WEBVTT
1
00:00:00.380 --> 00:00:02.940 A:middle L:90%
to compare quantities, we need to know several different
2
00:00:02.940 --> 00:00:08.150 A:middle L:90%
relationships between moles, molecules, atoms and ions.
3
00:00:08.939 --> 00:00:12.849 A:middle L:90%
So if you are given a certain quantity of moles
4
00:00:13.740 --> 00:00:19.280 A:middle L:90%
, we know that every one mole of a substance
5
00:00:19.280 --> 00:00:29.510 A:middle L:90%
contained 6.2 times 10 to the 23rd things, which
6
00:00:29.510 --> 00:00:35.740 A:middle L:90%
is sometimes called an entity. So in this case
7
00:00:35.740 --> 00:00:39.929 A:middle L:90%
, if we have 0.4 moles of 03 4.4 moles
8
00:00:39.929 --> 00:00:43.909 A:middle L:90%
of 02 they both have the same number of particles
9
00:00:43.909 --> 00:00:55.130 A:middle L:90%
, so these quantities are equal. If instead of
10
00:00:55.130 --> 00:00:57.799 A:middle L:90%
asking about number of particles or entities, we asked
11
00:00:57.799 --> 00:01:00.810 A:middle L:90%
about Gramm's. We need to use the molar Mass
12
00:01:00.810 --> 00:01:07.480 A:middle L:90%
to compare. So if I have 0.4 moles of
13
00:01:07.489 --> 00:01:11.409 A:middle L:90%
03 to change that two grams, I use the
14
00:01:11.409 --> 00:01:17.549 A:middle L:90%
molar Mass or looking on the periodic table, I
15
00:01:17.549 --> 00:01:19.640 A:middle L:90%
add up. We're multiplying this case three times the
16
00:01:19.640 --> 00:01:27.780 A:middle L:90%
molar mass of oxygen, so 0.4, divided by
17
00:01:27.790 --> 00:01:38.689 A:middle L:90%
three times 15.99999 equals 19.2 grams. Similarly, if
18
00:01:38.689 --> 00:01:47.659 A:middle L:90%
we look at our mules of oxygen Adams one mole
19
00:01:48.640 --> 00:01:56.349 A:middle L:90%
has a mass of 15.999 grams, 4.4 divided by
20
00:01:56.349 --> 00:02:01.950 A:middle L:90%
15.999 is 6.4 grabs. So using the molar mass
21
00:02:02.939 --> 00:02:13.490 A:middle L:90%
, we can see that 0.4 moles 03 has more
22
00:02:13.490 --> 00:02:25.110 A:middle L:90%
grams in 0.4 moles of Oh, you can see
23
00:02:25.110 --> 00:02:32.349 A:middle L:90%
a similar thing with different compounds four grams of end
24
00:02:32.360 --> 00:02:37.939 A:middle L:90%
to 04 changing two moles again, I use the
25
00:02:37.939 --> 00:02:43.849 A:middle L:90%
molar mass, which is two times the molar mass
26
00:02:43.849 --> 00:02:53.409 A:middle L:90%
of nitrogen, plus four times the molar mass of
27
00:02:53.419 --> 00:03:05.840 A:middle L:90%
oxygen or four. Divided by this number is 0.0
28
00:03:05.849 --> 00:03:16.909 A:middle L:90%
for three Knowles. 3.3 grams of eso to divided
29
00:03:16.909 --> 00:03:22.509 A:middle L:90%
by its smaller mass, which is the molar mass
30
00:03:22.520 --> 00:03:44.669 A:middle L:90%
sulfur plus two times the molar mass oxygen equals 0.52
31
00:03:44.669 --> 00:03:53.949 A:middle L:90%
moles. So we see that 3.3 grams eso to
32
00:03:54.539 --> 00:04:00.650 A:middle L:90%
has more moles than four grams of end to four
33
00:04:12.240 --> 00:04:15.250 A:middle L:90%
given mole to convert to grams a similar process using
34
00:04:15.250 --> 00:04:18.399 A:middle L:90%
molar Mass. Except in this case, we multiply
35
00:04:18.399 --> 00:04:23.819 A:middle L:90%
by the molar Mass. So 0.6 malls of C
36
00:04:23.819 --> 00:04:30.670 A:middle L:90%
two H four times the molar mass, which is
37
00:04:30.850 --> 00:04:35.209 A:middle L:90%
two times the molar mass of kurban, plus four
38
00:04:35.209 --> 00:04:45.120 A:middle L:90%
times the molar mass of hydrogen tells us that this
39
00:04:45.120 --> 00:04:58.860 A:middle L:90%
is equivalent 16.8 grams 0.6 moles of F two multiplied
40
00:04:58.860 --> 00:05:09.519 A:middle L:90%
by its smaller mass just to times 18 0.99 eight
41
00:05:12.240 --> 00:05:26.660 A:middle L:90%
is equivalent to 22.8 grams. So 0.6 moles of
42
00:05:26.660 --> 00:05:32.829 A:middle L:90%
F two is more grams than 0.6 moles of C
43
00:05:32.829 --> 00:05:42.660 A:middle L:90%
two h four. If you're given an Ionic compound
44
00:05:42.660 --> 00:05:45.279 A:middle L:90%
and asked to look at number of ions first,
45
00:05:45.279 --> 00:05:47.649 A:middle L:90%
we have to figure out which ions make these compounds
46
00:05:48.139 --> 00:05:50.519 A:middle L:90%
. It's a sodium chlorate is made up of this
47
00:05:50.519 --> 00:05:56.259 A:middle L:90%
sodium ion, an A plus in the chlorate and
48
00:05:56.259 --> 00:06:00.899 A:middle L:90%
I in Cielo three minus. So there's one eye
49
00:06:00.899 --> 00:06:02.850 A:middle L:90%
on a sodium in one eye on a quarry quarry
50
00:06:02.860 --> 00:06:10.410 A:middle L:90%
to make so didn't glory. So if I have
51
00:06:10.420 --> 00:06:17.769 A:middle L:90%
to 0.3 moles of N a. C l 03
52
00:06:19.079 --> 00:06:25.470 A:middle L:90%
this is equivalent to multiplying it by 6.2 times 10
53
00:06:25.810 --> 00:06:34.389 A:middle L:90%
to the 23rd Formula. Unit Formula Unit is just
54
00:06:34.389 --> 00:06:43.500 A:middle L:90%
one ionic compound unit. Her mole and I know
55
00:06:43.500 --> 00:06:46.850 A:middle L:90%
that there are two ions for every formula unit,
56
00:06:56.040 --> 00:07:00.069 A:middle L:90%
so multiplying 2.3 times 6.2 times 10 to the 23rd
57
00:07:00.079 --> 00:07:08.839 A:middle L:90%
times two tells us there 2.77 times 10 to the
58
00:07:08.839 --> 00:07:16.370 A:middle L:90%
24th ions. Similarly, with magnesium chloride magnesium is
59
00:07:16.370 --> 00:07:19.509 A:middle L:90%
made up of M G two plus and C L
60
00:07:19.509 --> 00:07:25.750 A:middle L:90%
minus, So the formula is mg seal, too
61
00:07:26.269 --> 00:07:29.389 A:middle L:90%
. There are three ions, one magnesium and two
62
00:07:29.389 --> 00:07:36.750 A:middle L:90%
Korans. So if I have 2.2 moles of magnesium
63
00:07:36.750 --> 00:07:56.529 A:middle L:90%
chloride, changing that to formula units and then multiplying
64
00:07:56.529 --> 00:08:07.649 A:middle L:90%
by three ions for every formula unit, this equals
65
00:08:07.339 --> 00:08:16.250 A:middle L:90%
3.97 times 10 to the 24 I on. So
66
00:08:16.250 --> 00:08:24.850 A:middle L:90%
there are more total ions and 2.2 moles magnesium chloride
67
00:08:39.539 --> 00:08:41.610 A:middle L:90%
, every look at number of molecules. In a
68
00:08:41.610 --> 00:08:46.379 A:middle L:90%
certain quantity, you have to change from grams to
69
00:08:46.379 --> 00:08:50.750 A:middle L:90%
moles to molecules, So one gram of H 20
70
00:08:54.039 --> 00:08:58.350 A:middle L:90%
It's changed two moles by dividing by the molar mass
71
00:08:58.840 --> 00:09:01.549 A:middle L:90%
, which is two times molar mass of hydrogen,
72
00:09:03.139 --> 00:09:11.440 A:middle L:90%
plus the molar mass of oxygen, then changing two
73
00:09:11.440 --> 00:09:15.330 A:middle L:90%
molecules by multiplying by, Ah, for God,
74
00:09:15.330 --> 00:09:41.299 A:middle L:90%
rose number. Similarly, the same steps for H
75
00:09:41.299 --> 00:09:46.100 A:middle L:90%
202 or hydrogen peroxide. The only difference is the
76
00:09:46.100 --> 00:09:52.019 A:middle L:90%
molar mass. One more is equal to two times
77
00:09:52.019 --> 00:09:56.250 A:middle L:90%
the molar mass of hydrogen, plus two times the
78
00:09:56.250 --> 00:10:07.730 A:middle L:90%
molar mass of oxygen and then multiplying again by Abu
79
00:10:07.730 --> 00:10:26.179 A:middle L:90%
God. Rose number or 1.77 times 10 to the
80
00:10:26.179 --> 00:10:31.600 A:middle L:90%
22nd molecules, so there are more molecules in one
81
00:10:31.600 --> 00:10:39.620 A:middle L:90%
gram of water. Then there are in one gram
82
00:10:39.620 --> 00:10:48.879 A:middle L:90%
of hydrogen peroxide. And finally, if we're given
83
00:10:48.879 --> 00:10:52.179 A:middle L:90%
an atomic symbol, you to 35. This means
84
00:10:52.360 --> 00:10:58.850 A:middle L:90%
that the atomic weight is 235 atomic mass units,
85
00:10:58.539 --> 00:11:01.649 A:middle L:90%
as opposed to a mole of uranium to 38.
86
00:11:05.340 --> 00:11:07.850 A:middle L:90%
And so this has a slightly larger mass than this
87
00:11:09.340 --> 00:11:16.009 A:middle L:90%
. So subsequently you to 38 we'll have more mass
88
00:11:16.009 --> 00:11:20.299 A:middle L:90%
than you 2 35