Chemistry Mid-term Review
Three samples of 1.12g, 1.8g, and 1.562g are mixed together. The combined mass of the three samples, expressed to the correct number of sig figs would be
4.5gs
The label on a tube of toothpaste tells you it contains "the most whitening power of any tooth paste on the market" What would be the best way for you to start to evaluate this claim
Research what ingredients actually whiten teeth and see if the toothpaste contains one of those ingredients
Which of the following does not have eight valence electrons
SR+
Which of the following is an example of qualitative data: The pH of a liquid was 5, Salt crystals formed as the liquid evaporated
Salt crystals formed as the liquid evaporated
a property that depends on the extent or size of a system
extensive property
describe the properties of a liquid
low KE particles move but are still close, they move around each other
If a material can be shaped or extended by physical pressure, such as hammering which property does the material have
malleability
how mendeleev's periodic table organized
mass and chemical/ phyiscal properties
The average atomic mass of an element
may not always equal the mass of any isotopes
The idea of arranging the elements in the periodic table according to their chemical and physical properties is attributed to
mendeleev
The actual numerical charge on an electron was determined in the
millikan oil drop experiment
a student recorded the following while completing an experiment Color of substance: yellow, shiny powder Effect of magnet: yellow, shiny powder was attracted The student should classify this substance as a
mixture
The chemical formula for water, a covalent compound, is H2O The is formula is an example of
molecular formula
in oxides of nitrogen, such as N2O, NO, NO2, N2O3, atoms combine in small whole-number ratios. This evidence supports the law of
multiple proportions
a nuclear particle that has about the same mass as a proton, but with no electrical charge is called
neutron
Name the compound Ni(CIO3)2
nickel (II) chlorate
The discovery of what elements added a new column to Mendeleev's periodic table
noble gases
A bond that is less than 5% ionic is considered
nonpolar covalent
what is atomic number
number of protons on periodic table
When determining the size of an atom by measuring the distance between bonded, identical, adjacent nuclei, the radius of an atom is
one-half the distance between nuclei
multiple covalent bonds may occur in atoms that contain carbon, nitrogen, or
oxygen
Most chemical bonds are
partly ionic and partly covalent
(is this a physical or chemical change) iron melting
pc
The horizontal rows an the periodic table are called
periods
the periodic table
permits the properties of an element to be predicted before the element is discovered
A quantum of electromagnetic energy is called
photon
can be observed with out changing the identity of a substance
physical change
Iodine monochloride (ICl) has a higher boiling point than bromine (br2) partly because iodine monochloride is
polar molecule
If the atoms that shared electrons have an unequal attraction for the electrons, the bond is called
polor
A chemist obtained the values 5.2246g, 5.2353g, and 5.2501g for the mass of sample. With out knowing the true mass of the sample, it can be said that these values have
poor precision
Mendeleev left spaces in his periodic table and predicted the existence of three elements and their
properties
what is mass number
protons + neutrons
max Planck proposed that a hot object radiant energy in small, specific amounts called
quanta
A numerical result is said to have good precision it
repeated measurements agree closely
A theory is accepted as the explanation of an observed phenomenon until
repeated observations conflict with theory
Because a few alpha particles bounced back from the foil, Rutherford concluded that they were
repelled by densely pack regions of positive charge
Chemist once theroized that a molecule that contains a single bong and double bond split its time existing as one of these two structures, this effect became known
resonance
The electrons available to be lost, gained, or shared when atoms form compounds are called
valence electrons
Under ordinary conditions of temperature and pressure, the particles in a gas are
very far from one another
The only pure substance listed below is: bread dough, vinegar, vitamin C, sea water
vitamin C
what is an extensive property of matter
volume
The distance between two successive peaks on adjacent waves is its
wavelength
what happens to the frequency of a wave if the wavelength decreases
wavelength decreases frequency increaes
what is the atomic mass
weighted average of all natural occuring isotopes
what is an example of an intensive property of matter
desity
The equal but opposite charges present in the two regions of polar molecule create
dipole
all of the following are steps in the scientific method except: Observe and recording date, forming a hypothesis, discarding data inconsistent with the hypothesis, developing a model on experimental resulting
discarding data inconsistent with hyopothesis
In metallic bonds, mobile electrons surrounding the positive ions are called
electron sea
A measure of the ability of an atom in a chemical compound to attract electrons from another atom in the compound is called
electronegativity
What are two types of pure substances
element and compound
The changes of an atom from an excited state to the ground state always requires
emission of electromagnetic radiation
Using a metric ruler with 1mm divisions , the sides of a rectangular piece of plywood were measured as 3.54cm and 4.84cm, which corresponds to an area of 17.1690 cm^2. Which of these show the area expressed
17.2 cm (sig fig rules)
a single orbital in the 3d level can hold ___ electrons
2
The number of sig figs in the measurement 0.0320g is
3
When 64.4 divided by 2.00 the correct number of sig. figs in the result is
3
how many extra electrons are in the lewis structure of the phosphate ion PO4 3-
3
The product of 13cm and 5.7 is correctly reported as
74 cm
How many electrons must be shown in the Lewis structure of the hydroxide ion OH-
8
In molecule of fluorine, the two shared electrons give each fluorine atom how many electrons in the outer energy level
8
Carbon-14 (atomic number 6) the radioactive nuclide used in dating fossils has
8 neutrons
Which of the following is not an example of a molecular formula: B, O2
B
Based on the octet rule, boron will most likely form a ____ion
B3-
Bromine is much more apt to exist as an anion that is potassium This is because___
Bromine has a greater electron affinity than potassium does
What is the formula for the compounds formed by calcium ions and chloride ions
CaCl2
Dalton supported his atomic theory with experimental evidence. What experiment would have supported the postulate that in chemical reactions, atoms are combined, separated, or rearranged
Dalton observes combustion in a closed chamber, nothing that the mass is the same before and after the reaction although the products looked quite different
Which of these is not an example of a SI base unit: Kelvin, Liter
Liter
The substance whose Lewis structure shows three covalent bonds is
NH3
what is the relationship between isotopes, mass number, and neutrons
Neutrons help to make up the mass number (p plus n) and isotopes are elements with different mass numbers
Which atom has the smallest number of neutrons
Nitrogen-14 (mass number - #of protons)
You find an unknown substance that cannot be separated by filtration, evaporation, or distillation. Would the explanation that this substance is an element be scientifically valid
No, because the substance could be a compound, which also cannot be separated by physical means
(is this a physical or chemical change) pencil breaking into 2
P.C
In one experiment, magnesium metal is melted. In the second, magnesium metal is burned. Classify the change in each experiment as chemical or physical
The change is physical because the substance is still magnesium but it is just melted so the identity has not changed. In the second experiment, the change is chemical. the identity of the magnesium is gone because it is burnt
a compound is
a substance, made of two or more atoms that are chemically bonded, that can be broken down into simpler stable sunstances
Use VSEPR theory to predict the shape of carbon dioxide CO2
`linear
a chemical change occurs when
a leaf changes color in the fall
A polar molecule contains
a region of positive charge and a region of negative charge
A homogeneous mixture is also called
a solution
To appear shiny a material must be able to
absorb and re-emit light of many wavelenfths
Which of the following is an example of a homogeneous mixture: air, orange juice, raw milk, marble
air
A chemical can be defines as
any substance that has a definite composition
Moseley's work led to the realization that element with similar properties occurred at regular intervals when the element were arranged in order of increasing
atomic number
how was mosely's organized
atomic number and nuclear charge
Why do chemists work with moles instead of individual atoms
atoms are really really tiny, and avagdro's number is a really large number so a lot of atoms fit into a mole and that makes it easier to measure
Because most particles fired at metal foil passed straight through, Rutherford concluded that
atoms were mostly empty space
which of the following is not a physical change: grinding, cutting, boiling, burning
burning
how is the modern periodic table organized
by increasing atomic number
(is this a physical or chemical change) milk souring
cc
(is this a physical or chemical change) silver tarnishing
cc
The metric unit length that is closet to the diameter of a pencil is the
centimeter
the electrostatic attraction between positively charged nuclei and negatively charged electrons permits two atoms to be held together
chemical bond
changes the identity of a substance
chemical change
In the three molecules, O2, HCl and F2 what atom would have a partial negative charge
chlorine
The ions in most ionic compounds are organized into a
crystal
As atoms bond with each other
decrease their potential energy , thus creating more-stable arrangements of matter
in a row in there periodic table as the atomic number increases the atomic radius generally
decreases
The element that has the greatest electronegativity is
fluorine
a physical change occurs when a
glue gun melts a glue stick
If electrons in an atom have the lowest possible energies, the atom is in the
ground state
Compared with ionic compounds, molecular compounds
have lower melting points
In the alkaline-earth group atoms with the smallest radii
have the highest ionization energies
describe the properties of a gas
high KE particles separate and move throughout the container can fill a space but not run in to the same particle
If a mixture is uniform in composition, it is said to be
homogenous
consider the following postulates of dalton's atomic theory i. Each element is composed of extremely small particles called atoms ii. atoms are indivisible iii.atoms of a given element are identical iv. Atoms of different elements are different and have properties Which of the postulates is(are) no longer considered valid
ii. and iii.
a property that does not depend on the amount of matter present, such as pressure, temperature, or density
intensive property
how are frequency and wavelength related
inversely- can't change wavelength without changing frequency
The greater the electronegativity difference between two bonded atoms, the greater the percentage of ____ in the bond
ionic character
The energy required to remove an electron from an atom is the atom;s
ionization energy
Name the compound Fe(NO3)2
iron (II) nirate
In drawing a Lewis structure, the central atom is generally the
least electronegative atom
a state of matter in which a material has no definite shape but has a definite volume is the ____ state
liguid
Explain nuclear charge and how is affects the general trend in radii of atoms of elements going from left of right across a period in the periodic table
look on ipad
describe the properties of a soild
low K.E fixed shape and volume particles can vibrate but can't move
In groups 13 through 18, valence electrons may be in sublevel
s and p
what orbitals do electrons occupy
s and p
Compared with nonmetals, the number of valence electrons in metals is generally smaller
smaller
Use VSEPR theory to prdict the shape of the carbon tetraiodide molecule Cl4
tetrahedral
The major difference between a 1s orbital and 2s orbital is that
the 2s orbital is at a higher energy level
Cathode rays are deflected away from negatively charged plate because
the are negatively charged particles
An atom is electrically neutral because
the number of protons and electrons are equal
Which of these statements about y=kx, is not true
the product of y and x is constant
which model of atom explains the orbitals of electrons as waves
the quantum model
according to the law of definite proportions any two samples of KCl
the same ratio of elements
According to the particle model of light, certain kinds of light cannot eject electrons from metals because
the wavelength of the light is too short
A line spectrum is produced when an electron moves from one energy level
to a lower energy level
Use VSEPR theory to predict the shape of the chloride ion ClO3-
trigonal pyramidal
the noble gases were, until relatively recently thought to be entirely nonreactive. Experiments in the early 1960's showed the Xe could in fact form compounds with fluorine. The formation of compounds consisting of Xe is made possible by
xenon's relatively low ionization enegry
What is true about the y=kx
y is directly proportional to x, x is a variable, the graph of y versus x is a straight line
