What is the difference between the molecular formula and empirical formula?

The molecular formula indicates the types and exact number of each atom in a compound, while the empirical formula shows the simplest ratio of the elements.

How do you calculate the empirical formula from percentage composition by mass?

First, list the elements with their respective percentage compositions. Then divide each by its atomic mass and find the simplest ratio.

How is the molecular formula derived from the empirical formula?

The molecular formula is the empirical formula multiplied by a whole number (n), determined by dividing the molecular mass by the empirical mass.

Empirical Formulae From Percentage Composition | Chemical Calculations | Chemistry | FuseSchool

00:04:33

https://www.youtube.com/watch?v=5xVTw6LFG2E

Zusammenfassung

TLDRThis video lesson covers the difference between empirical and molecular formulas and teaches how to derive them. The molecular formula of a compound indicates the types of atoms present and their exact count, while the empirical formula provides the simplest ratio of these atoms. An example with a compound of nitrogen and hydrogen is used, where the molecular formula is N2H4 and the empirical formula is NH2. The process involves calculating from percentage composition by mass: dividing the percentages by atomic masses, finding the simplest ratio, and using the empirical formula to find the molecular formula by factoring in the molecular mass.

Mitbringsel

🔍 Empirical formula shows simplest ratio of atoms.
🧪 Molecular formula gives exact number of atoms.
📊 Use percentage composition to find empirical formula.
🔢 Ratio simplification is key in empirical formula.
🔀 Empirical to molecular formula conversion involves molecular mass.
📉 Nitrogen and hydrogen example illustrates concept.
📏 Empirical mass helps find the molecular formula.
💡 Understand atomic composition through formulas.
🔬 Chemistry formulas reveal elemental structure.
🧮 Calculate elements' ratios accurately.

Zeitleiste

00:00:00 - 00:04:33
This video covers the differences between empirical and molecular formulas and guides on how to derive them from percentage composition. Using hydrazine (N2H4) as an example, it explains that the molecular formula indicates both the types and the exact number of atoms present, while the empirical formula shows the types and the simplest ratio of those atoms. For empirical formulas derived from mass percentages, the method involves calculating the ratio of atoms by dividing percentage over atomic mass and simplifying results. In contrast, deriving the molecular formula involves multiplying the empirical formula by a whole number determined by dividing molecular mass by empirical mass, exemplified through computations.

Mind Map

Häufig gestellte Fragen

What is the difference between the molecular formula and empirical formula?
The molecular formula indicates the types and exact number of each atom in a compound, while the empirical formula shows the simplest ratio of the elements.
How do you calculate the empirical formula from percentage composition by mass?
First, list the elements with their respective percentage compositions. Then divide each by its atomic mass and find the simplest ratio.
How is the molecular formula derived from the empirical formula?
The molecular formula is the empirical formula multiplied by a whole number (n), determined by dividing the molecular mass by the empirical mass.

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Untertitel

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00:00:10
[Music]
00:00:14
in this video you're going to learn the
00:00:16
difference between empirical formula and
00:00:18
molecular formula how to find the
00:00:21
empirical formula from percentage
00:00:23
composition by mass and how to find
00:00:26
molecular formula from the empirical
00:00:29
formula consider the compound hydren its
00:00:33
molecular formula is
00:00:35
n2h4 but its empirical formula is
00:00:39
nh2 the molecular formula of a compound
00:00:43
tells us two things one the types of
00:00:46
atom in the molecule in this case
00:00:48
nitrogen and hydrogen and two how many
00:00:52
types of each atom in this case there
00:00:54
are two nitrogen atoms and four hydrogen
00:00:58
atoms the EMP empirical formula of a
00:01:01
compound also tells us two things one
00:01:04
the types of atoms in the molecule in
00:01:07
this case nitrogen and hydrogen and two
00:01:10
the simplest ratio of each type of atom
00:01:13
the ratio of nitrogen to hydrogen in
00:01:16
hydrogene is 2: 4 making the simplest
00:01:20
ratio
00:01:21
1:2 the best way to find the empirical
00:01:24
formula from percentage composition by
00:01:27
mass is to go over a question upon
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analysis the percentage composition by
00:01:33
mass of a compound was found to be
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87.5% nitrogen and 12.5% hydrogen now
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calculate the empirical formula firstly
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we have a column for each element n for
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nitrogen and H for hydrogen then under
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each element we put the percentage
00:01:53
composition by mass so that's
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87.5% for nitrogen and 12 .5% for
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hydrogen we then divide these
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percentages by the relative atomic mass
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of each element so that's 14 for
00:02:09
nitrogen and one for hydrogen doing this
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calculation gives us
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6.25 for nitrogen and 12.5 for hydrogen
00:02:20
we then divide these numbers by the
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smallest of the two which is
00:02:26
6.25 and this gives us the ratio of 1 to
00:02:30
2 1 and two is the smallest possible
00:02:34
ratio so the empirical formula is n H2
00:02:39
but how do we find the molecular formula
00:02:41
the molecular mass for this compound is
00:02:45
32 the molecular formula is the
00:02:47
empirical formula time n where n is the
00:02:51
number by which we have to multiply the
00:02:54
empirical formula in order to get the
00:02:56
molecular formula I have coined the
00:02:59
phrase empirical Mass to describe the
00:03:01
mass of the empirical formula so in this
00:03:04
case we have nitrogen which is 14 plus
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hydrogen which is 2 giving us 16 now
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just as the molecular formula is the
00:03:15
empirical formula time n the molecular
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mass is the empirical mass time n so
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molecular mass of 32 is n * the
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empirical Mass 16
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therefore n is 32 / 16 or 2 so now
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molecular formula is the empirical
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formula time n so that's nh2 * n or nh2
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* 2 which gives us N2
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H4 so to recap the mular formula tells
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us the types of atoms in a molecule and
00:03:58
their exact number and the empirical
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formula tells us the types of atoms in
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the molecule and their simplest
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ratio