CHM 151 : General Chemistry 1: Conservation of Mass: Lab Assignment

Experiment 2: Compare the mass before and after the reaction. Calculate the percent deviation between the initial mass and the mass measured after the reaction.

% deviation: 0% % deviation=(mass before the reaction−mass after the reaction)/mass before the reaction×100=(41.035−41.035)/41.035×100=0

Experiment 1: Compare the masses before and after the reaction. Calculate the percent deviation between the initial mass and the mass measured after the reaction.

% deviation: 0% % deviation=(mass before the reaction−mass after the reaction)/mass before the reaction×100=(92.832−93.832)/92.832 ×100=0

Experiment 1: What can be said about the mass of the 1.0 M HCl and 1.0 M NaOH solutions after they were combined? The combined mass of the 1 M HCl and 1 M NaOH solution was lower than the sum of their individual masses. The combined mass of the 1 M HCl and 1 M NaOH solution was higher than the sum of their individual masses. The combined mass of the 1 M HCl and 1 M NaOH solution was equal to the sum of their individual masses. The combined mass of the 1 M HCl and 1 M NaOH solution could not be determined from the experiment.

The combined mass of the 1 M HCl and 1 M NaOH solution was equal to the sum of their individual masses.

Experiment 2: What could account for the change in mass that you observed after opening the flask at the end of the reaction between hydrochloric acid and sodium carbonate? More air entered the flask causing an increase in the mass. The gas produced in the reaction escaped the flask causing an increase in mass. The gas produced in the reaction escaped the flask, resulting in a decrease in mass. Some of the solution spilled causing a decrease in mass.

The gas produced in the reaction escaped the flask, resulting in a decrease in mass.

Experiment 2: Calculate the mass of the gas formed in the reaction between hydrochloric acid and sodium carbonate.

0.104 g 𝑚=𝑚flask after reaction−𝑚flask after gas released=135.035 g−134.931 g=0.104 g

Experiment 2: What was the pressure inside the Erlenmeyer flask after you opened it? 2.942 atm 0.751 atm 1.390 atm 1.000 atm

1.000 atm

Experiment 2: What was the pressure in the Erlenmeyer flask after the addition of the sodium carbonate to the hydrochloric acid? Select the closest answer. 2.931 atm 1.401 atm 1.121 atm 1.000 atm

1.401 atm

Experiment 2: What was the mass of the closed Erlenmeyer flask with the hydrochloric acid and sodium carbonate? Select the closest answer. 2.000 g 109.545 g 135.035 g 88.000 g

135.035 g

What was the mass of the 150-mL Erlenmeyer flask with the hydrochloric acid? Select the closest answer. 139.061 g 139.883 g 88.000 g 189.194 g

139.883 g In Experiment 1, the procedure calls for adding 45 mL of 1.0 M HCl into the 150-mL Erlenmeyer flask. The mass of the empty flask is 94.000 g. The total mass of the flask and 45.0 mL of 1.0 M HCl is measured as 139.883 g.

A student performs an experiment similar to Experiment 1 using hydrochloric acid (HCl) and potassium hydroxide (KOH). The mass of the hydrochloric acid solution is 250.000 g. After combining the HCl and KOH solutions, the final combined mass is 400.000 g. Given what you have learned about the conservation of mass in this experiment, what is the mass of the KOH solution? 400.000 g 250.000 g 200.000 g 150.000 g

150.000 g

Suppose a student reacted calcium carbonate with hydrochloric acid in a closed Erlenmeyer flask. One of the products is carbon dioxide gas. Use the data in the table to calculate the grams of gas produced in the reaction? Mass of empty Erlenmeyer flask 54.120 g Mass of calcium carbonate 10.000 g Mass of HCl solution 55.675 g Mass of Erlenmeyer flask + solution after reaction 115.394 g

4.401 g

Experiment 2: Calculate the mass of the contents of the flask after the reaction.

41.053g 𝑚=𝑚flask after reaction−𝑚flask=135.035 g−94.000 g=41.035 g

Experiment 2: Calculate the combined mass of the reactants, hydrochloric acid and sodium carbonate, before the reaction.

41.053g 𝑚reactants=(𝑚flask+HCl−𝑚flask)+𝑚sodium carbonate=(134.785 g−94.000 g)+0.250 g=41.035 g

Experiment 1: What was the mass of the hydrochloric acid solution added to the Erlenmeyer flask? Select the closest answer. 45.883 g 51.061 g 88.000 g 138.133 g

45.883 g

Conclusions: Suppose a student performed a precipitation reaction and then removed his precipitate. Given the data in the table, what was the mass of the reactants before the reaction? Assume no mass loss during the isolation of the precipitate. mass of empty flask 54.275 g mass of precipitate 1.240 g mass of flask and remaining contents after isolating precipitate 122.488 g

69.453 mass of the reactants before the reaction: 69.453g 𝑚reactants=𝑚flask after reaction+𝑚precipitate−𝑚flask=122.488 g+1.240 g−54.275 g=69.453 g

Experiment 1: Calculate the combined mass of the contents of the flask after the reaction.

92.832 𝑚=(𝑚flask after reaction−𝑚flask)=186.832 g−94.000 g=92.832 g

Experiment 1: Calculate the combined mass of the two reactants: hydrochloric acid and sodium hydroxide.

92.832 𝑚reactants=(𝑚flask+HCl−𝑚flask)+(𝑚flask+NaOH−𝑚flask)=(139.883 g−94.000 g)+(140.949 g−94.000 g)=92.832 g

Experiment 1: What was the mass of the empty, open 150-mL Erlenmeyer flask? Note: The sizes of containers in the lab may vary. Select the closest answer. 185.000 g 94.000 g 34.000 g 50.000 g

94.000 g In Experiment 1, the first part of the experimental procedure calls for taking a 150-mL Erlenmeyer flask from the Containers shelf and weighing it on the balance. The balance reads 94.000 g.

Conclusions: What is the gas formed in the hydrochloric acid and sodium carbonate reaction?

CO2 Carbon dioxide is formed in the reaction.

Who was the scientist that developed the law of conservation of mass? Avogadro Rutherford Dalton Lavoisier

Lavoisier

Experiment 2: What happened to the pressure inside the Erlenmeyer flask, as compared to normal atmospheric pressure, after the addition of sodium carbonate to the hydrochloric acid solution? The pressure increased. The pressure started fluctuating. The pressure did not change. The pressure decreased.

The pressure increased.

Zinc reacts with hydrochloric acid resulting in the formation of zinc chloride and hydrogen gas. What do you expect will happen to the pressure inside the reaction flask if it is closed with a rubber stopper before the reaction? The pressure will decrease. The pressure will increase. The pressure will change randomly. The pressure will not change.

The pressure will increase.

Experiment 2: What could account for the change in pressure inside the flask that you observed after the addition of the sodium carbonate to the hydrochloric acid solution? The reaction between hydrochloric acid and sodium carbonate was exothermic and caused the pressure to decrease. The fluctuations in room pressure caused an increase in the pressure inside the flask. The reaction between hydrochloric acid and sodium carbonate used some of the air trapped inside the closed flask. The reaction between hydrochloric acid and sodium carbonate produced a gas that was trapped inside the closed flask.

The reaction between hydrochloric acid and sodium carbonate produced a gas that was trapped inside the closed flask.

Conclusions: Why does the flask have to be closed during the hydrochloric acid and sodium carbonate reaction?

The reaction between hydrochloric acid and sodium carbonate produces a gas. To conserve the mass, the gas has to be trapped inside the flask.

Experiment 1: What did you observe when you combined the sodium hydroxide and hydrochloric acid solutions? Nothing happened, because sodium hydroxide does not react with hydrochloric acid. The solution turned pink because a salt was formed. The temperature increased, but no other visible signs were observed. The solution started bubbling because a gas was formed.

The temperature increased, but no other visible signs were observed.

Experiment 2: What did you observe after adding the sodium carbonate to the hydrochloric acid? There was bubbling in the Erlenmeyer flask. There was no observable change after the addition of sodium carbonate. There was a precipitation reaction in the Erlenmeyer flask. There was a color change from white to blue.

There was bubbling in the Erlenmeyer flask.

Conclusions: The law of conservation of mass states that matter is neither created nor destroyed in a chemical reaction. How do you explain iron nails getting heavier as they rust?

When rusting, the iron in the nails reacts with oxygen in the air, and therefore the mass increases.

Experiment 2: According to the law of conservation of mass, matter cannot be created nor destroyed. Do your results from this experiment agree with this law?

Yes, the results agree with the law of conservation of mass because the mass is the same before and after the reaction when the flask is closed.

Experiment 1: According to the law of conservation of mass, matter cannot be created nor destroyed. Do your results from this experiment agree with this law?

Yes, the results agree with the law of conservation of mass because the mass is the same before and after the reaction.

Conclusions: Acid-base reactions are hard to observe because they usually do not provide any visual cues. In this lab, you used a thermometer to determine that a reaction occurred between hydrochloric acid and sodium hydroxide. How could you detect the changes caused by this reaction in a classroom laboratory if you did not have access to a thermometer?

You can touch the flask and see if the flask warms up during the reaction.

Experiment 2: Record your lab results in the table. mass of empty Erlenmeyer flask (g) mass of flask + 40 mL40 mL of 1.0 M1.0 M hydrochloric acid (g) mass of flask, hydrochloric acid, and sodium carbonate right after mixing (g) mass of flask plus contents after the reaction (g) mass of flask plus contents after releasing gas (g) pressure inside the closed flask after the reaction (atm) pressure inside the flask after stopper removed and replaced (atm)

mass of empty Erlenmeyer flask (g)94.000 mass of flask + 40 mL40 mL of 1.0 M1.0 M hydrochloric acid (g)134.785 mass of flask, hydrochloric acid, and sodium carbonate right after mixing (g)135.035 mass of flask plus contents after the reaction (g)135.035 mass of flask plus contents after releasing gas (g)134.931 pressure inside the closed flask after the reaction (atm)1.401 pressure inside the flask after stopper removed and replaced (atm)1.000

Experiment 1: Record your lab results in the table. mass of first empty Erlenmeyer flask (g) mass of flask with 45 mL45 mL of 1.0 M HCl1.0 M HCl (g) mass of second empty Erlenmeyer flask (g) mass of flask with 45 mL45 mL of 1.0 M NaOH1.0 M NaOH (g) mass of flask after mixing the NaOHNaOH with HClHCl (g) mass of flask after the reaction (g) temperature of the solution before mixing (°C) temperature of the solution after mixing (°C)

mass of first empty Erlenmeyer flask (g) 94.000 mass of flask with 45 mL45 mL of 1.0 M HCl1.0 M HCl (g) 139.883 mass of second empty Erlenmeyer flask (g) 94.000 mass of flask with 45 mL45 mL of 1.0 M NaOH1.0 M NaOH (g) 140.949 mass of flask after mixing the NaOHNaOH with HClHCl (g) 186.832 mass of flask after the reaction (g)186.832 temperature of the solution before mixing (°C) 21.5 temperature of the solution after mixing (°C) 26.8