CHEM 112 : Lab Report 3.docx

Just need help with a few questions from my lab!

Lab Notes:

Experiment 1:

Tube 1: No bubbles produced

Tube 2: Bubbles produced, slowly and sporadically

Tube 3: Bubbles produced, quickly and constantly

Tube 4: Bubbles produced, slowly and sporadically

Tube 5: No bubbles produced

Optimum temp for catalase activity: 40 C

Experiment 2:

Tube 1: 4 min, 42.38 sec

Tube 2: 5 min, 4.37 sec

Tube 3: 5 min, 18.26 sec

Tube 4: 5 min, 28.36 sec

Concentration: 10 mL 3% hydrogen peroxide

Experiment 3:

Tube 1: No bubbles produced

Tube 2: Bubbles produced, quickly

Tube 3: No bubbles produced

Optimum pH for catalase activity: pH 6 buffer

Lab Questions

Experiment 1:

1. Why did catalase fail to function at 80 °C?

2. What caused the bubbles to form when you added the catalase to the hydrogen peroxide and water mixture at 40 °C?

A. Catalase activity heated the solution to its boiling point.

B. Hydrogen gas formed during the formation of hydrogen peroxide.

C. Oxygen gas formed during the decomposition of hydrogen peroxide.

D. The constant temperature bath heated the solution to its boiling point.

Experiment 2

3. Before the catalase concentration was saturated with hydrogen peroxide, why did the enzyme function vary with substrate concentration?

4. Why did the catalase function level off when different hydrogen peroxide concentrations were tested?

Experiment 3

5. Why did catalase only function in a limited range of pH values?

6. Based on your results from this lab, would you expect the hydrogen peroxide you buy from the store to bubble like soda when you open it?

1.A block of metal has dimensions 5.00 cm x 2.50 cm x 3.00 cm. Calculate the volume of the block, showing the answer to the correct number of significant figures and unit.

2.If the block of metal from question 2 has a mass of 405.3 g, what is the density of the metal? Calculate the density, showing the answer to the correct number of significant figures and correct unit.

3.Convert the numerical value of the density in question 2 from units of grams per cubic centimeter (g / cm3) to milligrams per milliliter (mg / mL). Note:

-there are 1000 milligrams in a gram.

-the volume unit cubic centimeter cm3 equals the milliliter mL.

Keep the new density to the same significant figures as you reported in question 2

4.A finely-powdered white solid is known to be homogeneous mixture rather than a pure substance. A sample of this solid completely dissolves in water. Give TWO possible substances that could make up this solid mixture, and briefly explain your choices.

5.If your percent SALT in Lab 2 is relatively low, it can be assumed that some salt did not go into the filtrate (the liquid that passes through the filter paper), but rather may have been trapped with the sand. Explain briefly how you could recover any of this "missing" salt?

6.A brand of aspirin claims to contain 325 mg (1 g = 1000 mg) of aspirin per tablet. In addition to pure aspirin, a tablet also contains a non-active filler. We assume that the tablet contains only these two components: aspirin and filler. If a single tablet weighs 1.17 g, calculate the percent filler. Hint: calculate percent aspirin FIRST using the formula

% aspirin = [ (mass aspirin ÷ mass tablet) x 100], the find % filler. When using this formula, make sure the masses of aspirin and tablet have the same units.

7.Water has a density of 1.00 g/mL, and chloroform has a density of 1.49 g/mL. These two liquids do not mix with each other, but rather, form two layers when combined.

8.Equal volumes of water and chloroform are placed in a beaker. A piece of nylon is dropped in the beaker, and is seen to float the the interface (the boundary) of the two liquid layers.

Give a possible value for the density of nylon, including the correct units. Explain your answer briefly.

9.A procedure similar to that used in Lab 3 was performed to find the density of cyclohexane, which has an actual density of 0.779 g/mL, Due to poor lab technique, an experimental density of only 0.663 g/mL is found. Calculate the percent error for the density. Give your answer to the correct number of significant figures.

10.Two white powders are given to you. One is pure sodium bicarbonate, and the other is baking powder (a mixture of sodium bicarbonate and a weak acid like citric acid). Which single test (NOT counting the visual examination with a hand lens) used in Lab 3 allows you to distinguish sodium bicarbonate from baking powder? Explain your answers completely.

11.Gold has a specific heat of 0.129 J/g^oC. If a piece of gold (initially at 10.0^oC) is dropped into hot water, the final temperature of both the gold and the water is measured as 70.9^oC. If it is known that 4560 J of heat transferred from the hot water to the gold, what is the mass of the piece of gold in grams? Give your answer to the correct number of significant figures.

12.It is stated in the Introduction to Lab 4 that q_water = -q_metal. This equation means that if a hot piece of metal is placed in water, the amount of heat given off by the metal is exactly equal to the amount of heat absorbed by the water. However, this equation is not always accurate, because not all of the heat from the metal necessarily goes to the water. Where else can some of the heat go if it is not absorbed by the water?

13.A certain brand of breakfast cereal claims to have 100 Calories per 28 gram serving. 150.0 grams of cereal are burned using a procedure similar to that used in Lab 4. How many calories of heat are released? Note 1 food Calorie (capital C) = 1000 heat calories (lower case c)

14.The oxalate anion C2O42- is found in many dark green vegetables, including spinach, swiss chard, and collard greens. When cations react with oxalate, the resulting ionic compounds are insoluble in water except Group I A oxalates (e.g. compounds of lithium, sodium, potassium, etc. and oxalate) and ammonium oxalate (NH4)2C2O4. These exceptions are soluble in water.

15.Spinach leaves are cut into small pieces, mashed with small amounts of boiling water, and filtered through filter paper to remove the insoluble spinach material. The resulting aqueous extract contains the oxalate anion.if a small amount of the spinach extract is mixed with a small amount of a calcium acetate solution, Ca(C2H3O2)2(aq), what do you expect will be observed?

16.If a small amount of the spinach extract from question 16 is mixed with a small amount of a potassium acetate solution, KC₂H₃O₂(aq), what do you expect will be observed?

17.If a hot water extract of another vegetable is mixed with calcium acetate solution and a white precipitate is observed, does this automatically indicate the presence of the oxalate anion in this vegetable? Explain your answer.