Explore BrainMass

Conservation of Mass

This content was STOLEN from BrainMass.com - View the original, and get the already-completed solution here!

Demonstrating conservation of mass through 2 chemistry lab experiments

Procedure 1

Empty test tube- 18.200g
Closed test tube- 19.128g
Vinegar (5ml)- 23.213g
NaOH (5ml)- 23.283g
Closed tube of NaOH (5ml)- 24.211g

1. Record the following masses in grams:

(a) an open, empty test tube:

(b) a closed, empty test tube:

(c) the test tube containing 5 mL vinegar:

(d) the test tube containing 5 mL sodium hydroxide:

(e) the closed test tube after the reaction:

2. Calculate and record the combined mass of the reactants vinegar and sodium hydroxide (in grams).

3. Calculate and record the mass of the contents of the test tube after the reaction (in grams).

4. Compare the two masses before and after the reaction. Calculate the percent deviation between the original mass and the measured mass after the reaction, which is defined as:

percent deviation = |(mass before reaction) - (mass after reaction)| / (mass after reaction * 100%)

According to the law of conservation of mass, we expect the percent deviation to be zero, but experimental measurements rarely give perfect results. The percent deviation is an indication of how well the experiment conforms to our expectations.

5. Explain what may have caused any discrepancy between the two values of the masses and whether you have confirmed the law of conservation of mass.

Procedure 2
Empty flask- 91.780g
Closed empty flask- 96.548g
Flask w/ Alka seltzer powder(1g)- 97.548g
Empty flask2- 91.780g
Flask2 H2O(40ml)- 131.780g
Flask2 H2O(40ml)+Alka seltzer powder(1g)- 137.548g
Assignment 1 of Procedure 2

1. Record the following masses, making sure to use the correct number of significant digits:

(a) mass of an open, empty flask (g)

(b) mass of a closed, empty flask (g)

(c) mass of a closed flask plus 1g Alka Seltzer powder (g)

(d) mass of an open flask with 40 mL water (g)

(e) mass of the closed flask with 1g Alka Seltzer and 40 mL water, after the reaction (g)

2. Calculate the combined mass of the reactants, Alka Seltzer and water (g)

3. Calculate the mass of the contents of the flask after the reaction.

4. Compare the two masses, before and after the reaction. Calculate the % deviation as:

% deviation = |(mass before reaction) - (mass after reaction)| / (mass after reaction) * 100%

5. Explain what may have caused any discrepancy between the 2 masses, and whether you have proved the law of mass conservation.

© BrainMass Inc. brainmass.com October 17, 2018, 10:10 am ad1c9bdddf


Solution Preview

Both experiments are very similar to each other, so I will explain the general concepts followed by a discussion for each question as it applies to both experiments.

The law of conservation of mass states that the amount of matter going into a reaction (of which matter has mass) should be exactly the same as the amount coming out of a reaction. By extension, so should the masses. To illustrate, imagine taking two Lego structures and deconstructing both of them and using all the building materials to build one new structure. Since you're using all the blocks from the original structures, your new structure should be the same mass as the sum of both the original structures. The same applies, but with atoms and molecules undergoing a chemical reaction.

Both your experiments put this fundamental law to the test. In the first case, you're working with a simple neutralization reaction between an acid and a base. Your acid is vinegar, your base is the sodium hydroxide.

CH3COOH (acetic acid in vinegar) + NaOH <--> H2O + NaCH3COO

In the second experiment, water becomes a solvent for the components of the Alka seltzer to react in. For the purposes of this question, the equation of the reaction isn't necessarily important, but for curiosity's sake:

C6H8O7 (citric acid) + 3NaHCO3 (sodium bicarbonate) ? 3H2O + 3CO2 + Na3C6H5O7

What's ...

Solution Summary

The following posting discusses problems that involve the law of conservation of mass.

Similar Posting

Velocity, conservation of momentum, force, force of gravity

1. A ball is thrown in the air with enough force so that it goes straight up for several seconds.
a. What is the velocity of the ball 1 sec before it's highest point?
b. What is the change in velocity during this 1 sec interval?
c. What is the velocity 1 sec after it reaches it's highest point?
d. what is the change in velocity during this 1 sec interval?
e. What is the change in velocity during the 2 sec interval?
f. What is the acceleration of the ball during any of these time intervals and at the moment the ball has a zero velocity?

2. An airplane is flying horizontally with speed 1000 km / h ( 280 m/s) when the engine falls off. Neglecting air resistance, if it takes 30 sec for the engine to hit the ground:
a. How high is the plane?
b. How far horizontally will the engine travel while it falls?
c. If the airplane somehow continues to fly as if nothing happened, where is the engine relative to the airplane at the moment the engine hits the ground?

3. A bicycle has wheels with a circumference of 2m. What is the linear speed of the bicycle when the wheels rotate at 1 revolution per second?

4. Before going into orbit, an astronaut has a mass of 55kg, While in orbit, a measurement determines that a force of 100N causes her to move with an acceleration of 1.90 m/s2. to regain her original weight, should she diet, or eat more?

5. A railroad car weighs four times as much as a freight car. If the railroad car coasts at 5 km/h into the freight car that is initially at rest, how fast do the two coast together after they are coupled?

6. A 60kg skydiver moving at terminal speed falls 50m in 1 sec. What power is the skydiver expending on the air?

7. To tighten a bolt, you push with a force of 80N at the end of a wrench handle that is 0.25m from the axis of the bolt:
a. What torque are you exerting?
b. If you move your hand to 0.10 from the bolt, what force do you have to exert to achieve the same torque?
c. Do your answers depend on the direction of your push relative to the direction of the wrench handle?

8. The value of g at the earth's surface is about 9.8m/s2. What is the value of g at a distance from the earth's center that is 4 times the earth's radius?

9. A 3 kg newborn at the earth's surface is gravitationally attracted to earth with a force of about 30N.
a. Calculate the force of gravity with which the baby on earth is attracted to the planet Mars, when Mars is closest to earth. (The mass of Mars is 6.4 x 1023 kg, and it's closest distance is 5.6 x 1010 meters)
b. Calculate the force of gravity between the baby and the physician who delivers it. Assume the physician has a mass of 100kg and is 0.5 m from the baby.
c. How do the forces compare?

10. Does the speed of a falling object depend on its mass? Does the speed of a satellite in orbit depend on its mass? Defend your answer.

View Full Posting Details