74 EXPERIMENTS IN GENERAL CHEMISTRY Most of the copper containing salta used in

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74 EXPERIMENTS IN GENERAL CHEMISTRY Most of the copper containing salta used in this experiment contain only one copper atom per formula unit and therefore, n 1 for most unknowns. Your laboratory instructor will tell you if your compound contains more than one copper atom per formula unit. Y ou wil use the experimentally determined percent copper and the value of n to calculate the weight of the salt in the above relationship, CAUTION YOU MUST WEAR DEPARTMENTALLY APPROVED EYE LABORATORY KEEP ALL OTECTIONATALLTIMES YOU ARE IN THE PR REACTION VESSELS WELL AWAY FROM YOUR FACEM PROCEDURE Step 1. ve your laboratory instructor a clean test tube in exchange for a test tube containing ly two grams of an unknown copper compound. Record the Identity Number of the "Unknown" on the REPORT FORM (1). Step 2. Wash two 150 mL beakers and rinse them with distilled water. Step 3. Weigh the test tube an total Unknown to the nearest 0.001 g. Record this mass on the REPORT FORM (3 Step 4. Tap (shake) about half of the Unknown Sample into one of the 150 mL beakers. Label this beaker Step 5 Weigh test the remainder of the Unknown to the the and record this value on the The difference in weights from Step 3 and 5 will be the weight of the Unknown in the beaker 1" REPORT FORM (21). Step 6. Empt the remainder of the unknown into the second 150 mL beaker. Label this the empty test tube to the nearest o.001 g. Record this mass on the Step 7. REPORT (T) INOTE: The difference in the weights from Step 5 and will be the igens of the Unknown in the beaker "#2." REPORT FORM (21). Step 8. Place a etirring rod fitted with a rubber tip(rubber policeman) in each beaker. (NOTE: Leave each stirring rod in its own beaker for rest of the experiment Step 9. Add about 50 mL of distilled water to each beaker. (NOTE: Pour the stirring rod held low in the beaker to prevent splashing.) CAUTION! Hci A CID. USE LARGE AMOUNTS OF wASH AREAS oF coNTACT SPILL ANY ON YOURSELF. REPORT SPILLs To YOUR INSTRUCTOR IMMEDIATELY GAS IS USE A wELL VENTED HooD AND KEEP FLAMEs FROM THE VICINITY OF THE REACTION. AWAY Step 10. Add 5 mL of 6 M Hcl to each beaker. stir until the solid salt has dissolved (NOTE: If solid remains after stirring, add 6 M Hcl in 2 mL increments. Stir at least one minute after each Hol addition until the solid dissolves. Avoid adding a large Hcl.

Explanation / Answer

1. (a) The solid that is remained at the bottom of the beaker will not react with Mg and as a result calculated amount od Cu will be less.

(b) Ash from burning of filter paper will add up to mass of copper and the calculated amount will be more than actual value.

(c) Cu^2+ will not be displaced completely and calculated amount will be less.

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