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Answers to 2-column Review Sheet
1. Pick the set that has the same # of Protons for both atoms. Reason: The only thing atoms of the same element HAVE
to have in common is the number of protons!
2. B is the answer -- Reason: remember that the LOWER number is the atomic # which is the # OF PROTONS -- the only
thing that truly identifies an atom of an element. Each atom of sulfur MUST have 16 protons. The top # is the MASS -that's the protons + neutrons. 16 protons + 17 neutrons (from the problem) = 33; the top # for B.
3. Check out your Chemistry book, Appendix B4 around pages R50 - R51 . They're in the back of your book.
4. B is the answer: Best way to figure this out: look Ca up on the P.Table and write out the electron configuration
yourself! PS -- If you read all the answers carefully, you will find they are written so the all show 20 electrons -- don't
rely on counting up electrons! Make sure you can write the configurations using the s, p & d block information yourself!
5. You actually drew this in your notes.
A is where the electron gains
energy and moves to a higher
energy level (farther away
from the nucleus)
A
When B happens, the extra energy is given off as
the spectral lines like we saw in class
B
B is where that same electron
gives off energy as it goes back down t
to a lower energy level (closer to the nucleus)
6. I gave you a Bohr Model Diagram that you put in your notes. According to that, A) 410 nm (nano-meters) is the best
answer.
7. Notice that this number has an * next to it -- when I wrote this review we had not gotten to this yet and I didn't know
if we would. However, we did and you received a decay chart when we were working with the laptops learning about
radiation. You could create something like this:
 emission
 emission
U-232
Np-232
Pa-228
Reasoning: The idea is for you to remember that in a beta emission a neutron is changed into a proton. This changes
the element (ahead one on the PTable) but not the mass (the proton & neutron weigh the same and just got traded out
one for the other)
In an alpha emission the atom loses 2 protons (go back 2 on the PTable) AND 2 neutrons. This changes the MASS down
by 4. In my example 232 (the mass of Np) - 4 = 228 (the mass of Pa).
8. D) .125g is the best answer. Reasoning: For every 20 minutes you're left with 1/2 of what you had before & there are
3 sets of 20 mins. in 1 hour. So, starting with 1 g, after 20 min you will have .5 g; then after another 20 min. you will
have 1/2 of that = .25g; then after the last 20 min you are left with 1/2 of .25g = .125 g.
9. The strongest bond is covalent because shared electrons keep atoms together the best. Metallic bonds are next
strongest with ionic bonds (transfer of electrons) being the weakest (water can pull them apart)
10. D is the best answer. Again, we will cover this when you get back but with some simple reasoning you might see
that EN means the energy needed to break the bonds between the atoms and that CaCl2 is a salt (metal to non-metal),
also known as an ionic compound; that leaves your choices at either C or D. What you will learn is that ionic bonds are
considered weaker than their counterpart, covalent bonds (we've been calling them "not-salts") and so D is actually the
only setup that shows CaCl2 as an ionic cmpd whose bonds are weaker than the other molecule.
11. You need to know 2 things to do this: A) our 'salts' (metal to non-metal) are known as IONIC ('not-salts' are
therefore covalent) and B) how to figure out (or find) charges.
Rb + F would be RbF/ionic Reasoning: Rb is in the 1st column and has 1 valence electron that it loses to be Rb +1.
Fluorine is in column 17 that has 7 valence electrons and it gains one to be F -1. Criss-Cross
the 2 together to get RbF. Since it is a metal/non-metal combination, it is ionic.
C-4 + H would be CH4 /covalent Reasoning: the charge on the C is given and H is in the first column so with one
valence electron it has a charge of +1. Criss cross the 2 and it takes 4 H to cancel out
the C. Neither C nor H are considered a metal so this shows a covalent bond.
S-2 + O wouldn't happen because they are both negative charges -- O is -2. Remember you need a positive & negative
charges so they cancel out!
Fe+3 + SO4 would be Fe2(SO4)2 / ionic Reasoning: The iron charge is given as +3 and the SO4 charge can be found on
the flip-defs I had you make or on a little chart you put in your notebook. (or,
maybe you actually REMEMBERED it as -2. Criss-Cross these and remember
to use the ( ) around a poly-atomic ion when there is MORE THAN ONE of it!
12. C is the best Reasoning: Na is in the first column so has a +1 charge. O has a -2 charge (always & forever) so a
criss-cross means you need 2 Na's for each O. Since it's metal to non-metal it's a 'salt'
which is more commonly called IONIC.
13. To do this you would have to look up all three of these in your book. We will be working with them on Thursday, Jan
7. Here's the answer: Weakest = London Dispersion Forces because the + & - sides of the atoms or molecules are
created by random electron movement. As randomly as the electrons move to form + and - sides they can randomly
move out of that formation.
Next is Dipole-Dipole forces. Most covalent molecules have + & - sides (as we shall see) that
are permanent, though weak. The positive side of one molecule is attracted to the negative side of another molecule
like weak magnets. Because those + & - sides are permanent they rank stronger than those caused randomly.
Strongest is Hydrogen Bonding. A H hanging out on the edge of a molecule (like on water, H2O)
is basically a proton because some other atom has hogged its 1 electrons. Protons ARE a positive charge that is
relatively stronger than any other + charges we've talked about. That H (proton -- + charge) latches on to whatever
negative sides of molecules are nearby -- like the O in another water molecule near it. It's like a strong magnet.
THIS INFO IS ON PG. 240 - 241 IN YOUR BOOK
14. Best answer = C. Reasoning: there's only one thing you need to know here; the stronger the intermolecular forces
(that means between molecules like the interstate runs between states) the longer or more likely the particles are going
to stick to each other in the solid state. Since Fluorine is the gas and they are both at the same temp & press (STP -standard temp & press) is has WEAKER intermolecular bonds than the Iodine.
15. You better be able to do these!
Copper II Chloride is CuCl2 Remember the II means Cu+2 and Cl is in group 17, always a negative 1 charge.
Sodium Phosphate is Na3PO4 Sodium is in group 1 and has a +1 charge and phosphate is a poly-atomic ion that I asked
you to memorize! it as a charge of -3.
Di-hydrogen monoxide is H2O. For 'not-salts' (covalent molecules) we name them using mono-, di, tri, etc. . . .
Di-hydrogen means 2 hydrogens (H2) & monoxide means one oxygen, so H2O.
Nitrogen tri-sulfide is NS3. This is another 'not-salt'. when there is no prefix it's understood to mean one. The
name could have been 'mono-nitrogen' but that's a mouthful. Tri means 3 and I know it's
just sulfur because of the -ide ending. If it was a poly-atomic ion the ending would be -ate.
16. A) is the best answer. Reasoning: Calcium is in group 2 with 2 valence electrons that it loses for a +2 charge. always,
no choices so NO ROMAN NUMERALS. It is a salt (metal to non-metal) AKA an ionic compound so the di, tri, stuff isn't
used. The ending is simply the name of the poly-atomic ion -- so, Calcium Hydroxide.
17. D is the best answer. Reasoning: Ionic compounds (salts) are electrolytes where Covalent compounds (non-salts)
are not electrolytes (they do not conduct electricity when dissolved in water -- remember the conductivity devise) so
automatically choices A & B are knocked out of the running. Water is considered a very polar molecule (it has a + & side). Since "Like dissolves like" means that polar substances dissolve other polar substances and the unknown DOES
NOT dissolve in water, it is NOT polar. It must be non-polar (no + & - ends). That leaves d) covalent & nonpolar.
18. Easy peasy, Lemon squeezy! I'm only going to list the group &/or period. If you picked elements that match those,
you win!
alkali metals -- any in group or column 1
alkali earth metals -- any in group or column 2
halogens -- any in group or column 17
Noble gases -- any in group or column 18
transition metals any in the 'd' block which covers groups 3-12, periods 4-7
any metals -- any to the left of the stair-step, not counting those immediately adjacent to (touching) the stair step.
any non-metals -- any to the right of the stair-step excepting those listed in the following group
metalloids: Boron Grp13/Per. 2; Silicon Grp14/Per.3; Germanium Grp14/Per.4; Arsenic Grp15/Per.4; Antimony
Grp15/Per.5; Tellurium Grp16/Per5; Astatine Grp6/Per17
19. B is the best answer. Reasoning: The number of protons is the atomic number and that tells which element it is. 8
protons is Oxygen. A non-metal in group 16.
20. Element 117 will fall in group 17 -- the halogens. Groups are also known as families because the elements in that
family share characteristics. Since element 117 will be a Halogen, it will likely have halogen characteristics -- a colored
gas at room temp. that is poisonous & it will have a 7 valence electrons & will need one more to be stable so it will most
likely have a charge of -1.
21. C is the best answer. Reasoning: Radius INCREASES as you go DOWN a column so if we want the largest radius it
would be one of the elements lower down on the PTable. That eliminates Sulfur and Chlorine. But, radius DECREASES
as you go ACROSS to the right on the PTable so you would want the one to the left of your choices.
22. Lowest electronegativity = K then Si then S and highest electronegativity = F. Reasoning: Electronegativity is the
ability to keep and hold electrons in a chemical bond. Atoms with small radius' do this best so electronegativity follows
a decline in radius. Largest radius = K, then Si, then S with F having the smallest radius. ALSO, F has the HIGHEST
electronegativity so the farther away from F, the lower the electronegativity. K is farthest, then Si, & S is closest.
23. Best answer is D. Reasoning: The perspiration on your skin evaporates to keep you cool. Evaporation requires
energy so it is ENDOTHERMIC and it gets the heat to evaporate the sweat from your overheated body. So, evaporation
removes the heat from your body to make you feel cooler. When you are sweating and you get caught in a breeze you
get colder because the moving air is better at evaporating the water off you.
24. Notice the *. You'll hear about this next Thurs. In short, 'Boiling occurs when the vapor pressure = atmospheric
pressure' That is, when the pressure of the atmosphere pushing down on the liquid is equal to the pressure of the liquid
escaping into the gas phase at the surface of the liquid. You actually drew this out -- check your notes from when we
made ice cream. Check out pgs. 392 - 395 in your book.
25. D is the best answer. Reasoning; Between minutes 6 -12 is a straight horizontal line. It is the first plateau which
means there is a phase change from solid to liquid. So melting is occurring.
26. Around 500 to 550 0C. Reasoning: You find the atmosphere they are asking about on the left (very hard to do since
you can hardly read the numbers) and move across the graph to the line at the far right that separated the liquid from
the gas phase. Where those 2 lines meet is where the substance changes phase -- in this case boiling; going from liquid
to gas. We'll do this graph with CO2 and I'll show you the parts. Check out pages 402-403 in your book.
27. I made a mistake, Cp(metal) is the real 'X' and you use this to look up what the metal is. This is a 'plug and chug'
problem -- plug the information into the correct places and chug through the problem to get the answer:
M1(T1)Cp(metal) = M2(T2)Cp(water)
8.8g (92 - 25) [Cp(metal)] = 15g (25 - 20)
mass
Temp
X
= mass Temp
metal
metal
H2O
H2O
8,8g (67) X
589.6 X
589.6
=
=
15 (5)
313.8
589.6
4.184J/g0C <== all these #'s came from the problem
Sp.Ht
H2O
4.184
X
= .5322J/g0C This is the Specific Heat of the Metal Used. You can Identify the metal used by
looking up this Specific Heat. It's easy to use the chart you'll be given (or for this you could've googled it) to find that
Titanium Metal has the closest Cp to .53.
28. D is the best answer. Reasoning: Lead (Pb) has the smallest specific heat at .129 J/g0C meaning it takes the least
amount of heat to raise one gram of it one degree. Iron (Fe) is .449 J/g0C; Copper (Cu) is .385 J/g0C; & Aluminum (Al) is
,897 J/g0C . All these take more energy to go up a degree than Pb.
29. Aluminum (Al) would have the smallest change in temperature because it requires the most heat to change that
temp. Just divide 1000 J by each of the specific heats and you'll see which goes up the most (largest #) and which won't
go up so high (smallest #).
30. D is the best answer Reasoning: Remember, particles that are cooled go slower which means their kinetic energy
decreases. Then the particles tend to come together or get closer which shows up as the balloon shrinking. We put
balloon in hot and cold water to show this.
31. When the temp. on a gas increases, the particles of that gas move faster and farther apart. There would still be the
same amount of gas (# of particles) but it would be more spread out making the gas LESS DENSE. Remember too that
when particles exert more pressure they must be moving faster (more KE) which again causes them to move farther
apart and be less dense than before.
heat
=====>
Both have 5 particles. Small balloon particles
going slower (smaller arrows) & Big balloon
particles going faster (bigger arrows). Big balloon particles also farther apart showing greater volume.
32. D is the best answer Reasoning: Since it ends above where it started, energy was put in making it ENDOTHERMIC so
neither A or B could be the answer. The energy change is the difference between where it starts and where it stops.
The reactants started at 80 kJ and the products were at 160 kJ. A difference of 80 kJ.
33. The answer should be in your notes. But take a look:
This is EXOTHERMIC
A catalyst speeds up a reaction by lowering
the amount of activation energy needed to
start the reaction. Shown on this in red.
activated complex
Activation
energy
enthalpy of the rxn
energy of
reactants
energy of products
34. D is the best answer. Reasoning: The test tube getting hot is the 'change in temperature' and bubbles is the sign
that a gas is forming. No precipitate, no change in color.
35. Sodium metal dropped into water. (I did this in class!)
2 Na(s) + 2 HOH(l) --> 2 NaOH(aq) + H2 (g) This is a single replacement rxn. How to know? Element + Compound!
Silver Nitrate solution added to Sodium Chloride dissolved in water.
AgNO3 (aq) + NaCl(aq) --> AgCl (ppt) + NaNO3 (aq)
This is a double replacement rxn. How to know? Compound +
another compound.
36. 2C4H10 + 13 O2 ---> 8CO2 + 10 H2O
you can do these:
N2 + H2 -----> NH3
If you can do this you are 24 karat golden. If you couldn't, make sure
Fe
+
O2
--------->
Fe2O3
[answers at the end of this paper]
37. a) This is an acid/carbonate reaction because you put HCl on a compound containing carbonate.
b) NaHCO3 + HCl ---> CO2 +
it's already balanced.
c) Sodium Chloride -- NaCl
d) 10.3 g of NaHCO3
X moles
=
H2O
__84g_
1 mol
+ NaCl
(acid + carbonate = carbon dioxide, water & a salt)
The right side of the equation is from the mole box. 84 is the molar mass from
the PTable set over 1 mole to MATCH UNITS
X = .123 moles NaHCO3
38. P4 + 5O2 --->
P4O10
change g of P to moles of P;
? grams of oxygen for 7.75 g phosphorous? 3 steps!
7.75 g P4 = __123.9 g_ (P is 30.97 but it's P4 so 30.97*4 = 123.9)
X mols
1 mol
X= .0625504439 moles P4 (do not round until the end)
use mole ratio in problem
to find moles of O2
.0625504439 mole P4 = __1 P4__ The numbers on the right come from the
X mol O2
5O2
coefficients of the balanced equation.
X = .3127522195 mol O2
change moles from 2nd step
to grams
.3127522195 mol O2
=
Xg
X = 10,0 g O2
39. a) moles of limestone CaCO3 =
b) moles of CO2 =
__1 mol O2__ The 32 g is the molar mass of O2 -32 g
1 oxygen = 16 but there are 2.
__70 g__ =
__100 g__ the set up on the right represents the molar mass
X mol
1 mol
of the calcium carbonate.
X = .7 mols CaCO3 [this is the 'whole']
14 L CO2 = _22.4 L_
X mol
1 mol
remember, 22.4 L of a gas at STP = 1 mol of that gas.
X = .625 mol CO2 [this is the part]
c) part -->
_.625 mol__
whole ---> .7 mol
=
89.29 %
40. a) empirical formulas: 56.3% P become 56.3 g P = _31g P_
X = 1.82 mol P
x mols
1 mol
43.62% O becomes 43.62g O = _16 g O
X = 2.73 mol O
X mols
1 mol
divide both mols by the smallest: P = 1.82 = 1
O= 2.73 = 1.5
P2O3 molar mass = 110
1.82
1.82
molar mass of true formula =
__220__ = 2;
multiply each subscript by 2 for a true formula of P4O6
WAS THIS TO MIND BLOWING FOR YOU? JUST MAKE SURE YOU KNOW WHAT AN EMPIRICAL FORMULA IS AND THAT
YOU CAN CALCULATE IT FOR SIMPLER FORMULAS LIKE: 36% Ca & 64% Cl or 67.6% Hg, 10.8% S & 21.6% S
(answers at the end)
41. A) whole = 10.10g
barium chloride = 8.5 g water = 10.10 - 8.5 = 1.6g
part
part
barium chloride % = 8.5g/10.1 g = 84.16%
water % = 1.6g/10.1g = 15.84%
B) 84.16% barium chloride (BaCl2) becomes 84.16 g BaCl2/ x mol BaCl2 = 208 g water/1 mol water; x =.405 mol BaCl2
15.84 % water becomes 15.84 g H2O/x mol H2O =
18 g H2O/ 1 mol; x = .88 mol water
divide each # mols by the smallest = .405/.405 = 1 BaCl2
Formula = BaCl2
.88/.405 = 2,17 (round to 2) water
2H2O
42. Concentration, Temperature, Surface Area, Nature of the Reactants, Catalyst
43. C is the best answer. Reasoning: A) increases the concentration and that increases # collisions B) adds energy and
makes more collisions C) bigger pieces DECREASE the number of particles that can be in collisions so the # of collisions
goes down. That makes the rate of the reaction go down. D) Heat will speed up the particles and make more collisions.
44.Remember the beakers?
At equilibrium the rate of exchange or reaction rate
is what's equal
At equilibrium the amount of product & reactant
remain constant, they do not change.
45. A is the best answer. Reasoning: Out of all the answers only concentration will give you a clue to equilibrium. You
would measure the concentrations several times until the measurements started to remain constant. Then you are at
equilibrium.
46. Remember, equilibrium shifts AWAY from what you ADD; it shifts TOWARD what you TAKE AWAY
a) to increase the amount of SO3 you could: add SO2 or O2 or take away SO3 or heat or you could increase the pressure
on the system.
b) to decrease the amount of SO3 you could take away SO2 or O2 or add SO3 or heat or you could decrease the pressure
on the system.
47. D is the best answer Reasoning: The easiest way to think about this is to remember that the larger the negative
power of 10 the smaller the number. An acid has more H than OH so the unknown that has the least amount of OH in it
has the most H and is probably the acid. Also, you could remember that the negative log is the pOH and that pOH + pH =
14. for a) the pOH = 2 so the pH = 12; a base; for b) the pOH = 4 so the pH = 10, also a base; for c) the pOH = 6 so the pH
= 8, still a base but for d) the pOH = 8 so the pH = 6, showing an acid.
48. D is the best answer Reasoning: Look for the signs that you know are always true! Red Litmus = ACID! Z is the only
one that FOR SURE has red litmus!
49. M1V1 = M2V2 so .2 M HCl (x) = .4 M (10 mL)
x = 20 mL of the acid HCl
50. M1V1 = M2V2 so 25 mL (12M) = 1000mL (x)
x = .3 M
**hint: whenever the sentence says this of that multiply the 2 things connected by 'of'
51. A is the best answer Reasoning: heating moves the solvent particles further away from each other and allows more
room for the solute to mix in-between them. Gases decrease their solubility as they heat up. Miscibility is when both
the solute and solvent are liquids. And you can only increase the degree of saturation if you can add more solute -which is A!
52. A is the best answer Reasoning: On the solubility graph find the KCl line and follow it until it intersects the 800C
mark. When you read over to the Y axis, you'll see that it intersects with the 50 g of KCl for saturation (remember snow
in a test tube?) BUT the trick is that the graph is written for 100 g of the solvent, water. The question asked about 50 g
of the solvent water, so the 50 g of KCl needs to be cut in half as well.
53. C is the best answer (the first C -- "Solute and solvent particles form attractions for one another") Reasoning:
Forming attractions for each other implies that solute & solvent particles are getting close to each other. This may cause
them to slow down and since energy is neither created or destroyed, that extra kinetic energy is given off as heat making
this process ALWAYS exothermic.
54. Gases are always (as far as we are concerned) LESS soluble in a warm solvent than in a cold solvent (think about a 2
Liter soda bottle that you've opened -- out in the warmth of the room on the counter it will go flat fast -- all the carbon
dioxide gas dissolved in it will leave and the soda will lose its fizz. If you want the soda to keep its fizz you must cap it
tightly and put it in the refrigerator, keeping it cool. This is because gas particles move much faster in response to a
smaller amount of heat than a liquid or solid particles. So a small amount of heat causes the gas to move enough to
easily escape the solvent that they are dissolved in.
Answers to the extras:
36) N2 + 3H2 --> 2NH3
40) 36% Ca & 64% Cl
CaCl2
or
4Fe + 3O2 --> 2Fe2O3
67.6% Hg, 10.8% S & 21.6% S
HgSO4