DECEMBER 6_2007 REVIEW CLASS
ALL QUESTIONS FROM CHRISTMAS
ASSIGNMENT.
#6) If the atom has an atomic number of 11 (given), it has 11 protons
and a nuclear charge of 11+, choice 1
#7) The atomic number is always the number of protons alone, the
answer is 35 as the question mentioned 35 protons.choice
#11) Most small atoms have at least one neutron per proton. Sodium
has 11 protons and thus must have at least 11 neutrons. The best
choice is 4, mass # 23 (11 protons and 12 neutrons)
#14) Cobalt-58 has an atomic number of 27(periodic table or table
S) and a mass number of 58. Subtract the mass number from the
atomic number any you get 31 neutrons. Choice 1 has 27 protons and
31 neutrons
#15) 12C and 14C both have the same atomic (6) number as they are
the same element. 12C has 6 neutrons and 6 protons, 14C has 6 protons
and 8 neutrons choice 3 states that 14C has more neutrons.
#17) Eliminate choices 1 and 4 because C does not have a mass
number anywhere near 35. Choice 2 is incorrect as it would give a
weighted average of exactly 36. The correct choice is # 3, closest to
35 which is the most heavily weighted mass number.
#18) Choice 3, multiply each isotopes mass number by its percentage
/100. Add the result for all the isotopes.
#21) According to the periodic table , the electron configuration of Al
is 2-8-3. The second shell has 8 electrons, which is more than the 2
in shell one and the 3 in shell 2.
#23) The third energy level (shell, principle quantum #) can hold a
maximum of 18 electrons (2n2) , 2(3)2 equals 18.
#27) Choice three is the only one in which an inner shell is not filled.
The 2-7-1 is the excited state of the ground 2-8.
#29) The excited state of N must:
1) Have exactly 7 electrons.(atomic #7 = 7 electrons neutral atom)
2) Have a configuration with an inner shell with fewer electrons
than ground.
Choice 2 (2-4-1) has only 4 second shell electrons, the ground has
(2-5 from periodic table) --- the ground state does not have the
electron in the third shell. Choice 2 also has the 7 electrons of
neutral nitrogen. Choice 3 has 8 electrons and thus is not neutral
nitrogen. Choice 4 has only 6 electrons and choice one is the ground
state.
#33) Emission occurs during fallback from an outer energy level or
sublevel to an inner energy level (or sublevel). In this case the
electron falls from the 2p down to the inner 1s and releases energy
(emission spectra)
#38) Metals are good conductors, have metallic luster, malleability
and are on the left of the metalloid line on the periodic table. Non
metals are poor conductors, are brittle and do not show luster. Br is
described by the later situation. Also you must remember Br is a
liquid at STP.
#45) Metals are atoms from the left of the metalloid line of the
periodic table, Au is such an element.
#45 Choice 4, all are in the same group (2). Be careful as they skip
some of the elements to throw you!
#53) Non-lustrous brittle solids are nonmetals. Group 16 has
nonmetals with six valence (outer shell ) electrons.Choice 4 (either O
or S or Se). NOT Te(metalloid).
#57) P2O5 has subscripts that cannot be reduced, indicating that they
are the in the simple (empirical) ratio. All of the others can be
reduced and are not empirical.
#62) The mole ratio of CuSO4 to H2O is 1:5 therefore
CuSO4 = 1
H2O
5
= 0.250
X
#63) (NH4)2HPO4
X = 5(0.250) = 1.25 mol (choice A)
H=9, N=2, O=4, P=1 mole(s)
8 + 1= 9 moles H
64) Because ozone has a molar mass of 48 and oxygen has an atomic
mass of 16, the formula of ozone must be O3,therefore there are 3
moles of oxygen.
#66) The molar mass of LiF is
Li
1
x 7g/mol
F
1
x 19g/mol
MOLES = MASS/MOLAR MASS
26 g/mol
MOLES = 39/26 = 1.5 mol LiF
#68) Assume a 100 gram sample, convert % to grams. Convert each
to moles and divide by smallest mole quantity.
S: 40g/32g/mol = 1,25 mol / 1.25 = 1 mol S
O: 60g/16g/mol = 3.75 mol / 1.25 = 3 mol O choice 3, SO3
#71) 2Na + 2H2O  2NaOH + H2
Na
H2
2
1
=
4
X
GIVEN
X = 2 mol H2 choice 2
#74) 4 NH3 + 5 O2  4 NO + 6 H2O
NH3
H2O
4
6
=
2
X
GIVEN
4X =12
X = 3mol H2O choice 3
#78) N(g) + N(g)  N2(g) The 2 moles of N(g) BOND to form one
mole of N2 molecules, energy is ALWAYS released when bonds (or
attractions) are formed.
#76) 2 C2H2 + 5 O2  4 CO2 + 2 H2O
C2H2
O2
2 =
5
0.5 mol
X
2X =2.5
X = 1.25 mol O2 choice 3
CONVERT YOUR 1.25 MOLE OF OXYGEN INTO
GRAMS, THE UNITS ASKED FOR.
MOLES = MASS/MOLAR MASS
1.25 = MASS/32 G/MOL
MASS = 40 G OXYGEN
#77) Cu
+ 4 HNO3  Cu(NO3)2 + 2 H2O + 2 NO2
STEP ONE, convert your given ( 32 g of Cu) to moles.
MOLES = MASS/MOLAR MASS
MOLES = 32/63.5 g/mol = 0.50 mol Cu
Cu
H2O
1 =
2
0.5 mol
X
X =1
X = 1 mol H2O
Convert the 1 mol of water to grams, the units asked
for.
MOLES = MASS/MOLAR MASS
1 mol H2O = MASS/ 18 g/mol = 18 g WATER