Chemistry 12 Lab

Ashwin’ s Chemist ry 12 Lab Book Course: SCH4U Teacher: Mr. Linzel

2008 Electronic Document

Introduction The lab we are doing is a review of the Grade 11 unit Quantities in Chemical Formulas. To understand this lab, we must know the basics first. We know that atoms, ions and molecules are too small to see and that observable changes in chemical reactions must involve extremely large numbers of these entities. To count these large numbers, a precise and convenient way has been formulated to determine their mass. This is called the mole. This is the number used by chemists to define numbers of entities as small as atoms (SI symbol, mol). A mole is the amount of substance containing 6.02x1023 of anything. This is knownas Avogadro’s constant. We have been familiarized by solving for the variables of molar mass, number of moles or mass by using the equation:

n=m M n= number of moles m= mass M= molar mass Stochiometry is the relationship between quantities of reactants and products that are involved in chemical reactions. Stochiometry is a very important in the fields of industry, medicine and ecology. We also know that you must balance out formulas for reactions. This is due to the fact that the mass of the products in a chemical reaction is always equal to the mass of the reactants which is stated by the Law of conservation of mass. Stochiometry is very important because it helps us determine empirical formulas, which are the simplest forms of the chemical reaction. Ex. Na + O2  NaO

2Na + O2  2NaO

This is an obvious example of law of conservation of mass. If we look at the first part of the reaction, we know that we cannot leave the equation like that. This would mean that 2 parts of oxygen had been reacted to form one part of oxygen. This would mean that one part of oxygen is missing. In accordance to the law of conservation of mass, we know this is false. Therefore when we balance the equation as shown in the next step, the number of each reactant is the same as the number of each product. For this lab, we must be able to tell if a chemical reaction or a physical reaction is occurring. To know this we can tell which type of reaction is occurring by what is happening in the reaction. We know that for chemical reactions a new substance is 2 | Page

created. Indicators of a chemical reaction taking place are appearance, texture, color, odor, melting point, boiling point, density, solubility, and polarity. Physical reactions are reactions that simply change the state of the matter. Physical reactions are reversible. An example is water turning to ice by the process of freezing.

Purpose Determine the formula for a copper chloride hydrate compound; including the moles of the hydrate.

Hazardous Material Assessment Copper Chloride - Copper Chloride is hazardous to eyes and can cause irritation to eyes, skin, and respiratory tract and gastro intestines. Chopper Chloride should always be kept in a tightly closed container. To dispose of this sample, follow federal, state and local regulations.

Ethanol- Exposure over 1000pm of ethanol may cause headaches, irritation of eyes, nose and throat. If ingested, it may cause blindness. Ethanol should be kept in a cool, ventilated area which is kept away from heat. Oxidizing materials and strong acids should be kept away from it. Ethanol should be disposed according to state regulations.

Hydrochloric Acid- Hydrochloric acid causes severe burns and may be fatal if inhaled or swallowed. The vapor produced from the acid, is extremely irritating. It can cause damage to the respiratory passages and lungs, irritation to the eyes, skin, respiratory tract and gastrointestinal discomfort. Hydrochloric acid should be kept in a container that is 3 | Page

tightly sealed in a well ventilated area away from incompatible materials. Hydrochloric acid should be disposed in accordance with all applicable federal, state, and local regulations.

Procedure 1. Gathered required materials from materials list. 2. Used an electronic balance scale to mass, in grams, a pure crucible. Had used Sig Figs at two decimal points. 3. 1.00 gram of Copper Chloride Hydrate was massed in a crucible on the electric balance scale. Data was recorded in data table. 4. Used a clay triangle to support the crucible contacting the copper chloride hydrate. Clay triangle was supported by an iron ring attached to the retort stand. This allowed the crucible to be stable over the Bunsen burners flame. 5. Carefully lit the Bunsen burner and left a distance of 5-7 cm from crucible. 6. Had gently heated the crucible so that the green crystals had changed to a brown color. This had identified evaporation of the hydrate from Copper Chloride. 7. Sample was left to cool before being massed. Once the sample had cooled, the mass of the crucible in grams was recorded in data table. Mass of evaporated water was found by simply subtracting mass of the crucible by itself. 8. Transferred the brown crystals (anhydrous copper chloride) in the crucible to a 50 ml beaker. Had rinsed out the crucible with 16 ml of distilled water. The brown crystals had dissolved in the distilled water by doing this. 9. The beaker was then swirled around to ensure that all crystals of copper chloride were properly dissolved. 10. Placed a strip of aluminum wire of a mass of 0.25 grams into the beaker. 11. Observed the reaction between the aluminum wire and the copper chloride. Observations were recorded in table. 12. A few drops of 6M of HCl were applied to dissolve remaining insoluble aluminum salts. 4 | Page

13. Had used filter paper and folded it evenly twice to take the shape of the funnel. The funnel was then placed inside a beaker. 14. Had carefully poured the solution into the funnel allowing it to filter into the beaker. This had ensured that the copper chloride would remain in the filter paper. 15. Had placed a few drops of ethanol into the gravity filter to ensure only copper was left in the filter. 16. Had taken the filter paper with the copper intact and placed it on a glass disk in the incubator to dry. 17. Had then massed the filter paper with the copper on it. Had then subtracted the mass of the filter paper from the total mass to get the reaming mass of the copper in grams.

Table of Materials and Equipment Materials and Equipment Hydrochloric acid (HCl) Copper Chloride Hydrate 95% Ethanol (C2H5OH) Retort Stand Crucible Electronic Scale Clay Triangle Graduated Cylinder Beaker Glass Funnel Filter Paper Lab Goggles Pipette Aluminum Wire

Amount 6M 1.00g 10 Ml 1 1 1 1 1 1x 50 ml 1 1 1 1 1

Data Table 5 | Page

Chemical Compounds & Equipment

Pure Crucible Copper Chloride Hydrate Copper Chloride Hydrate + Crucible Copper Chloride Anhydrous + Crucible Mass of Evaporated Water

Mass of Chemicals and Equipmen t (grams) 11.84 1.00 12.84 12.65 0.21

Aluminum Strip

0.25

Filter Paper

0.52

Glass Disk

18.42

Copper + Filter Paper + Glass Disk Copper

19.32 0.38

Qualitative Table Qualitative Observations Process Dehydrating H2O from Copper Chloride

While dehydrating the water from the copper chloride, the sample had started to turn a brownish color. As the time increased, the green crystals started becoming less visible. This was due to the heat from the Bunsen burner. Once all the crystals in the sample were brown, it was massed three times to make sure it had reached a constant mass.

Hydrating Anhydrous Copper Chloride

The brown Crystals were again mixed 6 | Page

with Distilled Water

with distilled water. As this was done, the brown crystals had turned back to a turquoise color indicating the sample was rehydrated.

Adding an Aluminum Strip to the Solution

When the aluminum strip was placed in the copper chloride hydrate water solution, it instantaneously reacted. Bubbles and gas were visible during the reaction which also releaseda fair amount of heat. This process had produced a single displacement reaction:

3CuCl2 + 2Al  2AlCl3 + 3Cu

Removing Copper from Aluminum Strip with HCL

The use of hydrochloric acid was involved to remove any copper that had still remained on the aluminum foil. The HCl had reacted very fast with the aluminum strip producing fizzing and hydrogen gas.

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Data Analysis Through the use of Stochiometry, the calculations state that the empirical formula of the unknown copper chloride hydrate was CuCl2 · 2H2O This empirical formula was found by using the basic equation to find the number of moles of chlorine, water and copper. You then take the number of moles and divide it by the lowest number of moles. This gives you the number of moles in proportion to one mole of the smallest molar volume. Since Copper is a multivalent atom. It can have a charge of +1 or +2. In this lab we were not told which copper we were using which means we had to analyze the reactions and decide which copper would fit. CuCl would not fit the reaction due to the fact that if CuCl was placed into distilled water, it wouldn’t dissolve. Also it would definitely not change color due to it not dissolving. We know that CuCl2 would dissociate since it was in an aqueoussolution. From this previous knowledge we can conclude that it we had used CuCl2 in this reaction. The formula mass was taken

was used to find the number of moles of each substance. The

from the data table and the molar mass was taken from the periodic table of elements. This had concluded that the values were 1 for copper and 2 for chlorine and water. Therefore the ratio was 1:2:2 in the copper (II) chloride dehydrate compound. To figure out where sources of error may exist, the equation to calculate Percentage error was used.

We use this equation by taking the theoretical yield of copper which was 0.37g subtract to the actually yield of 0.38g. This is then divided by the theoretical yield and multiplied by 100 to give you a percentage of error. This had proven that the 9 | Page

percentage error in this lab was 1.9%. This is a very low percentage and means that the amount of error was low and that the experiment was done to a successful standard.

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