Chemistry TCB Exam Flashcards

chemistry =
study of substances and the changes they undergo
Describe the Atlantic/Pacific rule.

decimal Absent: start on the Atlantic side of the number, count the first non-zero number and all that follow

decimal Present: start on Pacific side of the number, count the first non-zero number and count all that follow

How many sig figs do I use when measuring things in lab situations?  (ex. graduated cylinder or ruler)
go to the nearest line given, then estimate one decimal past that (if a graduated cylinder shows lines every 1mL, your answer should be to the nearest 1/10mL  ex. 10.5mL)
accuracy
how close a measurement is to the real answer
precision
how close a measurement is to other measurements

How many sig figs in:

7.2340

0.03460

1,340.01

5

4

6

How do we measure density?
mass/volume

Put the following in scientific notation:

5,245,252

0.00346

5.25×10^6

3.46×10^-3

If I shoot my bow, and I consistently hit low and to the left, are my shots precise or accurate or both?
precise (the shots are consistent, but not accurate, that is, they’re not close to the bullseye)

Convert the following:

1,288 inches = ____? meters

2.54cm / inch

3,271.52cm

or

3,270cm (3 sig figs)

independent variable
the thing I change/control
dependent variable(s)
the thing(s) you measure
law of conservation of energy
energy is neither created or destroyed
law of conservation of mass
mass is neither created or destroyed
law of conservation of matter
matter is neither created or destroyed

Which can NOT be broken down any further?

sodium, disulfate, diatomic oxygen, hydroxide

sodium, because its an element.; The rest are either molecules or compounds
Is a phase change a chemical change or a physical change?
Physical change because its only changing forms, not creating something new
chemical change
when a chemical reaction takes place and new products are formed
Which state of matter is typically the LEAST dense?
Gas
What is an alpha particle?
a helium nucleus (2 protons, 2 neutrons)
How do you balance nuclear equations?
balance the top number (mass number) and balance the bottom number (atomic number)
If the result of a nuclear equation is a particle with a mass number of 4 and atomic number of 2, what type of nuclear reaction happened?
alpha decay, because an alpha particle has an atomic # of 2 and mass # of 4.
If the result of a nuclear equation is a particle with a mass number of 0 and atomic number of -1, what type of nuclear reaction happened?
beta decay, because the result of beta decay is the decay of a neutron into a proton and the release of an electron

Match the scientist:

Bohr;;;;;;;;;;;;;;;;;; gold foil experiment

JJ Thomson;;;;;;; planet model of atom

Rutherford;;;;;;;; ; ; ; ; ; ;; plum pudding

Bohr:; planetary model

Thomson:; plum pudding

Rutherford:; gold foil

What did the gold foil experiment done by Rutherford prove?
atoms have very tiny, but very dense nuclei
If I started with 48g of Carbon-12, and 1yr later I have 38g, what term describes what has happened?
radioactive decay
If the half-life of carbon-12 is 5.73yrs, and I started with 100g, how much is left after 11.46yrs?

25 grams

because 11.46yrs is 2 half-lives

100g–>50g–>25g

How many half-lives does it take to have 1/16 of the original sample left?

4 half-lives

1–>1/2–>1/4–>1/8–>1/16

If the mass number of element X is 48, and it has 22 protons, how many neutrons does it have?

26 neutrons

48 – 22 = 26

If the atomic number of element X is 43 and it contains 41 electrons, what is the ion charge?

+2

 

What does the neutron do for an atom?

 

Three important things:

1.  it supplies the force that holds the nucleus together

2.  it makes the atom more stable

3.  it is the “glue” of the nucleus

What is the atomic mass of element X:

isotope 1: 18.32amu, abundance 21.30%

isotope 2: 19.27amu, abundance 70.20%

isotope 3: 20.11amu, abundance 8.50%

19.14amu

18.32 x .2130 = 3.90

19.27 x .7020 = 13.53

20.11 x .0850 = 1.71

electrons have several energy levels, which contain _____, which contain _______ that each hold a pair of electrons.

sublevels

orbitals

s, p, d and f describe what?
electron sublevels (and areas on the periodic table that contain those sublevels)
What is the shape of the s-sublevel?
sphere
What is the shape of the p-sublevel?
dumb bell shape

How many valence electrons do the following have?

Na, C, Ne

Na = 1

C = 6

Ne = 8

What element has the same electron configuration as Al+3?

Neon

because aluminum lost 3 electrons, giving it the same configuration as the element with 3 less electrons

If we vaporize an element in a flame, what type of light is given off?
only specific wavelengths of light, which are based on the energy given off by the electrons as they fall back to their “ground state”
What color of light has the highest energy? lowest?

highest: violet

lowest: red

What is the electron configuration for Fe (iron)?
1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d8
Why are valence electrons important?
they are the electrons involved in reactions and bonding
What halogen has the highest ionization energy? Why?
Fluorine because its outermost electron is closest to the nucleus
ionization energy
energy needed to “pluck” an electron from an atom;  increases as you go right and up on the periodic table
Ionization energy is similar to what other trend on the periodic table?
electron affinity
atomic radius
measure of the size of an atom; it increases down a group, but decreases across a period
Why does atomic radius decrease across a period?
because as electrons and protons are added, the attraction between the nucleus and electrons increases, making the atom more “condensed”
When an atom gains electrons, it

gets larger

becomes an ion

has a negative charge

Metals typically form ___ ions and are found on the ___ of the periodic table.  Non-metals typically form ___ ions and are found on the ___ of the periodic table.

positive, left

negative, right

What is the difference between ionization energy and electron affinity?

ionization energy= energy required to “pluck” an electron from the atom

electron affinity= energy given off when an electron is gained

Which “block” contains the alkali metals and alkaline earth metals?
s-block
Which “block” contains the non-metals?
p-block
Which “block” contains the transition metals?
d-block
What makes transition metals unique?

They are:

good conductors of heat/electricity

shiny, malleable, ductile

What makes alkali metals and alkaline earth metals unique?
they are highly reactive, soft metals
What makes the halogens unique?
they are highly reactive non-metals
Air is a mixture of gases including oxygen, nitrogen, helium, hydrogen and traces of other gases.  Which gas makes up most (70+%) of earth’s air?
nitrogen
Which “block” on the periodic table is the only one that contains both metals and non-metals?
p-block

What is the formula for the following:

sulfate

sulfide

ammonia

ammonium

SO4-2

S-2

NH3

NH4+1

When atoms lose or gain electrons, they are trying to form stable electron configurations similar to which family?
noble gases

Name the compound:

NaNO3

SBr3

CaF2

KCl * 5H2O

sodium nitrate

sulfur tribromide

calcium fluoride

potassium chloride pentahydrate

When is the prefix “mono” used in naming compounds?
only on the second word of a covalent compound, never on the first.

What does the Roman numeral next to a transition metal tell you?

ex. copper (II) sulfate

it tells you the ion charge (positive) on the transition metal

What does an acid have in its formula?

What does a base have in its formula?

H+ ion

OH- ion

Which is the stronger covalent bond, a single bond or double bond or triple bond?
triple is strongest, then double, then single
Which covalent bonds are the longest, single, double or triple bonds?
single bonds are longest, then double, then triple
How many single covalent bonds can one carbon atom have?
4
alkane

single chain hydrocarbon with the formula

CnH*2n +2

ex. C8H18

What does “Max eats peanut butter” refer to?

naming alkanes and alcohols

Max = methane/methanol

eats = ethane/ethanol

peanut = propane/propanol

butter = butane/butanol

allotrope
a pure substance with different structural forms
What are the three most common allotropes of carbon?

graphite

diamond

buckminster fullerine (buckyball)

alcohol

a hydrocarbon in which a hydroxide (OH) has replaced CH3 on one side of an alkane

ex. ethane = CH3CH2CH3

ethanol = CH3CH2OH

What are alcohols most used for?
they are burned for fuel
alloy
a mixture containing metals produced by melting them together

Which of the following is NOT an alloy?

steel

bronze

silver

brass

silver, it is an element
molarity

moles per liter

mol/L

molality

moles per kilogram

mol/kg

What formula do we use to calculate Molarity?
Molarity = # mols / molar mass
In words, what is molarity?
concentration of a substance in a liquid (usually water)
How do we figure out the number of mols of a substance?
# mols = grams of substance / molar mass
How do we figure out molar mass?

1. Look up each element’s mass

2. Multiply by the # of atoms of that element

3.  Add all the numbers together

What is Avogadro’s Number?

6.02 X 10^23

or 1 mole

How do we calculate the number of particles of a substance?
# particles = (# mols ) X (6.02 X 10^23)

What type of reaction is shown below?

 

2HgO —>  2Hg + O2

decomposition reaction

What type of reaction is shown below?

 

2Mg + O2 —>  2MgO

combination reaction OR

synthesis reaction

What type of reaction is shown below:

 

2K + 2H2O —>  2KOH + H2

single replacement reaction

What type of reaction is shown below:

 

Br2 + 2NaI —>  2NaBr + I2

single replacement reaction
What must be true for a metal to replace another metal (or hydrogen) in a single replacement reaction?
it must be more reactive (from the activity series chart) than the one it replaces

What type of reaction is shown below:

 

Na2S + Cd(NO3)2 —>  CdS + 2NaNO3

double replacement reaction

Balance this reaction:

 

NaCN + H2SO4 —>  HCN + Na2SO4

2NaCN + H2SO4 —>  2HCN + Na2SO4

Balance this equation, give the type of reaction and name the compounds:

 

Ca(OH)2 + HCl —>  CaCl2 + H2O

Ca(OH)2 + 2HCl —>  CaCl2 + 2H2O

double replacement reaction

calcium hydroxide + hydrogen chloride (hydrochloric acid)  —> calcium chloride + dihydrogen monoxide (water)

What type of reaction is shown below,  and name the compounds:

 

2C8H18 + 25O2 —>  16CO2 + 18H2O

combustion (burning) reaction

 

octane (gasoline) + diatomic oxygen (oxygen gas) —>  carbon dioxide + dihydrogen monoxide (water)

How many total electrons are involved in a double covalent bond?
4
polarity
describes if a molecule has a positive side and a negative side; like a magnet
How do we determine whether a molecule is polar or non-polar?

check the electronegativity chart: 

a difference greater than 0.4 means polar…if the molecule is diatomic, it must be non-polar

electronegativity
a number given to elements to describe “how negative” or “how positive” they are

Determine if the following is polar or non-polar:

Na2S

O2

TeCl2

Electronegativities: Na=0.9  S=2.5  O=3.5  Te=2.1  Cl=3.0

Na2S  —>  polar (EN:  2.5-0.9=1.6)

O2 —->  non-polar (diatomic)

TeCl2 —-> polar (EN: 3.0-2.1=0.9)

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