final lab#1

Chemistry 12

Lab Book

Hirdapaul Dhillon

SCH4U

SCH4U

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Lab # 1:

Determining the Chemical Formula of a Copper Chloride Hydrate Pg: 3 – 17

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Determining the Chemical Formula of a

Copper Chloride Hydrate Compound

SCH4U - Lab 1 Review of Chem 11

Purpose:

Calculate the empirical formula of the copper chloride hydrate compound. Include moles of the hydrate.

Introduction:

This lab encompassed many concepts studied in the grade 11 chemistry

course. These topics included molar stoichiometry, writing and balancing chemical equations, and the methodology required to derive an empirical formula. Furthermore, the technique and ability to observe and analyze both physical and chemical changes and then vividly, yet concisely and effectively record observations as qualitative and quantitative results was practiced. In addition, the percentage error was applied to verify the final results for this lab experiment. Lastly, a new laboratory technique was introduced, learnt, and then applied; ‘heating to constant mass’. The following few paragraphs are comprised of explanations for the array of topics involved in this lab experiment: -

The concept of the mole is absolutely essential to understanding many aspects of chemistry. The mole is the fundamental base unit in the SI system for the amount of pure substance of a system, which contains the same number of elementary entities as there are atoms in 12 grams of the isotope carbon 12. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or other specified groups of such particles. The number of particles making up one mole of the substance is 6.0225 × 1023, or Avogadro's number. The number of moles in a substance shares a relationship with the mass and molar mass of the substance. Their relationship can be revealed through the structure of their equations. (See below)

n = number of moles Mr = Molar Mass m = mass of substance

n = Mr = m = n · Mr

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This lab experiment involved two types of data: quantitative and qualitative. There is a definite distinction between these two types of data. Qualitative data is data that is personal judgment, which is unrelated to numerical information, while qualitative data is data presented in numbers; it is measurable.

Quantitative data includes the physical and chemical changes that occur during a chemical reaction. During a chemical reaction many changes occur; in order to distinguish between the two types of changes a few key points should be kept in mind. Physical changes occur when no new substance is made, and the change is usually easy to reverse. Physical change deals with energy and states of matter, thus examples of this type of change could be of melting, freezing, vaporization, condensation, sublimation, or any other change in state of matter. On the other hand, chemical changes occur when a new substance is made, and often the change is difficult to reverse. A chemical change is also usually accompanied by a colour change, a different odour, gas production, an emission of light, sound, or heat, more specifically, a popping sound.

This leads into stoichiometry, which is the calculation of quantitative

relationships of the reactants and products in a balanced chemical reaction. Chemical reactions are represented by balanced chemical equations. Proper interpretation of an equation provides a great deal of information about the reaction it represents and about the substances involved in the reaction. For example, the coefficients in a balanced chemical equation indicate the number of moles of each substance in the reaction. Therefore the ratio of moles of one substance to moles of any other substance in the reaction can be easily determined.

A very crucial skill was required in order to arrive at a conclusion in this lab, and it was how to balance chemical equations. A chemical equation is balanced when the number of atoms of each type on each side of the equation is the same. This concept follows the law of conservation of mass; matter (atoms) cannot be created nor destroyed during a chemical reaction. In addition, atoms cannot be randomly added on to each side, only the molecules of the reactants can be worked with. An example of an unbalanced chemical equation for the reaction between hydrogen and oxygen gas would appear as written below:

H2 + O2 H2O

After balancing the above chemical equation it becomes:

2H2 + O2 2H2O

Before the equation was balanced the equation told us that two H atoms reacted with two O atoms to form one water molecule. But one water molecule only contains one oxygen atom, thus according to the unbalanced equation one

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oxygen atom is missing or has been destroyed; this does not follow the law of conservation of mass. To write the chemical equation correctly, the number of atoms on the left side of the chemical equation has to be precisely balanced with the atoms on the right side of the equation. That is why a coefficient of 2 was placed before the reactant hydrogen molecule. This coefficient causes the equation to be balanced and follow the law of conservation of mass, as know 2 hydrogen molecules bond with one oxygen molecule to form 2 water molecules.

In this lab we were to solve for the formula of the copper chloride hydrate; meaning for this specific lab experiment it did not matter whether we solved for the empirical or chemical formula for the compound as both were the same. Nevertheless, there does exist a clear distinction between the two types of formulas, which must be addressed. Chemcial formulas express the exact composition of a molecule or substance using the chemical abbreviations of the chemical elements. On the other hand, empirical formulas use the simplest (lowest) whole-number ratio of the elements that are present. For example, the chemical formula of benzene is C6H6, but the empirical formula is simply CH.

Theoretical yield is the maximum number of grams of product expected from the reaction when the limiting reagent is completely consumed. The theoretical yield is the maximum amount of product that can be produced from the quantities of reactants used. However, the amount of product predicted by the theoretical yield is infrequently actually obtained due to side reactions, losses, or other complications. The actual yield of product is often given as a percentage of the theoretical yield. This is called the percent yield, which describes the efficiency of the reaction and is calculated from the expression:

% yield= (actual yield/theoretical yield) x 100.

Lastly, it is of great value to learn the technique of heating to constant mass. Heat to constant mass means to keep heating and reweighing the reaction until its mass no longer changes, i.e. "constant mass".

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Materials:

Apparatus Quantity

1. Copper (?) Chloride Hydrate 1.00 g

2. Aluminum wire (Al) 0.25 g

3. 6M Hydrogen Chloride (HCL) Few drops approx. < 15mL

4. Distilled Water (H2O) 16 mL

5. Ethanol (C2O5OH) Few drops approx. < 10mL

6. Retort stand 1

7. Pipette 1

8. Electronic Scale 1

9. Crucible (no lid) 1

10. Clay triangle 1

11. Graduated cylinder 1

12. 50 mL Beaker 13. Glass funnel 1

14. Bunsen Burner 1

15. Filter paper 1

16. Iron ring 1

17. Apron 1

18. Protective lab goggles 1

19. Gloves 1

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Method:

1. Firstly, materials were gathered. (See materials list) 2. Secondly, the electronic balance was used to accurately mass, in grams, a

pure crucible (devoid of impurities and without the lid), after which the data was recorded in a quantitative table. Sig Figs were kept to two decimal points, therefore this remained constant when mass of substances and other lab equipment was determined.

3. Thirdly, 1.00 gram of Copper Chloride hydrate was massed in a crucible on

an electronic balance. The data was recorded in a quantitative table. 4. Next, the crucible containing copper chloride hydrate was placed on a clay

triangle, supported by an iron ring attached to the retort stand, which allowed the copper chloride hydrate to sit securely over the flame of the Bunsen burner.

5. It was ensured that the intensity of the flame was kept at a steady and

moderate level to ensure that the evaporation of the water did not take an unreasonably long time, nor was it excessively heated to prevent loss of mass of the copper chloride.

6. The copper chloride hydrate was heated to a constant mass. It had become

visibly apparent that the copper chloride hydrate had evaporated as the color of the crystals changed from a turquoise to a brown color. This had qualitatively signified that the water had evaporated.

7. The crucible and its contents were allowed to cool for a few minutes before

they were massed. The data was recorded in a quantitative table. 8. The mass of the evaporated water was determined by subtracting the mass

of the anhydrous copper chloride from the initial copper chloride hydrate. The data was recorded in a quantitative table.

9. Next, the anhydrous copper chloride was flushed thoroughly out of the

crucible and into a 50mL beaker, using 16mL of distilled water. 10. The contents inside the 50mL beaker were than swirled around; ensuring

that all crystals of copper chloride were dissolved.

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11. A 0.25g of aluminum strip was loosely coiled and placed into the solution. 12. A reaction occurred between the aluminum from the aluminum strip and the

copper in the copper chloride solution. Observations of the reaction were recorded in a qualitative table.

13. After the reaction the copper had deposited onto the aluminum strip. In

order to completely remove the copper from the strip an adequate amount of 6M HCL was applied using a dropper.

14. The once circular piece of filter paper and glass disk were massed separately.

The individual data was recorded in a quantitative table. 15. A gravity filter was fashioned to separate all the contents in the beaker from

the copper. One circular piece of filter paper was folded into a funnel shape and then placed in a glass funnel, which was placed over a beaker.

16. Once all the copper was removed from the strip and placed into the beaker,

all the contents were poured into the glass funnel, and thus the unknown amount of copper remained on the filter paper, while the other contents strained through.

17. A few drops of ethanol were applied to the contents in the glass funnel as it

allowed the contents to dry quicker. 18. Once all the contents in the beaker had strained through the filter paper and

only the copper remained atop the filter paper, then the filter paper with the copper was relocated onto a glass disk.

19. The copper, the filter paper, and the glass disk were placed in an incubator

and allowed to dry over a period of several hours to a little over twenty-four hours.

20. Finally, the copper, filter paper, and glass disk were massed as a whole unit.

The data was recorded in a quantitative table. The mass of the unknown amount of copper was determined by subtracting the mass of the filter paper and glass disk from the mass of the whole unit.

21. All calculations and recorded quantitative data were kept in grams and to

two significant figures.

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Safety- Hazardous Material Assessment

Chemical

Compounds

Safe Handling

Responsive action to related

medical emergency

Storage & Disposal

Copper (1) and (II) chloride are both included in the chart as the correct form of copper is an unknown. CuCl2 ∙ xH2o (However, for the Safety Chart copper (I) & (II) chloride have the same information)

Harmful if swallowed or inhaled – Use common sense and experiment in well-ventilated area.

Inhalation: If inhaled, remove to fresh air. Depending on severity artificial respiration, loosening of tight clothing and administration of oxygen could be implemented. Get medical attention immediately. Ingestion: Get medical attention immediately. Do not induce vomiting unless medical professional has authorized action.

Storage: Keep container tightly closed and in a cool, well-ventilated area. Waste Disposal: Waste must be disposed of in accordance with federal, state and local environmental control regulations.

Severe eye irritant- Safety goggles must be worn at all times throughout the lab procedure. Skin irritant- Experiment cautiously to prevent contact with the skin or hair; beneficial to wear clothes covering most of the skin, especially long shirts, pants, and gloves.

Eye Contact: Remove glasses or any contact lenses, and immediately begin flushing eyes with a lot of water (cold water may be used) for at least 15 min. Get medical attention immediately. Skin Contact: Skin must be immediately flushed with plenty of water for at least 15 min. All contaminated outerwear should be removed. Depending on the severity of contact disinfectant soap and an anti-bacterial cream may be applied, or medical attention may be required.

Hazards in presence of various substances: Contact with metals can form flammable hydrogen gas. Violent reaction can erupt upon contact with potassium, sodium, hydrazine, nitromethane, acetylene, and hypobromite. Contact with acids or acid fumes can cause toxic hydrogen chloride fumes. Slightly explosive in presence of heat.

Use common sense and extra caution to ensure that the copper chloride does not react with the listed elements. In the case of a small fire, remove all other surrounding flammable materials and evacuate vicinity and douse the flame using a fire extinguisher. In the case of an unmanageable fire, evacuate vicinity immediately and alert the fire dpt. If toxic fumes are generated then evacuate vicinity and alert the appropriate authorities. The vapors generated from a large spill of copper chloride can be controlled by using a water spray.

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Hydrochloric Acid (HCl)

Refer to copper chloride





Hazards in presence of various substances: Highly reactive with metals, oxidizing agents, organic materials, alkalis, and water.

Use common sense and extra caution to ensure that the hydrochloric acid does not react with the listed elements. If spill occurs ensure that the source of the spill is inactive. Next, dilute with water and mop up, or absorb with an inert dry material and place in an appropriate waste disposal container. If necessary, neutralize the residue with a dilute solution of sodium carbonate.

95% Ethanol (C2H5OH)


Ingestion: If victim is conscious and alert, give 2-4 cupfuls of milk or water. Never give anything by mouth to an unconscious person. Get medical aid. Induce vomiting by giving one teaspoon of Syrup of Ipecac.


Refer to copper chloride Refer to copper chloride

Hazards in presence of heat, sparks, and open flame.

In case of spill absorb material with suitable absorbent and containerize for disposal.

** Common to all chemical compounds: Long hair should be tied back to ensure that it does not come in contact with the flame or other chemicals. As well, to ensure that the hair does not promote lab accidents due to visibility impairment.

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Data Collection through Observation Qualitative Table:

Reaction

Qualitative description after close examination and

collective observation

Dehydrating Copper

Chloride Hydrate with the application of heat

from flame

The dehydration process for copper chloride hydrate was visibly apparent as the initially turquoise colored crystals had changed into a brown color after the application of heat for a few minutes. To ensure that all the water had evaporated the contents inside the crucible were massed, then subjected to heat, and again massed (3 times for accuracy). This is called heat to constant mass.

Hydrating Anhydrous Copper Chloride with

Distilled Water

The brown crystals, indicating the absence of H2O, were again mixed with distilled water. Upon contact with water the brown crystals began turning back into a turquoise color indicative of the rehydration process.

Aluminum Strip added into Copper Chloride

Solution

The aluminum strip in the copper chloride solution almost instantly produced bubbling, heat, and release of hydrogen gas. The reaction is an exothermic single displacement reaction. The reaction is represented by the chemical reaction below:

3CuCl2 + 2Al AlCl3 + 3Cu

Application of

Hydrochloric Acid in removal of Copper from

Aluminum Strip

After the reaction described above, HCl was applied to remove remaining fragments of the copper from the aluminum strip. Though HCl was applied using a dropper sparingly the reaction with the aluminum was nevertheless instant and intense; producing bubbles, hydrogen gas, and heat.

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Data Collection through Observation [Cont’d] Quantitative Table:

Chemical Compounds

& Equipment

Mass of Chemicals & Equipment (grams)

Methodology for

Determining Mass

Non- contaminated Crucible (without lid)

11. 84

Electronic Scale

{Step #2 in Procedure}

Copper Chloride Hydrate

1. 00

Electronic Scale


Copper Chloride Hydrate + Crucible

12. 84

Electronic Scale

Copper Chloride Anhydrous + Crucible

12. 65

Electronic Scale


Mass of Evaporated Water

0. 21

[Copper Chloride Hydrate +

Crucible] –

[Anhydrous Copper Chloride + Crucible]

Aluminum Strip

0. 25

Electronic Scale


Filter Paper

0. 52

Electronic Scale


Glass Disk

18. 42

Electronic Scale


Copper + Filter Paper + Glass Disk

19. 32

Electronic Scale


Copper

o. 38

[Copper + Filter Paper +

Glass Disk] –

[Filter Paper + Glass Disk]

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Data Processing and Analysis:

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Data Processing & Analysis Cont’d:

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Data Processing and Analysis:

The calculations shown above reveal that the formula of the unknown

copper chloride hydrate was, in fact, CuCl2 · 2H20.

The calculations from the previous pages will be interpreted and put into context in the following few paragraphs. The objective of this lab was to determine the formula of a copper chloride hydrate compound. The formula of Copper (II) Chloride Dihydrate was determined through a series of simple calculations to find the number of moles of each element in the compound. The

formula: n= was applied to solve for the number of moles of each element.

The molar mass of each element was obtained from the periodic table and the masses of each element were obtained during the experimentation. Next, the number of moles was determined for each element in the compound. Following those calculations, all the mole values were divided by the smallest of the mole values (copper’s mole value) to render whole numbers for each element; the molar ratio for chlorine and water were rounded in order to obtain whole numbers. This then resulted in the molar ratio of the compound; Copper: Chlorine: Water bond in a 1:2:2 ratio to form the Copper (II) Chloride Dihydrate compound. This ratio means that for every mole of copper there will be two moles of chlorine and water.

To support the above findings and the conclusive formula that has been calculated two additional sources have been gathered to verify the results.

Firstly, the oxidation states of copper were researched. This research revealed the common oxidation states of copper: the less stable copper (I) state,

Cu+; the more stable copper (II) state (which forms blue or blue-green salts and

solutions), Cu2+

. Furthermore, under unusual conditions, a Cu3+ state and even an

extremely rare Cu4+ state can be obtained. It is essential to note that Cu

2+ forms blue or blue-green salts and solutions, for the reason that after reviewing my qualitative table I made a startling correlation with the fact obtained from the research. In my table I had described the resulting solution after the reaction between the anhydrous copper chloride and water as being turquoise (blue-green) coloured. Also, from my research I had concluded that it was not possible for the unknown copper (II) chloride to be either in 3+ or 4+ state as they were both either rare or unusual examples. The common oxidation states of copper are 1+

and 2+, while Cu2+

is the more stable ion. Furthermore, Copper Chloride (I) is insoluble in water, however, it dissolves in aqueous solutions containing suitable

donor molecules. Since this lab experiment only involved unknown CuCl

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dissolving in distilled water, it was quite evident that CuCl1 was not the copper chloride involved in this lab. Therefore the research presented above further elucidated the fact that the unknown copper chloride involved in the lab

experiment was in fact CuCl2.

Secondly, the percentage error of the final calculations was performed to further support the validity of the final result. The introduction for this lab write-up contains a description for calculating percentage error. The theoretical yield for copper was approximately 0.37g and the actual yield was 0.38g. Thus, the percentage error was calculated to be approx.1.9%. This percentage proved that the lab experiment was conducted with a fairly high degree of accuracy, thus the results obtained were also very accurate.

If I were to repeat this experiment I would add a third additional source for verifying my results. I would run a test for copper (II) ions. I would add aqueous sodium hydroxide to the unknown copper chloride hydrate. This reaction would result in the production of a blue precipitate of copper (II) hydroxide.

Ionic equation:

Cu2+(aq) + 2OH−(aq) → Cu(OH)2(s)

The full equation:

[Cu(H2O)6]2+(aq) + 2 OH−(aq) → Cu(H2O)4(OH)2(s) + 2 H2O (l)

All the data presented above, together with its supporting sources utterly decrees that the chemical formula was

CuCl2 2H2O [Copper (II) Chloride Dihydrate].

http://en.wikipedia.org/wiki/Sodium_hydroxide

http://en.wikipedia.org/wiki/Copper(II)_hydroxide

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Cookbook:

final lab#1

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