Pretest 3.5 STE Answers
1.
Name the following or give the formula when the name is already given:
a) NaHCO3
b) CCl4
c) potassium phosphate
d) dihydrogen monoxide
a) sodium hydrogen carbonate
b) carbon tetrachloride
c) K3PO4
d) H2O
2.
Use algebra to find the abundance of 302X
X has an atomic weight of 303.05 amu
Mass number of
isotope
Percent composition
299
35.2%
302
????
311
?????
solve(0.352*(299) + x*(302)+ (1-x-0.352)*(311) = 303.05, x);
note that 1 = 100%
x = .4140000000
41.4% for isotope 302
1
3.
CaCl2 does not bond the way CH2Cl2 does. Show the difference.
Calcium chloride is ionic (metal + nonmetal) so:
Then there’s a repeatng pattern within a crystal:
2
4.
Given: 2Al +3Cl2→2 AlCl3
When 80 grams of aluminum is reacted with excess chlorine gas, how many individual
ions of Al+3 are produced? Chloride ions?
80 g Al (mol/27 g) = 2.96 moles Al
There is a 1:1 ratio(2:2) between Al and AlCl3 , therefore there are 2.96 moles AlCl3 .
2.96 moles AlCl3 X 6.02 X 1023 ions of Al+3/mole AlCl3= 1.78×1025 ions
For every mole of Al+3 there are 3 chloride ions, so = 3 X 1.78×1025
5.
=
5.34 X 1025
a)
What is the work performed by a horse pulling a carriage with an 8 N
force over a 2 km distance?
W = F*d
= 8 N *2000m = 16 000 J
b) What two assumptions regarding applied force and friction did you make in solving the
above problem?
We’re assuming that the force of 8N is in the same direction as the motion of the carriage. And
we are also assuming there’s no friction.
6.
After the prom at the Vaudreuil Castle, which is not really a castle, Joe refuses to drive
fast. He doesn’t want to crash because he enjoys kissing his girl friend and solving physics
3
problems. To convince his friends to be cautious, he urges them to calculate the ratio of kinetic
energy of his 2000 kg vehicle moving at 120 km/h versus his vehicle moving at 80 km/h.
a) Calculate that ratio.
𝑘𝑚 2
𝑚 2
(120
)
(1000
)
(120 )2
𝐸1
0.5 𝑚𝑣12
𝑣12
3600𝑠
ℎ
=
= 2=
2 ∗
2 = (80 )2
𝑚
𝐸2 0.5 𝑚𝑣22
𝑣2
𝑘𝑚
(1000
)
(80
)
3600𝑠
ℎ
9
= 2.25 𝑜𝑟
4
b) If his car was moving initially at 120 km/h ( 33.3 m/s) on a ramp 12 m above the road below
it, how fast will he go if he just lets his car go down the ramp without applying the break?
Assume no friction.
Total energy = mgh1 + 0.5mv12 = mgh2 + 0.5mv22
Total energy = gh1 + 0.5 v12 = gh2 + 0.5 v22
Total energy = 9.8 m/s2 (12 m) + 0.5 (33.3 m/s) 2 = 9.8 m/s2 (0) + 0.5 v22
V2 = 36. 3 m/s = 131 km/h
4
Genetics
7.
a) Show a Punnett square for Rr X rr, where R = round and r is the allelic gene
for wrinkled peas.
r
r
R
Rr
Rr
r
rr
rr
b) What is the genotypic ratio for this crosss?
1: 1 of Rr to rr
c) Phenotypic ratio?
1:1 of round to wrinkled
d) how many chromosomes carry the genes Rr?
2
e) How many R genes are found in 5 pea egg cells?
Between 0 and 5. The eggs can carry only 1 gene for roundness.
5
8.
List two ways by which dandelions can clone themselves-----or explain the way
potatoes can clone themselves.
Female dandelions can strangely produce seeds without males, so they clone
themselves and they can also clone themselves with their roots.
Potatoes gorw “eyes” which then become stems and roots and grow into a clone of
the ooriginal plant, which eventually produces more potatoes.
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