MCAT Chapters 1 & 2

8/14/2019 MCAT Chapters 1 & 2

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MCATCHEMISTRY

Review 1


2/19

DIMENSIONAL ANALYSIS

We use dimensional analysis as a tool to interconvert between units.

-Design the problems to ______________ with your known, and to _____________ with the unit of

your unknown.

EXAMPLE 1: A sample of gaseous N2contains 0.10 moles and occupies a volume of 7.0 m3. Find its density

in g/cm3.

a. 0.40 g/cm3.b. 4.0 x 10-3g/cm3.c. 4.0 x 10-5g/cm3.d. 4.0 x 10-7g/cm3.

EXAMPLE 2:If a person is taking a prescription of Betaxol after surgery and the recommended dosage is 50.0

mg/kg of body mass. Calculate the recommended dosage for a person who weighs 100 lbs.


3/19

MASS CONVERSIONS

The_______________is the chemical unit for the amount of a substance.

One mole (1 mol) contains 6.022 x 1023

entities, which is known as __________________________________.

Entities means______________________ , ______________________ or ______________________ We use______________________when dealing with a single, individual element. We use_________________or _________________when dealing with more than one element or a

compound.

6.022 x 1023

atoms of Fe is equal to 1 mole of Fe and has a mass of 55.85 amu

EXAMPLE: Determine the number of oxygen atoms in 16.0 grams of ozone, O3?

Use Avogadros Number

6.022 x 1023

Use Atomic Mass

Atoms Moles Grams


4/19

6.022 x 1023

molecules of HClis equal to 1 mole of HCl and has a mass of 36.46 amu

EXAMPLE 1: Determine the grams of water found in 3.01 x 1024

oxygen.

EXAMPLE 2: What is the number of ammonia, NH3, molecules found in 170.0 g NH3?

Molecules Moles Grams

Use Avogadros Number

6.022 x 1023

Use Molecular Mass


5/19

MASS PERCENT

Mass or weight percent is the percentage of a given element in a compound.

EXAMPLE 1: What is the mass percent of oxygen in calcium carbonate, CaCO3?

a. 40%b. 25%c. 16%d. 48%

EXAMPLE 2: What is the mass percent of a 1.0 m NaOH solution?

a. 4.0%b. 3.0%c. 3.8%d. 5.0%

EXAMPLE 3: What is the mass percent of a 2.8 M KOH solution with a density of 1.50 g/cm3?

a. 7.2%b. 5.8%c. 6.3%d. 9.0%

Mass Percent (%)=Mass Component

Total Mass of Compound 100


6/19

STOICHIOMETRIC REACTIONS

In the above equation the numbers that are in bold are called_______________________.

They tell us the number of______________of each compound that reacts.This numerical relationship between compounds in a balanced equation is called__________________________.

STOICHIOMETRIC CHART

Before we get into solving stoichiometric reactions lets work out a plan of attack.

Entities means______________________ , ______________________ or ______________________.

Use this chart when given a chemical equation with the____________quantity of a compound or element and

asked to find the____________quantity of another compound or element.

2 H2(g) + 1O2(g) 2H2O (g)

Entities of Given

Grams of Given

Entities of Unknown

Grams of Unknown

Moles of Given Moles of Unknown


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EXAMPLE 1:How many grams of calcium chloride are needed to prepare 72 g of silver chloride according to

the following equation?

CaCl2(aq) + 2 AgNO3(aq) Ca(NO3)2(aq) + 2 AgCl (s)

EXAMPLE 2: What is the percent yield for a reaction in which 27 g of Cu is produced by reacting 32.5 g of Zn

in excess CuSO4solution?

Zn (s) + CuSO4(aq) Cu (s) + ZnSO4(aq)

a. 84%b. 75%c. 90%d. 50%

EXAMPLE 3: A sodium azide air bag inflates to a volume of 45 Liters at STP. According to the information

contained in the passage, what is the mass of NaN3 (Mol. Wt. = 65) that is required to inflate the bag?

2 NaN3 2 Na + 3 N2

a. 76 gramsb. 81 gramsc. 87 gramsd. 130 grams


8/19

MOLARITY

Molarity (M)can serve as the connection between the interconversion of____________ to____________and

vice versa.

For example, a 5.8 M NaClsolution really means_______________________per_____________________.

A typical mixture consists of a smaller amount of one substance, the ________________, dissolved in a larger

amount of another substance, the __________________. Together they form a __________________.

EXAMPLE 1:Stock hydrochloric acid solution is 36.0% by volume HCl. If you assume that the density of the solution is 2.50

g/cm3.What is the molarity of the solution?

Molarity =MolesSolute)(

LitersSolution)(


9/19

SOLUBILITY

The ___________________________ of a compound represents the maximum amount of solute that dissolves in a solvent

SOLUBILITY RULES

SOLUBLE IONIC COMPOUNDS INSOLUBLE IONIC COMPOUNDS

1. Group 1A ions (Li+, Na+, K+, etc.)and ammoniumion (NH4+)are soluble.

1. (Hydroxides) OH-and (Sulfides) S2-, are insolubleexceptwhen with Group 1A ions (Li+, Na+, K+, etc.),

ammonium ion (NH4+) and Ca2+, Sr2+, Ba2+.

2. (Nitrates) NO3-, (acetates) CH3COO-or C2H3O2-,and most perchlorates (ClO4-)are soluble.

2. (Carbonates) CO32-and (Phosphates) PO43-are

insoluble exceptwhen with Group 1A ions

(Li+, Na+, K+, etc.), ammonium ion (NH4+).

3. Cl-, Br-, and I-are soluble, exceptwhen pairedwith Ag+, Pb2+.

4. (Sulfates) SO42-are soluble, exceptthose of Ca2+,Sr2+, Ba2+, Ag+, Hg2+and Pb2+.

When we classify a compound as solubleit means that the compound is_______________________, it is also known as

a(n)_______________________because it conducts electricity.

NaNO3(s) Na+(aq) + NO3 (aq)

When we classify a compound as insolubleit means that the compound is a_______________________, it is also known

as a(n)_______________________because it doesnt conduct electricity.

CH3OH (l) CH3OH (aq)

BaSO4(s) BaSO4(aq)

H2O

H2O

H2O


10/19

OXIDATION-REDUCTION REACTIONS

Chemists use some important terminology to describe the movement of electrons.

In______________reactions we have the movement of electrons from one reactant to another.

Rules for Assigning an Oxidation Number (O.N.)

A. General Rules1. For an atom in its elemental form (Na, O2, S8, etc.): Oxidation #=02. For an ion the O.N. equals the charge: Na+, Ca2+, NO3

B. Specific Rules1. Group 1A: O.N. = +12. Group 2A: O.N. = +23. For hydrogen: O.N. = +1 with nonmetals

O.N. = -1 with metals and boron

4. For Fluorine: O.N. = -1

5. For oxygen: O.N. = -1 in peroxides (X2O2 , X = Group 1(A) element)

O.N. =1

2in superoxides (XO2, X = Group 1(A) element)

O.N. = - 2 in all other compounds

6. Group 7A O.N. = -1 (except when connected to O)

L

E

O

G

E

R

Agent Agent


11/19

EXAMPLE:Give the oxidation number of the underlined atom in the following molecules and ions:

a) PO43- c) H3AsO4

b) V2O52- d) NaO2

EXAMPLE 2:Use the following choices to answer the following questions:

a. Metathesis b. Acid-Base c. Hydrogen Displacement d. Combustion e. Metal Displacement

a) Ba(NO3)2 (aq) + Na2SO4 BaSO4(s) + 2 NaNO3 (aq)

b) Mg (s) + 2 HCl (aq) MgCl2 (aq) + H2(g)

c) Ca (s) + 2 LiNO3(aq) Ca(NO3)2(aq) + 2 Li (s)

d) C3H8 (g) + 5 O2(g) 3 CO2 (g) + 4 H2O (g)

e) NaOH (aq) + HBr (aq) H2O (l) + NaBr (aq)


12/19

ELECTRON ORBITAL THEORY

The main atomic sub-levels are the s, p, dand f. Each atomic sub-level has a set number of atomic or electron orbitals.

Each electron orbital can hold up________electrons.

The ssub-level contains one electron orbital _______

Thepsub-level contains three electron orbitals

_______ _______ _______

The dsub-level contains five electron orbitals

_______ _______ _______ _______ _______

The fsub-level contains seven electron orbitals

_______ _______ _______ _______ _______ _______ _______


13/19

ELECTRONIC STRUCTURE

In this chapter we will focus on how an elements________________________________________ - the distribution of

electrons within the orbitals of its atomsrelates to its chemical and physical properties.

History Lesson:In 1870, Dmitri Mendeleev arranged 65 elements into a ___________________________________ .

He summarized their behavior in the _______________________________. When arranged by atomic mass, the elements exhibit a periodic recurrence of similar properties.

The Electron Configuration

According to the______________Principleyou first have to totally fill in the lowest energy level before moving to the next.

According to the______________Principleno two electrons can have the same four quantum numbers.

Hunds Rulestates that electron orbitals that are______________________are first half-filled before they are totally filled.

1s 2s 2p 3s

1s 2s 2p


14/19

EXAMPLE 1:Give the electron configuration for each of the following elements and its ion. For the ion, state if it is

paramagneticor diamagnetic:

a. Cu

Cu+

b. Mn

Mn5+


15/19

QUANTUM NUMBERS OF AN ATOMIC MODEL

An atomic orbital is characterized by threequantum numbers.

The__________________quantum number deals with the atomic orbitals size and energy. It tells us the relative distance

of the electron from the nucleus. It uses the variable___________ and provides the shell number of the electron.

EXAMPLE:Calculate the principal quantum number of each atomic sublevel.

a. 6s b. 3p c. 8f d. 5d

The electron capacity of each shell can be determined by using the formula:____________________ .

Electron Shell (n) Maximum Number of Electrons

1

2

3

4

The_______________________quantum number deals with the shape of the atomic orbital. Each atomic orbital has aspecific shape.

It uses the variable___________ and formula_______________________.

Each atomic sub-level has an L value associated with it.

Sublevel s p d f g

L value 0 1 2 3 4


16/19

The________________________________quantum number deals with the orientation of the orbital in the space around

the nucleus. It is a range of the previous quantum number: -l to +l. It uses the variable___________.

Sublevel s p d f

L value 0 1 2 3

MLvalue

The____________quantum number (mS) helps to discuss the rotational spin of the electron and is_______and_______.

EXAMPLE: What l or mlvalues are allowed if n = 3? How many orbitals exist for n = 3?

EXAMPLE:How many electrons can have the following quantum sets?

a) n = 4

b) n = 3, l = 1

c) n = 4, mL= -2

d) n = 5, l = 2, mL= -2


17/19

EXAMPLE:Give the set of four quantum numbers that represent the indicated electron in each of the following elements.

a. P(13thelectron) n = , l = , ml= , ms=

b. Ni2+(23rd electron) n = , l = , ml= , ms=

c. Cr3+(21stelectron) n = , l = , ml= , ms=


18/19

ELECTRON SHIELDING

When looking at any particular electron within an atom it experiences two major forces.

A(n)________________force from the nucleus and a(n)_______________force from the surrounding electrons.

Now the electron can become shielded from the full force of the nucleus because of the other surrounding electrons.

_________________________________(Zeff) measures the force exerted onto an electron by the nucleus, and

can be calculated using______________Rule.

EXAMPLE 1:Answer the following questions dealing with the indicated orbitals.

A) 1s B) 4f C) 3s D) 3d E) 2p

i. In which orbital below would an electron (on average) be farthest from the nucleus?

ii. In which orbital below would an electron (on average) be closest to the nucleus?

+2

e-

e-

e- e

-

e-

Zeff= Z S

Z =

S =


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MCAT Chapters 1 & 2

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Transcript of MCAT Chapters 1 & 2