Experiment 5 (Eng. Vers.).docx

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Basic ChemistryExperiment ModuleExperiment 5 Water Crystals (English Version)

Member of The Group:

Agasta Prio Prasetyo (1306415926) Akwila Eka Meliani (1306413725) Atikah Ridhowati (1306392922) Faraj Sungkar (1306392840) Imas Mega Pratiwi (1306370524) Muhammad Madani (1306405755) Nurania Saubryani (1306392866) R. Muhammad Fathi (1306449290) Syafiq Rayza (1306370606) Vanessa Geraldine (1306370410)

BASIC CHEMICAL PROCESS LABORATORY

DEPARTMENT OF CHEMICAL ENGINEERING FACULTY OF ENGINEERING

UNIVERSITY OF INDONESIA

DEPOK, 2014


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Experiment 5

WATER CRYSTAL

In general, the crystal is a chemical compound which can absorb water on its

surface when it placed in the air. The amount of water that absorbed is relatively

small and depends on the humidity. It can be seen from the surface which is wet.

There are also crystals that contain some water that chemically bound in it. This

crystal is usually an ionic salt. The water that contained in it is called water crystal

and is usually bound to the cation.

Water Crystals that contained in the compound have a certain amount and

relatively easily removed by heating at a temperature above the boiling point of

water. For example, the hydrate of copper (II) chloride can be copper (II) chloride

anhydrate by heating at a temperature of 100C.

Dehydration reaction:

In dehydration, crystals and color will changes. This change also depends on the

heating, whether perfect or not. For example, red colored crystals CoCl2.6H2O, if

heated to CoCl2.6H2O will become violet, but when it is perfectly heated, it will turn

into a perfect blue.

The hydrate compound when placed in the open air will release water. The

amount of water that is released depends on the air humidity. The greater the less

water is released. The process of water release is called efflorescence, for example

CoCl2.6H2O. But there are also some compounds when they placed in the air will

absorb water and melt when placed much longer. Those compounds are called

deliquescence, e.g. NaOH crystal. Not only water in the air, but the crystals can also

absorb water from a solution. Those compounds are called desiccant or drying agent.

So desiccant absorbs water not only in air but also in the solution.

I. BACKGROUND


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Some compounds will produce water when they heated. But, the compound is not

hydrate. The water that produced is from the decomposition not from the removal

process by dehydration. Decomposition that produced water is irreversible process.

Adding water to the decomposed compounds wont make it back into the initial form. The hydrate compounds Wills occur reversible dehydration. The addition of water

into anhydrate CoCl will produce CoCl.2H 2O. If the addition of water is enough, it

will obtain a solution that contain Cu 2+ .

Important properties of polar water molecules when water is used as a solvent.

Water dissolves many ionic compounds easily because the hydration of the ions. A

hydrated ion is an ion with one or more water molecules. The number of molecules in

a solution of water supply ions seems not necessarily, but often times when an

aqueous solution of a soluble salt is evaporated, the salt crystallizes with the right

amount of water molecules, called a water of crystallization. In most cases it turns the

water of crystallization in salts associated with positive ions often in the name of salt

or in writing formulas for names, the name or formula of the hydrated salt was used

for Hydrated salt. For example, a solution of copper sulfate can be expressed by the

formula CuSO 4 in the equation. Though in reality both Cu2+ ions and the ion crystal

water SO 42-. The appearance term because there are some ionic compounds have

unique characteristics, which can bind and attract water molecules in a certain

amount. Own compounds called hydrated compounds (hydrate = water) while the

bound water is called water of hydration or water of crystallization. Water bound in

the structure and can only be removed by heating. After the water off, then

compounds coined a new name, namely the anhydrous compound (an = no).

Determination of the number of water molecules bound to the compound is done

in several ways as follows:

a. If the period of relative molecular compound hydrates are known, the relativemolecular mass of anhydrous compound can also be known. Thus, the amount of

bound water molecules can be determined,

b. ( )


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b. If the water content in the compound known to hydrate, anhydrous compound

levels may also be known. Thus, the mole ratio of anhydrous compound and

moles of water can be determined. As a result, the number of water molecules

bound to the compound can be known as the molecule ratio.

c. If the hydrate compounds with a certain amount of mass in the heat, its mass is

reduced. That is, the water molecules are bound to have come off and the

difference in mass is the mass of the crystal water molecules. Thus, the mass of

anhydrous compound can be known. The ratio, his mole can also be determined

so that the number of water molecules bound to be in the know.

1. To learn dehidration activity and hidration of a solid containing water

crystals.

2. To calculate the empiric formula of water crystals.

Qualitative Observation

1. Ask a assistant 3 kinds of solid materials containing crystalline water.

Observe and write down the name of the substance and their colors and

shapes.

2. Insert those substance into a pyrex test tube each. Label it.

3. Use a wood clamp to hold the test tube, then heat the substance in the tube

on the bunsen burner. Observe and write down the changes happened.4. Then, drop a water into the test tube just a few. Observe and write down

the changes happened.

II. OBJECTIVES

III. PROCEDURES


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5. Write down the reaction equation, all of the heating and watter addition

activity. Explain those equation and the difference between those substance

based on your observation.

Quantitavie Observation

1. Provide 3 pieces of ceramic bowls (evaporator). Weigh and write down the

weight carefully.

2. Insert solids substance containing crystalline water into the third cup, and

write down the weight. Determine the weight of the substance

3. Heat the cup containing sample until they change color just as color samples

of uniform / homogeneous (color sample has changed all of the colors before

warming),stop heating and immidiately weigh carefully weighed.

4. Calculate the weight loss after heating. If weight loss is showing the amount

of water contained in the crystal sample, determine the empiric formula of

crystal water, then compare with the theoritical and empiric formula.

5. Try this experiment for three different sample and show the similiarities and

differences of your observations

CuSO 4.5H 2O

- Eye: Exposure to particulates or solution may cause conjunctivitis, ulceration,

and corneal abnormalities. Causes eye irritation and possible burns.

- Skin: May cause skin sensitization, an allergic reaction, which becomes evident

upon re-exposure to this material. Causes skin irritation and possible burns. May

cause itching eczema.

- Ingestion: Harmful if swallowed. May cause severe gastrointestinal tract

irritation with nausea, vomiting and possible burns. Ingestion of large amounts of

IV. POTENTIAL HAZARDS


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d. If you heat 15.00 g of the hydrate and drive off the water, what is the

weight of the anhydrous salt remaining? Show your work.

4. A hydrate of sodium phosphate, Na 3PO 4, contains 49.7% water by weight.

a. How many grams of water and how many grams of anhydrous Na 3PO 4 arein 1000. grams of this sample?

b. In this same 1000.-gram sample, how many moles of water and how many

moles of anhydrous Na 3PO 4, are present?

c. What is the formula of the hydrate?

5. Give the correct name for the following:

a. Na 2SO410H 2O ___________________________________________

b. Cu(NO3)

2H

2O ___________________________________________

Qualitative Observation

Hydrates Initial Condition Condition after

Heated

Condition after

Adding Water

MgSO 4xH 2OCaCl 2xH 2O

CuSO 4xH 2O

Reaction of Heating Process:

____________________________________________________________________

Reaction of Water Addition Process:

____________________________________________________________________

Quantitative Observation

VII. REPORT SHEETS


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a. MgSO 4xH 2O

Experimental Results:

1. Mass of crucible = _____________________________

2. Mass of crucible& hydrate = _____________________________ 3. Mass of hydrate (1-2) = _____________________________

4. Mass of crucible and hydrate

after heating = _____________________________

5. Mass of water lost (1-4) = _____________________________

Calculation of hydrate formula from the experimental results:

6. Water percentage of hydrate

([5/3] x 100%) = _____________________________

7. Moles of water lost = _____________________________

8. Moles of anhydrite = _____________________________

9. Moles of water per mole of

anhydrite = _____________________________

Hydrate experimental formula = ___________________

Hydrate theoretical formula = ___________________

Percent of Experimental Error = | |

= ___________________

b. CaCl 2xH 2O


1. Mass of crucible = _____________________________

2. Mass of crucible& hydrate = _____________________________

3. Mass of hydrate (1-2) = _____________________________


after heating = _____________________________


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6. Water percentage of hydrate ([5/3] x 100%) = _____________________________



9. Moles of water per mole of

anhydrite = _____________________________

Hydrate experimental formula = ___________________

Hydrate theoretical formula = ___________________

Percent of Experimental Error = | |

= ___________________

c. CuSO 4xH 2O


1. Mass of crucible = _____________________________ 2. Mass of crucible& hydrate = _____________________________

3. Mass of hydrate (1-2) = _____________________________


after heating = _____________________________



6. Water percentage of hydrate

([5/3] x 100%) = _____________________________




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Experiment 5 (Eng. Vers.).docx