NAME:______STATION:______PERIOD:______LAB “Mass Relationships in Chemical Reactions”

PURPOSE: To observe mass relationships in chemical reactions

MATERIALS:

triple beam balance 150-mL beaker 2 small test tubes 0.1 M sodium phosphate [Na3PO4] mossy zinc 0.1 M nickel(II) nitrate [Ni(NO3)2] 3.0 M hydrochloric acid (HCl) medium test tube watch glass 9-volt battery steel wool

PROCEDURE: Part A

1. Obtain 2 small test tubes and place them in a 150-mL beaker. Add 20 drops of sodium phosphate to one test tube and 20 drops of nickel(II) nitrate to the other. Place the beaker and test tubes in the center of the pan on a triple beam balance. Record the mass of this system (“before the reaction”) in the data table below.

2. Leave the beaker on the balance and carefully pour the contents of one of the test tubes into the other, and place the empty test tube back in the beaker. (If any spills occur, be sure that they are inside the beaker.) Record your observations below:

What type of substance was formed in this reaction? ______

Hypothesis: What do you think happened to the mass of this system after the reaction occurred? (Circle one of the options below.)

The mass of the system (increased / decreased / remained the same).

3. Record the mass of the system (“after the reaction”) in the data table below:

Mass of System Before the Reaction Mass of System After the Reaction

4. Was your hypothesis correct? ______

5. Complete and balance the following reaction:

Na3PO4 + Ni(NO3)2 → ______+ ______

What type of reaction is this? ______

6. When a chemical reaction occurs, the mass of the substances reacted must always equal the mass of the substances produced. What is this law called? ______

PROCEDURE: Part B

1. Obtain a 150-mL beaker and place it on the pan of the balance. Add approximately 2 mL of 3M hydrochloric acid to a medium test tube and place it in the beaker. In addition, place a small piece of mossy zinc on the pan of the balance. Record the mass of this system (“before the reaction”) in the data table below.

2. When the zinc is added to the hydrochloric acid, a chemical reaction will occur.

Hypothesis: What do you think happened to the mass of this system after the reaction occurred? (Circle one of the options below.)

The mass of the system (increased / decreased / remained the same).

3. Keep the beaker on the pan of the balance and add the zinc to the test tube. Record your observations:

What type of substance is being formed in this reaction? ______

4. After approximately 3 minutes, record the mass of the system (“after the reaction”) in the data table below:

Mass of System Before the Reaction Mass of System After the Reaction

Was your hypothesis correct?______

On the surface, this reaction appears to contradict the law of conservation of mass; however, we know that this cannot be true. Explain what happened: ______

______Complete and balance the following reaction:

Zn + HCl → ______+ ______

What type of reaction is this? ______

PROCEDURE: Part C

1. Obtain a watch glass a place it on the pan of the triple beam balance located in the fume hood. In addition, obtain a piece of steel wool (weighing approximately 1.5 g) from your instructor. Pull apart the steel wool sample slightly to give it more surface area, and place it on the watch glass. Record the mass of this system (“before the reaction”) in the data table below.

2. When the steel wool is ignited, a chemical reaction will occur.

Hypothesis: What do you think happened to the mass of this system after the reaction occurred? (Circle one of the options below.)

The mass of the system (increased / decreased / remained the same).

3. Touch the terminals of a 9-volt battery to the steel wool. Record your observations below:

4. After the reaction is complete, record the mass of the system (“after the reaction”) in the data table below:

Mass of System Before the Reaction Mass of System After the Reaction

Was your hypothesis correct?______

On the surface, this reaction appears to contradict the law of conservation of mass; however, we know that this cannot be true. Explain what happened: ______

______Complete and balance the following reaction:

(Note: the charge on the iron in the resulting compound is +3)

Fe + ______→ ______

What type of reaction is this? ______

CONCLUSION:

The most important thing to remember from this lab: (Circle one of the options below.)

During a chemical reaction, the mass of the reactants is always (greater than / less than / equal to) the mass of the products.