Chemistry General Midterm
The temperature of a sample of water changes from 10 C to 20 C when the sample absorbs 418 joules of heat. What is the mass of the sample
10 g
A student determined the heat of fusion of water to be 88 calories per gram. If the accepted value is 80. calories per gram, what is the student's percent error?
10%
What is the gram formula mass of Li2SO4?
110
At 1 atmosphere of pressure, 25 grams of a compound at its normal boiling point is converted to a gas by the addition of 34,400 Joules. What is the heat of vaporization for this compound, in Joules per gram?
1376
Given the unbalanced equation __Al + __CuSO4-->___Al2(SO4)3 + ____Cu When the equation is balanced using the smallest whole-number coefficients, what is the coefficient of Al?
2
Which principal energy level (shell) can hold a maximum of eight electrons
2
What is the approximate percent composition by mass of CaBr2 (formula mass=200)
20% calcium and 80% bromine
When 200 grams of water cools from 50 to 25 the total amount of heat energy released by the water is
21
Which notations represent different isotopes of the element sodium?
22Na and 23Na
The percent composition by mass of magnesium in MgBr2 (gram-formula mass=184 grams/mole) is equal to
24/184 x 100
What is the gram-formula mass of Fe(NO3)3
242 g/mol
Which equation shows conservation of atoms
2H2 + O2 --->2H2O
What is the mass number of a ^3 1H atom?
3
What is the total number of different elements present in NH4NO3?
3
An ion that consists of 7 protons, 9 neutrons, and 10 electrons has a net charge of
3-
What is the total number of neutrons in an atom of ^57/26 Fe?
31
What is the total number of valence electrons in an atom of germanium in the ground state?
4
What is the percent by mass of oxygen in Ca(OH)2 [formula mass=74.1]
43.2
The diagram below represents a portion of a triple-beam balance [insert picture of balance] If the beams are in balance with the riders in the positions shown, what is the total mass of the object?
545.20 g
In an experiment using a calorimeter, the following data were obtained: Mass of calorimeter + water.... 150g Mass OD Xloeimwrwe.......100g Final temperature of water....55 C Initial temperature of water.... 25 C What is the total number of Joules absorbed by the water?
6300
What is the pressure of a mixture of CO2, SO2, and H2O gases, if each gas has a partial pressure of 25 kPa?
75 kPa
The temperature of 30. K expressed in degrees Celsius is
-243 C
What is equivalent of 0 Kelvin and on Celsius scale?
-273 C
The diagram below shows the upper part of a laboratory burner [insert picture of flame-labeled A B C D] Which letter represents the hottest part of the burner
C
What is the empirical formula for a compound with the molecular formula C6H12Cl2O2?
C3H6ClO
What is the molecular formula of a compound that has a molecular mass of 54 and the empirical formula C2H3?
C4H6
Which is an empirical formula?
CH
Which sample of CO2 has a definite shape and a definite volume?
CO2(s)
Which substance can be broken down by chemical means?
Cu
At STP, which gas will diffuse more rapidly than Ne?
He
A cube of iron at 20 C is placed in contact with a cube of copper at 60. Which statement describes the initial flow of heat between the cubes?
Heat flows from the copper cube to the iron cube.
Which statement best describes a chemical property of silicon?
Silicon reacts with fluorine
A mixture of crystals of salt and sugar is added to water and stirred until all solids have dissolved. Which statement best describes the resulting mixture?
The mixture is homogeneous and cannot be separated by filtration
Which atom in the ground state has a partially filled second electron shell?
lithium atom
Which physical changes are endothermic
melting and evaporating
Which particle has no charge
neutron
Compared to an atom of phosphorus-31, an atom of sulfur-32 contains
one more proton
What is the name of the polyatomic ion in the compound Na2O2?
peroxide
Which subatomic particles are located in the nucleus of a carbon atom?
protons and neutrons
Given the balanced equation 2KI+F2--->2KF + I2 Which type of chemical reaction does this equation represent?
single replacement
What is the chemical name for Na2SO3
sodium sulfite
When the electrons of an excited atom return to a lower energy state, the energy emitted can result in the production of
spectra
In which process does a solid change directly into a vapor?
sublimation
Which process occurs when dry ice, CO2(s), is changed into CO2(g)
sublimation
The valence electrons in an atom of phosphorous in the ground state are all found in
the first shell
Which process increases the potential energy of the particles of a sample
vaporization
Which pair consists of a molecular formula and its corresponding empirical formula?
P4O10 and P2O5
How do the energy and the most probable location of an electron in the third shell of an atom compare to the energy and the most probable location of an electron in the first shell of the same atom?
In the third shell, an electron has more energy and is farther from the nucleus
Which particle has a mass that is approximately equal to the mass of a proton?
a neutron
Which type of matter can not be broken down into simpler substances by a chemical change?
an element
Which quantity represents the number of protons in an atom
atomic number
Which polyatomic ion contains the greatest number of oxygen atoms?
carbonate
Which change occurs when an atom in an excited state returns to the ground state?
energy is emitted
At the same temperature and pressure, 1.0 liter of CO(g) and 1.0 liter of CO2(g) have
equal volumes and the same number of molecules
Recovering the salt from a mixture of salt and water could best be accomplished by
evaporation
