(Solved by Humans)-What is the percent composition of water of Fe F 2 - 4H 2 O?

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What is the percent composition of water of? Fe F_{2? -} 4H₂O?

43.4%

19.4%

12.2%

16.01%

What is the correct name for? CaSO_{4?? x???} 2H₂O?

none of these

calcium sulfate dihydrate

calcium sulfide dihydrate

calcium sulfur hydrate

What is the percent of water in? Na₂CO_{3??? x} 10H₂O

85.5% H2O

62.9% H20

53.9% H2O

74.6% H20

Chemistry: SCI 1100
Hydrates
Objectives
Student will compare and contrast hydrate and anhydrous
compounds.
Students will name hydrates.
Student will determine the correct formula for hydrate.


Vocabulary
anhydrous
compound
hydrate



A compound with NO water with in
the molecular structure.
A compound with one plus water
molecules bound to the formula unit



A hydrate is a compound with water molecules within the
formula unit but it is also an ionic compound. The water is
part of the crystalline lattice structure. A compound can a
have a form which is hydrated and a form which is
anhydrous. The anhydrous form lacks the water within its
structure.The figure below shows a watch?glass with
Copper (II) Sulfate. Both colors are Copper (II) Sulfate, the
blue is the hydrate and white is anhydrous.


by Benjah?bmm27?Via Wikipedia ?Public Domain



Naming Hydrates
There are a couple of things to take into consideration
when naming hydrates






Remember the rules of naming ionic compounds (you
will need your polyatomic ions chart)
The ionic compound is named first
The number of waters will be represented by a prefix
(See the table below) followed by the word hydrate.



Example 1:



Name the ionic compound first Iron (II) Fluoride



Next name the hydrate, there are 4 so tetrahydrate
Iron (II) Fluoride tetrahydrate.




Example 2:





Name the ionic compound first Cobalt (II) chloride
Then name the hydrate, there are six, so
hexahydrate.
Cobalt (II) chloride hexahydrate




Percent Composition of Water in a Hydrate



Finding the percent composition of water is a little different
from the way you did in a few lessons back. To find

percent composition of water, we are going to use water
as a unit. Instead of breaking water down into individual
hydrogen and oxygen, you are going to keep it as one
unit. This will be the formula you will use:





Example 3.
Find the percent composition of water of Calcium Chloride
dihydrate.





Find the molar mass of the element in the ionic
compound
o

Ca 1 x 40.1 = 40.1 grams



Cl 2 x 35.5 = 71.0 grams



Find the molar mass of the water AS A WHOLE



There are 2 waters (see the coefficient)



the molar mass of water is 18 grams



H O 2 x 18g= 36.0 grams
2



Now total up all of the masses



o

Ca 40.1

o

Cl 71.0

o

H O 36.0

o

147.1 grams mass of total compound.



2





\frac{36.0\:grams\:}
{147.1\:grams\:}\times100\%\:=\:24.5\%





The percent of water is 24.5%



Solution details: