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Catalyst

Catalyst. Get calculators and notes ready for today! 1. Write down one highlight from your weekend. 2. If you have to start with 3 moles of Fe 2 O 3 , how many grams is this?. Today’s Agenda. Baking Soda and Vinegar Lab.

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Catalyst

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  1. Catalyst Get calculators and notes ready for today! 1. Write down one highlight from your weekend. 2. If you have to start with 3 moles of Fe2O3, how many grams is this?

  2. Today’s Agenda

  3. Baking Soda and Vinegar Lab • The reaction you will be working with should be familiar to you from elementary school science fair volcanoes: You will be mixing baking soda (NaHCO3) with vinegar (CH3COOH) to generate carbonic acid (H2CO3, which breaks up into water and carbon dioxide gas) and sodium acetate (NaCH3COO), which is a food preservation additive. • NaHCO3 + CH3COOH CO2 + H2O + NaCH3COO • NaHCO3 = baking soda • CH3COOH = vinegar

  4. Amount of Baking Soda • For our reaction, we will need to use 0.01 moles of baking soda, which we will call by its chemical name, sodium hydrogen carbonate, for the rest of this lab. If we use much more than 0.01 moles of baking soda, the reaction will be too large and we won’t have time to complete the reaction once we mix it with the vinegar (which we will call acetic acid). • NaHCO3 + CH3COOH  CO2 + H2O + NaCH3COO • How many grams of NaHCO3 will we need if we need 0.01 mol?

  5. Step 1: Let’s weigh it out! • Group 1: mass 0.84 grams of baking soda

  6. Step 2 • Group 2: Dissolve the sodium hydrogen carbonate (baking soda) in about 6 milliliters of water. Stir the solution until most or all of it is dissolved (if a little won’t dissolve, that’s OK).

  7. Step 3 • Group 3: Weigh a 250 mL flask. We will need the weight of the empty flask at the end of the lab. Initial mass of flask: _______ • Now add the sodium hydrogen carbonate solution to the preweighed250 mL flask.

  8. Step 4 • Group 4: Obtain 30 mL of acetic acid (a.k.a. vinegar) and slowly add it to the sodium hydrogen carbonate solution. You will observe the formation of bubbles when the acetic acid is added to the sodium hydrogen carbonate solution. Wait until the bubbling subsides before adding more acetic acid. When all of the acetic acid has been added, we will stir for one minute before moving on to step 5.

  9. Step 5 • Group 5: When the solution is again calm (there may be a few bubbles rising from the bottom of the flask - this is normal), move the flask to a hot plate and heat it to boiling. Be careful that the flask does not boil over because this will cause errors in our calculations. Once the flask has started boiling, gently set a watch glass on its mouth to keep any of the liquid inside from splattering.

  10. Step 6 • Group 6: When all of the liquid in the solution has boiled away, remove the flask from the hot plate. The powder that you observe inside is the product of the reaction, sodium acetate. Once the flask has had a few minutes to cool down to room temperature, measure and record its weight. • Final mass of flask and product: ________

  11. Today’s Agenda

  12. Grams Substance A Moles Substance A Moles Substance B Grams Substance B Molar Mass Molar Mass Mole Ratio Theoretical Yield • If we started with 0.84 g of NaHCO3, how many grams of NaCH3COO were we supposed to get? • This is our theoretical yield.

  13. Actual Yield • We can find the mass of how much NaCH3COO we actually got out of the reaction. We have the mass of the flask plus whatever NaCH3COO we collected, and we have the mass of the empty flask. How can we find the mass of just the NaCH3COO? • Final mass of flask and product – initial mass of flask = mass of product: ________________ • This is our actual yield.

  14. Percent Yield • We can find the percent yield by doing the following: • Actual yield/theoretical yield * 100 = percent yield

  15. Sources of Error • Do you think it is common for scientists to get 100% yield? • Why or why not? • What sources of error could there have been?

  16. Today’s Agenda

  17. Exit Slip • 1. In your own words, explain what theoretical yield is. • 2. In your own words, explain what actual yield is. • 3. In your own words, explain one source of error that can cause us not to get 100% yield when we do experiments.

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