Some solar-heated homes use large beds of rocks to store heat. (a) How much heat is absorbed by 100.0 kg of rocks if their temperature increases by 12°C? (Assume that c = 0.82 J / g ⋅ °C .) (b) Assume that the rock pile has total surface area 2 m 2 . At maximum intensity near the earth's surface, solar power is about 170 watts/m 2 . ( 1 watt = 1 J / s . ) How many minutes will it take for solar power to produce the 12°C increase in part (a)?
Some solar-heated homes use large beds of rocks to store heat. (a) How much heat is absorbed by 100.0 kg of rocks if their temperature increases by 12°C? (Assume that c = 0.82 J / g ⋅ °C .) (b) Assume that the rock pile has total surface area 2 m 2 . At maximum intensity near the earth's surface, solar power is about 170 watts/m 2 . ( 1 watt = 1 J / s . ) How many minutes will it take for solar power to produce the 12°C increase in part (a)?
Solution Summary: The author explains how the time taken for solar power to produce a temperature increase is calculated.
Some solar-heated homes use large beds of rocks to store heat.
(a) How much heat is absorbed by 100.0 kg of rocks if their temperature increases by 12°C? (Assume that
c
=
0.82
J
/
g
⋅
°C
.)
(b) Assume that the rock pile has total surface area 2 m2. At maximum intensity near the earth's surface, solar power is about 170 watts/m2.
(
1
watt
=
1
J
/
s
.
)
How many minutes will it take for solar power to produce the 12°C increase in part (a)?
Suppose sodium sulfate has been gradually added to 100 mL of a solution containing calcium ions and strontium ions, both at 0.15 mol/L. Indicate the alternative that presents the percentage of strontium ions that will have precipitated when the calcium sulfate begins to precipitate.
Data: Kps of calcium sulfate: 2.4x10 ⁻ ⁵; Kps of strontium sulfate: 3.2x10 ⁻ ⁷
A) 20,2 %
B) 36,6 %
C) 62,9 %
D) 87,5 %
E) 98.7%
14:43 A
Candidate Identification
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14. The following diagrams represent
hypothetical membrane structures with
their components numbered from 1 to 6.
Based on the figures and your knowledge
of biological membranes, select the
correct alternative.
|
3
5
||
人
2
500000
6
A) Structures 1, 3, 5, 2 and 4 are present
in a constantly fluid arrangement that
allows the selectivity of the movement
○ of molecules. Structure 4, present
integrally or peripherally, is responsible
for this selection, while the quantity of 6
regulates the fluidity.
B) The membranes isolate the cell from
the environment, but allow the passage
of water-soluble molecules thanks to
the presence of 2 and 3. The membrane
in scheme is more fluid than that in
55
12. Mark the correct statement about
reactions a and b :
a.
Br
+ -OH
Br
b.
+ Br
H₂O
+
Br
-OH
+
H₂O
A) The reactions are elimination
reactions, with reaction "a" being of type
E2 and reaction "b" being of type E1.
B) Reaction "a" is an E2 type elimination
occurring in one step and reaction "b" is
an SN1 type substitution.
C) Both reactions can result in the
formation of carbocation, but in reaction
"b" the most stable carbocation will be
formed.
D) Both reactions occur at the same rate
○ and have the same number of reaction
steps.
E) Reaction "b" is an E2 type elimination
occurring in two steps and reaction "a" is
an SN2 type substitution.
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