr

Answer 9

-proposed electrons could move only in specific orbits around the nucleus
Bohr: planetary model

Question 10

periodic law

Answer 10

when atoms are arranged in order of increasing atomic number, their properties show a recurrence and gradual change

Question 11

atomic radius

Answer 11

measurement of the size of an atom

Question 12

effective nuclear charge

Answer 12

-net force experienced by an electron in an atom due to the positively charged nucleus
Greater the effective nuclear charge, the smaller the atomic radius
-Radius decreases going across and increases going down the periodic table
In my own words: the more the electron orbits, the stronger the nuclear charge, pulling them close to the nucleus, making the radius small
-Cations always smaller than original atoms because they lose electrons
-Anions: always larger than their original atoms cause they gain electrons

Question 13

Ionization energy

Answer 13

-quantity of energy required to remove an electron from an atom or ion
-Increases moving across and decreases moving down
In my own words: the further an electron is from a nucleus the easier it is to remove it because the inner electrons shield them from the positive charged nucleus

Question 14

electron affinity

Answer 14

-Energy change that occurs when an electron is added to a neutral atom
-Increases moving across and decreases moving down
-Larger atoms have a weak attractive force from the nucleus and a strong repulsive for from the electrons
-In my own words: larger atoms have more electrons causing they to have a stronger repulsive force from the positive nucleus because the nucleus has a weaker attraction to more electrons

Question 15

properties of ionic compounds

Answer 15

-form crystal lattice structure
-high melting and boiling points
-hard
-brittle
-conduct electricity
-electrolytes

Question 16

non polar covalent vs polar covalent

Answer 16

-Nonpolar covalent bond: electrons are shared equally between atoms
-Polar covalent: electrons are not shared equally because one atom attracts them more strongly than the other atom

Question 17

dipoles

Answer 17

-Separation of positive and negative charges in a region of space
-A polar bond will have a slightly positive end and a slightly negative end
-Represented using an arrow, arrow points toward more negative end

Question 18

electronegativity

Answer 18

-ability of an atom in a molecule to attract shared electrons to itself
-increases going across decreases going down periodic table
-calculating the difference gives us information about the bond they will form
-draw arrow for polar bonds

Question 19

intramolecular

Answer 19

chemical bond within a molecule

Question 20

intermolecular

Answer 20

force occurs between molecules

Question 21

london dispersion force

Answer 21

result from a random momentary non symmetrical electron distribution
-electrons from one molecule being attracted to the positive nucleus of an adjacent molecule
-all molecules experience it
-weakest
-strength increases with size, surface of contact or proximity
-low melting and boiling points

Question 22

dipole-dipole

Answer 22

-electrostatic attraction caused when dipoles of polar molecules position their positive ends near each other
-only experienced by polar molecules
-strength increases with polarity, decreased distance between molecules
-intermediate melting and boiling points

Question 23

hydrogen bonds

Answer 23

-strong dipole-dipole attraction
-occurs when a hydrogen atom bonded to a small highly electronegative atom (oxygen, nitrogen, or fluorine) is attracted to a partially negative atom on a nearby molecule
-strongest
-high melting and boiling points
-solid at room temp
-high surface tension

Question 24

complete combustion vs incomplete combustion

Answer 24

Complete combustion
-oxygen supply is plentiful
-products are CO2 and H20
-very efficient because max amount of energy is produced

Incomplete combustion
-oxygen supply is limited
-products are CO2, H20, C, C0
-less efficient because less energy is produced

Question 25

hydrocarbons

Answer 25

organic compounds made up of entirely of carbon and hydrogen atoms
Properties (ex: methane CH4, Propane C3H8)

Non polar
Insoluble in water
Can exist as gases, liquids, or solids at room temperature

Question 26

Law of definite proportions:

Answer 26

elements in a compound are always present in the same proportion by mass

Question 27

stoichiometry

Answer 27

study of mass and mole relationship between reacts and products in a chemical reaction

Question 28

characteristic of solutions

Answer 28

Homogeneous: uniform composition throughout
Stable: solute particles do not settle over time
Can exist in various phases solid, liquid, or gas

Question 29

disassociation

Answer 29

ionic compounds separate into individual ions in water

Ex. Na Cl -> Na+ (aq) + Cl- (aq)

Question 30

hydration

Answer 30

water molecules surround and stabilize ions

Question 31

miscibility and factors affecting it

Answer 31

ability of 2 liquids to mix and form a homogeneous solution

Factors affecting miscibility:
-Like dissolves like
-Intermolecular forces: hydrogen, dipole-dipole

Question 32

surfactants

Answer 32

reduce surface tension between 2 substances, allowing them to mix

-Hydrophilic head: polar part that interacts with water
-Hydrophobic tail: nonpolar part interacts with oils and grease

Question 33

concentration

Answer 33

amount of solute dissolved in a given quantity of solvent or solution

Question 34

stock solution

Answer 34

highly concentrated solution used as a starting point to prepare more dilute solutions for practical applications

Question 35

standard solution

Answer 35

solution prepared with precisely known concentration, often used for experiments and calibrations

Question 36

strong acid vs weak acid

Answer 36

Strong acid: ionizes completely in water
Weak acid: substance only partially ionizes in water

Question 37

titration, equivalence point, endpoint

Answer 37

-Titration: procedure use to determine the concentration of one solution
-Equivalence point: point in titration when neutralization is complete
-Endpoint: point in titration when indicator changes color (titration is complete)

Question 38

Standard temperature and pressure

Answer 38

O degrees , 101.325 kPa

Question 39

standard ambient temperature and pressure

Answer 39

25 degrees, 100 kPa

Question 40

ideal gas law

Answer 40

hypothetical gas composed of no particles, have no size, travel in straight lines, have no attraction to each other. No such thing. We assume gases are ideal in order to simplify our equations to predict the behavior of real gases in most situations

Question 41

Why do solids have a definite shape and volume?

Answer 41

Solids have a definite shape and volume because their particles are tightly packed in a fixed, orderly arrangement. The intermolecular forces in solids are strong, restricting the motion of particles to only vibrations around fixed positions. This rigidity prevents changes in shape or volume under normal conditions.

Question 42

Why are gases relatively easy to compress while solids are virtually incompressible?

Answer 42

Gases are easy to compress because the particles in a gas are far apart and have large spaces between them, allowing them to be pushed closer together. In contrast, solids are virtually incompressible because their particles are already packed closely together in a fixed structure, leaving little to no space for compression.

Question 43

Why do gases and liquids flow, while solids do not?

Answer 43

Gases and liquids flow because their particles can move past each other. In gases, particles are in constant, random motion with negligible attractive forces. In liquids, the particles are close but not fixed, allowing movement. Solids do not flow because their particles are locked in a rigid lattice, preventing relative movement.

Question 44

Define STP and SATP

Answer 44

STP (Standard Temperature and Pressure): Defined as a temperature of 0°C (273.15 K) and a pressure of 1 atm (101.3 kPa).

SATP (Standard Ambient Temperature and Pressure): Defined as a temperature of 25°C (298.15 K) and a pressure of 1 bar (100 kPa).

Question 45

(b) Explain why scientists have defined two sets of standard conditions.

(c) Which standard is most frequently used, and why?
SATP is more frequently used because it represents conditions closer to real-world temperatures and pressures encountered in laboratories and daily life, making it more practical for most applications.

Answer 45

(b) Explain why scientists have defined two sets of standard conditions.
STP is used for calculations requiring precise and controlled baseline conditions, often in scientific research. SATP reflects conditions closer to everyday ambient environments, making it more practical for general chemical and industrial applications.

(c) Which standard is most frequently used, and why?
SATP is more frequently used because it represents conditions closer to real-world temperatures and pressures encountered in laboratories and daily life, making it more practical for most applications.

Question 46

What happens to a sample of matter cooled to absolute zero?

Answer 46

At absolute zero (0 K or -273.15°C), the motion of particles theoretically ceases entirely. In this state, a substance would have no thermal energy, and all particles would occupy their lowest energy state. In reality, absolute zero is unattainable, but approaching it leads to phenomena like superconductivity and superfluidity.