CHEM101L Lab 7 F

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CHEM101L

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Chemistry

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Feb 20, 2024

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Lab 7 Precipitation Reactions CHEM101L Student Name: Ani Harutyunyan Access Code (located on the lid of your lab kit): AC-MD9MT9 Lab Report Format Expecta0ons U"lize college level grammar and professional forma4ng when comple"ng this worksheet. Report all equa"ons in a proper mathema"cal format, with the correct signs and symbols. Pre-Lab Ques?ons 1. What is percent yield and why is percent yield important to the field of chemistry? The yield in chemical factories oAen varies from theoreCcal predicCons due to factors like unaEainable ideal reacCon temperatures, product state, and reactant impuriCes, making the calculaCon of percentage yield vital for esCmaCng pracCcal output. 2. What informaCon would you need to calculate a percent yield? Percent yield is determined by mulCplying the raCo of actual yield to theoreCcal yield by 100. 3. Research some common precipitaCon reacCons online and list two, here. 1.AgNO3 - NOCI -• AgCI S) + NaNOS 2. BaCl2 + H2SO4 → BaSO4 (s) + 2HCl 4. Why is atomic mass significant to calculaCng percent yield? The atomic mass unit is useful for determining the number of moles in an atom, rather than just measuring its mass. CalculaCng the number of moles is a necessary step in the computaCon of percent yield.
Lab 7 Precipitation Reactions CHEM101L EXPERIMENT 1: TESTING FOR THE CALCIUM ION Introduc?on Ques?ons 1. In this experiment, you will test to see if the calcium ion is present in soluCon. How will you know if this is the case? The presence of calcium ions in a soluCon can be confirmed by the formaCon of a white precipitate when oxalate ions are added or by a red color in a flame test. 2. Under what condiCons do precipitates form during a chemical reacCon? A precipitate forms when a dissolved substance's concentraCon surpasses its solubility, which can occur by mixing two soluCons with ions that react to create an insoluble compound, altering the soluCon's temperature, or changing its pH. 3. What chemicals do you add to the test tube in Step 1 and Step 2 of this experiment? a. Step 1: Sodium Fluoride (NaF) Step 2: Calcium Acetate (Ca(C2H3O2)2)
Lab 7 Precipitation Reactions CHEM101L Data and Observa?ons Below, insert a photo of your test tube as soon as you mix the two chemicals together, before the precipitate forms. Your name must be included in the background for credit. Below, insert a photo of your test tube aAer the reacCon has completed. The precipitate must be clearly visible in the photo for credit on this lab. You must also include your name in the background of the photo.
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Lab 7 Precipitation Reactions CHEM101L Results and Discussion 1. In your own words define and describe the reacCon that occurred. 1 min. - No signs of precipitaCon; soluCon has a cloudy white/grey appearance 20 min. - A white, cloudy region forms at the test tube's base, indicaCng potenCal precipitaCon 30 min. - The boEom shows a more cohesive, gel-like precipitate forming 1 hr. - A solid, white opaque substance has seEled at the test tube's boEom 2. Write the reacCon equaCon that took place, below. Ensure that you note the state of the compounds where appropriate. Ca(C 2 H 3 O 2 )2(aq) + 2NaF(aq)—> CaF 2 (s)+ 2NaC 2 H 3 O 2 (aq) 3. Suppose you didn’t know that the original soluCon contained the calcium ion. From your results, how can you know that it did in fact contain calcium? Because of the presence of white calcium fluoride precipitate during the interacCon of calcium acetate with sodium fluoride which signifies that calcium ions were present in the iniCal soluCon. 4. What is the difference between Ca and Ca 2+ ? They are both calcium, but what makes them different? Ca: neutral calcium atom Ca 2+: posiCvely charged calcium 5. What is the chemical name (not the formula) for the precipitate formed during the reacCon? Calcium Fluoride