Salt Water Mixture Percent Yield - West Linn-Wilsonville School District

WLHS / Conc Chem / Monson Name

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LAB ACTIVITY: Salt Water Mixture and Percent Yield

PRELAB:

1) What does percent mean?

Example #1: What percent of this class is 15 years old?

2) What does yield mean?

Example #2: Last year, a local farmer had a yield of 90 kilograms of grapes.

What if this farmer expected to grow 110 kilograms of grapes on that piece of land? Was this a good year or a bad year? How do you know?

3) What would % yield mean? Show work for calculating % yield for example #2.

Example #3: What if the farmer had actually produced 120 kilograms instead? Was this a good year or bad year?

Show work for expressing it in percent yield.

ACTIVITY Directions:

1) Put about 2 grams of salt in your evaporating dish, recording the exact mass of your salt below.

Mass of empty evaporating dish: Mass of evaporating dish and salt: Mass of salt (SHOW work!):

2) Put about 25 mL of water in your evaporating dish. Stir or swirl until all the salt dissolves. 3) Look at your water and salt. Is this mixture Homogeneous or Heterogeneous? Explain how you know.

4) Write the Chemical Formula for each substance: Salt: Water

5) Place your evaporating dish on the hot plate. Set the temperature dial to its maximum setting. Maintain a slow, steady even boil until all the water has evaporated.

6) Is dissolving the salt a chemical or physical change? Explain why you think so.

7) After your dish has cooled, measure the mass of your evaporating dish with the salt dried in it.

Mass of empty evaporating dish (from above):

Mass of evaporating dish and recovered salt:

Mass of recovered salt (show work):

8) To find % yield, you will find out how much salt you recovered compared to what you put in at

the beginning. The formula is....(then plug in your numbers for salt and solve!)

% yield =

Actual x 100 =

Theoretical

x 100 =

9) How could you get a better percent yield in this experiment?

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