DECEMBER 6_2007 REVIEW CLASS

ALL QUESTIONS FROM CHRISTMAS ASSIGNMENT.

#7) The atomic number is always the number of protons alone, the answer is 35 as the question mentioned 35 protons.choice

#6) If the atom has an atomic number of 11 (given), it has 11 protons and a nuclear charge of 11+, choice 1

#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!

#62) The mole ratio of CuSO4 to H2O is 1:5 therefore

CuSO4 = 1 = 0.250 X = 5(0.250) = 1.25 mol (choice A)H2O 5 X

#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.

#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).

#63) (NH4)2HPO4 H=9, N=2, O=4, P=1 mole(s)

8 + 1= 9 moles H

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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

26 g/mol

#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

MOLES = MASS/MOLAR MASS

Li 1 x 7g/mol

F 1 x 19g/mol

MOLES = 39/26 = 1.5 mol LiF

#71) 2Na + 2H2O 2NaOH + H2

Na 2 = 4 H2 1 X X = 2 mol H2 choice 2

GIVEN

#74) 4 NH3 + 5 O2 4 NO + 6 H2O

NH3 4 = 2 4X =12 H2O 6 X X = 3mol H2O choice 3

GIVEN

#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 2 = 0.5 mol 2X =2.5 O2 5 X X = 1.25 mol O2 choice 3

CONVERT YOUR 1.25 MOLE OF OXYGEN INTO GRAMS, THE UNITS ASKED FOR.

1.25 = MASS/32 G/MOL

MOLES = MASS/MOLAR MASS

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.

Cu 1 = 0.5 mol X =1 H2O 2 X X = 1 mol H2O

Convert the 1 mol of water to grams, the units asked for.

MOLES = MASS/MOLAR MASS

MOLES = 32/63.5 g/mol = 0.50 mol Cu

MOLES = MASS/MOLAR MASS

1 mol H2O = MASS/ 18 g/mol = 18 g WATER