In a chemistry class, a student is asked to mix 20% of solution A with water to makes 8 cups of 15% solution mixture. How many cups of solution A and how many cups of water do the student need to complete the required mixture?

Briefly explain how each of the following errors in the experimental procedure would affect the calculated mass percent Co in the analyzed sample of cobalt (II) nitrate. Although a student added 25 mL of deionized water to cups A-E, he mistakenly added only 20 mL of water to cups 1-3.

A.) cant be determined

B.) stay the same

C.) Incorrectly high

D.) Incorectly low

Experiment 1: Grind Size

For each treatment (coarse, medium fine):

1. Weigh 35g of coffee for each treatment (coarse, medium, fine) and add it to each French press.

2. On the stove, heat 5 cups of water to 85°C.

3. Quickly pour 1 ½ cups water into each French press. Be careful! The glass will be HOT.

4. Stir each mixture twice with a spoon and brew for 4 minutes, using a timer.

5. After 4 minutes, slowly press the plunger and pour coffee into cups.

6. Evaluate all treatments at the same time, when they are cool enough to taste. Each student should take 3 Styrofoam cups and rinse them after each experiment.

7. Pour any remaining coffee down the sink, and scrape the grounds out into the trash with a spoon.

Experiment 2: Temperature

For each treatment (70°C, 85°C and 100°C):

1. Weigh 35g of medium grind coffee for each treatment and add it to each French press.

2. On the stove, heat 3 batches of 2 cups of water to 70°C, 85°C and 100°C.

3. Quickly pour 1 ½ cups water into each French press. Be careful! The glass will be HOT.

4. Stir each mixture twice with a spoon and brew for 4 minutes, using a timer.

5. After 4 minutes, slowly press the plunger and pour coffee into cups.

6. Evaluate all treatments at the same time, when they are cool enough to taste. Each student should take 3 Styrofoam cups and rinse them after each experiment.

7. Pour any remaining coffee down the sink, and scrape the grounds out into the trash with a spoon.

Experiment 3: Contact Time

For each treatment (2 minutes, 5 minutes, 8 minutes):

1. Weigh 35g of coffee of medium grind coffee for each treatment and add it to each French press.

2. On the stove, heat 5 cups of water to 85°C.

3. Quickly pour 1 ½ cups water into each French press. Be careful! The glass will be HOT.

4. Stir twice with spoon and brew for each treatment time, using a timer.

5. After each treatment time, slowly press the plunger and pour coffee into cups.

6. Evaluate all treatments at the same time, when they are cool enough to taste. Each student should take 3 Styrofoam cups and rinse them after each experiment.

7. Pour any remaining coffee down the sink, and scrape the grounds out into the trash with a spoon.

1. In this lab we explored a number of ways to alter coffee extraction efficiency. If you brewed a weak cup of coffee, describe how you would increase the flavor strength of the next batch using insight you gained from the three experiments in today’s lab. Explain why each method would increase your coffee flavor strength. (6 pts)

2. What flavor profile can you expect from coffee that was brewed using an excessively long contact time between the coffee and water? Why? (4 pts)

3. What flavor profile can you expect from coffee that was brewed using beans that were ground too coarsely? Why? (4 pts)

4. We used a burr grinder to grind the beans for today’s lab. Describe how a burr grinder works (what are the parts, how does this control particle size?), and how it is different from a common propeller grinder? Aside from the particle size, what other detrimental effect can a propeller grinder have on the ground coffee? What affect do these factors have on extraction during brewing? (6pts)

Mark the cups as "Pure Juice," ½, ¼, 1/8, 1/16, and"Control."

Into the "Pure Juice" cup, put 4 oz of pure fruit juice.

Put another 4 oz of the pure fruit juice into a measuring cup, andadd enough water to bring the volume to the 8 oz level. Stir themixture thoroughly.

Transfer half the solution to the cup marked ½ .

To the remaining solution in the measuring cup add enough water tobring the volume to the 8 oz level.

Stir the mixture thoroughly, and transfer half of it to the cupmarked ¼.

Use this same procedure to make up dilute solutions for the 1/8 and1/16 cups.

Put 4 oz of pure water into the cup labeled "Control."

Poke a hole in the center of each piece of plastic wrap, fastenthem to the tops of the cups by using rubber bands, and insertPopsicle sticks.

Put all six cups into the freeze at the same time. Every half hourcheck on the freezing process. Look through the wrap and stir tosee whether it is frozen. Record the time in the Table at whicheach fruit pop was completely frozen.

Cup

Control Time required to freeze, hr


½


¼


1/8


1/16