chem 260 (exam 1)

Chemistry 260 with Chen at University of Michigan - Ann Arbor

About this deck

By: Neelam Gire
Textbook:

Principles of Modern Chemistry, Sixth Edition
Created: 2012-01-31
Size: 51 flashcards
Views: 73

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The law of conservation of mass

In a chemical reaction, matter cannot be created or destroyed.
mass of products = mass of reactants

The Law of definite proportions or constant composition (Joseph Proust)

All samples of a given pure compound, regardless of their source or how they were made always contain same elements in the same parts (fraction) of mass.

The Law of Law of multiple proportions (John Dalton)

when two elements A and B, react to form more than one compound, the different masses of B that combine with a fixed mass (1g) of A can be expressed as a ratio of small whole numbers.

The atom

-smallest particle of an element.
-splits into subatomic particles.
such as: electrons (-ve), protons (+ve) and neutrons (neutral)
-concept of splitting atom started with discovery of: cathode rays, x-rays, the electrons.

The electron (J.J Thompson)

Discovered the electron while working on his cathode ray experiment.
proposed that cathode rays consist of tiny negatively charged particles, which we now call electrons.
measured the charge: mass ratio of the electron.
mass/charge = -1.76x10⁸ coulombs.

The electron (Robert Millikan)

used the oil drop experiment to calculate the charge on a single electron.\
charge on any drop was always a whole number multiple of -1.6022x10^-19 coulombs.
further calculated the mass of an electron to be 9.10x10^-28 g.

The atomic model

J.J Thompson proposed the "plum pudding" or "chocolate chip cookie" model of the atom.
atoms consists of diffused cloud of positive charges and electrons are embedded randomly in it.

Radioactivity

Henri becquerel and the curies ( Marie and Pierre) discovered and studied radioactivity.
3 types of rays produced: alpha (+ve), beta (-ve) and gamma (no charge).

Ernest Rutherford (1871-1937)

used alpha particles to study the inner structure of gold atom.
beam of dense, positively charged alpha particles emitting from radium was aimed at thin gold foil.
demonstrated the existence of a positively charged nucleus, a dense central core within the atom.

Rutherford's nuclear atom

majority of the particles penetrated the foil undeflected.
a few particles were deflected.
occasionally a very few particles were deflected at very large angles.
thus he proposed nuclear atom of the atom.
an atom consists of a tiny massive center of positive charge (the nucleus) surriunded by electrons, which are moving around the nucleus.

Atomic no. (Z)

no. of protons in the nucleus of an atom.
determines the chemical identity of an atom.

Mass no. (A)

= no. of protons + no. of neutrons= atomic no. + no. of neutrons.

Atomic mass

weighted average of the masses of the isotopes of the element.
masses of atomic particles expressed in atomic mass unit (u).
mass of isotope 1 in amu) x (% abundance isotope1/100)

Mendeleev"s periodic table

Dmitri Mendeleev.
listed the elements in order of their atomic masses and found that elements with similar chemical properties fell in the same column.
proposed table base on observation supported by scanty understanding.

isotopes

atoms with same atomic no. but different mass nos.

The periodic law

Fundamental basis of the periodic table is atomic no. rather that atomic mass.

Modern periodic table.

known elements are arranged in order of increasing atomic no. (z).
each element is represented by its symbol and atomic mass.

Periodic table contains

8 principle columns called groups (also called families) and 7 main horizontal rows called periods.
elements can be classified as metals, non-metals, metalloids or semi-metals.
main group elements- A
transition elements or metals- B

metals

-mostly solids
-good electrical conductors.
-good heat conductors.
-lustrous (shiny)
-malliable and ductile
-lose electrons during chemical change.

non-metals

-many are gases
-poor conductors or non-conductors
-poor heat conductors
-dull in appearance
-brittle
-gain electrons during chemical change.

atomic structure

atoms

molecule Ions

diatomic polyatomic polyatomic monoatomic

Molecules

Groups of atoms in which one or more pairs of electrons are shared between bonded atoms.
diatomic: H₂ , N₂ , F₂, HCl and CO
polyatomic: H₂ O, NH₃, CH₄,

Ions

An atom or groups of atoms with a net positive or negative charge.
monatomic: Na⁺, S^2-
polyatomic: OH^-, NH₄

Cations

an ion with positive charge.
formed when an atom looses one or more electrons.

anions

an ion with negative charge.
formed when an atom gains one or more electrons.

A mole: a chemist's dozen

Latin word meaning "a huge pile".
amount of any substance that contains the same no. of entities (atoms, molecules or ions) as there are in exactly 12g of carbon-12 isotopes.
1 mole of atoms=6.022x10²³ atoms=avogadro's no. (N_A)

chemical bonds (ionic bond)

transfer of one or more elements between a metal and a non-metal.

chemical bonds (covalent bond)

sharing of a pair or more of electrons between non-metals.

Elements (atomic element)

exist in nature
basic unit=atom
O, Na, Cl, F

elements (molecular elements)

exist in nature
basic unit=molecule
diatomic molecules : H₂, O₂
polyatomic: P₄, S₈

compounds (molecular compounds)

two or more elements covalently combined.
basic unit=molecules
H₂O, NH₃

compounds (ionic compound)

contains cation and anion held by electrostatic forces
basic unit=formula units
NaCl, KBr, CaCl₂

Formula mass

sum of atomic masses of all atoms in its chemical formula.

Chemical formula

molecular formulas.
shows the no. of atoms of each kind in one molecule of the compound.

Molar mass of compounds

mass in grams of 1 mol of a compound (molecules or formula units).

molar mass

sum of the atomic masses of all the atoms in its chemical formula.

theories

unifying principles that explain observations and the laws based on them.
-help understand natural world.
-framework for organizing scientific knowledge.

laws

A concise verbal or mathematical statements about consistently observed phenomenon.

accuracy

closeness of measured value to true value or acceptable value.

precision

multiple measurements give nearly identical values.

controlling the no. of digits or significant figures

rule:
-any non-zero digit is significant. eg. 1.52g (3 sig. fig.)
-zeroes between non-zero digits are always significant. eg. 1.08km (3 sig. fig.)
-leading zeroes. eg. 0.0045kg (2 sig. fig.)
-trailing zeroes. eg. 4.000g (4 sig. fig.)

exact nos.

-A dozen of eggs
-no. in a room
-20 pennies

measured nos.

involves an estimate.

Observations

Are quantitative and qualitative

quantitative measurements

mass (kg)
length (m)
time (s)
temperature (kelvin,k)
m³ (volume)
kg/g³ or g/cm³ (density)

methods of separating mixtures

-decanting
-filtration
-distillation
-crystallization

chemical changes

show altered composition or identity of substances.
eg. burning of gas or oil or wood.
-rusting
-dissolving a penny in nitric acid.

physical changes

show only altered state or appearance of substances
eg. boiling and freezing water.
-dissolving sugar in water.
-condensation of moisture on a cold surface.

hypotheses

tentative explanation or prediction concerning some phenomenon. (educated guess)
-a guess that can be tested by experiment.

chemistry

study of matter and its transforation.
-central to our understanding of diverse disciplines in science and engineering.

matter

atomic view
-consists of atoms and molecules (the particulate level)
-anything in universe that has mass and takes up space.

About this deck

By: Neelam Gire
Textbook:

Principles of Modern Chemistry

Principles of Modern Chemistry, Sixth Edition
Created: 2012-01-31
Size: 51 flashcards
Views: 73

About StudyBlue

“I have used this website for three exams, and I see a huge difference in my test results.”
Naj