All molecular motion stop at 0 k wich is zero kelvin. At absolute 0 it stops. The temperature of 0 entropy at which all molecular motion stops equals in centigrades to -273.15° C which is the same as 0 in kelvin degrees. Have in mind that t<span>emperature is a measure of the average kinetic energy of the </span>molecules<span> in a material.</span>
A homogeneous mixture is formed when it is dissolved in water
Answer: Statements (A), and (C) are correct.
Explanation:
The statements that are true are as follows.
- Particles in a liquid need to move more slowly in order to freeze.
When a liquid freezes the molecules get attracted towards each other. This attraction of particles occurs slowly. Hence, this statement is true.
- Attractive forces between the particles in a liquid are broken when a liquid boils.
When temperature is raised, the molecules in a liquid gains kinetic energy and start to move quickly in random directions. As a result, liquid state changes to gaseous state. Hence, this statement is true.
If the attractive force between gas molecules have to be increased, they should be moving slower instead because moving faster does not help attracting molecules together.
Hence, the statement particles in gas move fast enough to make more attractive forces when the gas condenses is not true.
8.50 moles is equal to 5.1187×10²⁴ atoms of Ca.
<u>Explanation:</u>
We have to multiply the moles of Ca by the Avogadro's number:
= 6.022×10²³
So the number of atoms:
= 8.5 moles × 6.022×10²³atoms / mol
= 5.1187×10²⁴ atoms
Hence the 8.50 moles is equal to 5.1187×10²⁴ atoms of Ca.
To know this you pretty much do have to kind of memorize a few electronegativities. I don't recall ever getting a table of electronegativities on an exam.
From the structure, you have:
I remember the following electronegativities most because they are fairly patterned:
EN
H
=
2.1
EN
C
=
2.5
EN
N
=
3.0
EN
O
=
3.5
EN
F
=
4.0
EN
Cl
=
3.5
Notice how carbon through fluorine go in increments of
~
0.5
. I believe Pauling made it that way when he determined electronegativities in the '30s.
Δ
EN
C
−
Cl
=
1.0
Δ
EN
C
−
H
=
0.4
Δ
EN
C
−
C
=
0.0
Δ
EN
C
−
O
=
1.0
Δ
EN
O
−
H
=
1.4
So naturally, with the greatest electronegativity difference of
4.0
−
2.5
=
1.5
, the
C
−
F
bond is most polar, i.e. that bond's electron distribution is the most drawn towards the more electronegative compound as compared to the rest.
When the electron distribution is polarized and drawn towards a more electronegative atom, the less electronegative atom has to move inwards because its nucleus was previously favorably attracted to the electrons from the other atom.
That means generally, the greater the electronegativity difference between two atoms is, the shorter you can expect the bond to be, insofar as the electronegative atom is the same size as another comparable electronegative atom.
However, examining actual data, we would see that on average, in conditions without other bond polarizations occuring:
r
C
−
Cl
≈
177 pm
r
C
−
C
≈
154 pm
r
C
−
O
≈
143 pm
r
C
−
F
≈
135 pm
r
C
−
H
≈
109 pm
r
O
−
H
≈
96 pm
So it is not necessarily the least electronegativity difference that gives the longest bond.
Therefore, you cannot simply consider electronegativity. Examining the radii of the atoms, you should notice that chlorine is the biggest atom in the compound.
r
Cl
≈
79 pm
r
C
≈
70 pm
r
H
≈
53 pm
r
O
≈
60 pm
So assuming the answer is truly
C
−
C
, what would have to hold true is that:
The
C
−
F
bond polarization makes the carbon more electropositive (which is true).
The now more electropositive carbon wishes to attract bonding pairs from chlorine closer, thereby shortening the
C
−
Cl
bond, and potentially the
C
−
H
bond (which is probably true).
The shortening of the
C
−
Cl
bond is somehow enough to be shorter than the
C
−
C
bond (this is debatable).
