JHS Regents Chemistry Department



Name: _____________________________

Partner: ____________________________

JHS Regents Chemistry Department

The Determination of the Mass of a Product of a Chemical Reaction

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Introduction:

Reacting sodium bicarbonate with an aqueous solution of hydrochloric acid will produce an aqueous solution of sodium chloride, carbon dioxide, and water. Geologists use a similar reaction to test rocks for the presence of limestone (calcium carbonate). A few drops of hydrochloric acid are placed on a sample of rock. If bubbles of gas can be observed, then it is assumed that the rock contains limestone.

The reaction of sodium hydrogen carbonate with hydrochloric acid is a convenient reaction to use in studying relationships in chemical equations. A careful measurement of the mass of NaHCO3 and knowledge of the balanced equation one can calculate the mass of NaCl that will be produced.

Objective: Using grams of NaHCO3 and a balanced chemical equation to predict, and then verify the grams of NaCl produced.

|CAUTION: |

|Follow instructions exactly. Signed: __________________ |

|Handle all glassware gently Dated: __________________ |

|Handle acids carefully |

|Clean up any spills immediately and inform the teacher. |

Pre-Lab Questions:

1. Write out the balanced formula equation for the following reaction:

Solid sodium hydrogen carbonate reacts with aqueous hydrochloric acid to produce aqueous sodium chloride, carbon dioxide gas and water.

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2. According to the equation, what is the ratio of moles of sodium hydrogen carbonate to moles of sodium chloride?

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Procedure:

1. Label a 150-mL beaker with initials and lab period.

2. Place the empty 150-mL beaker on the electronic balance. Record this value in

your data table.

3. Add one scoopful (moderately heaping) of sodium bicarbonate to the beaker and

record the mass on your data table.

4. Determine the mass of sodium bicarbonate used in the experiment and record the

information on the data table.

5. Into a separate 100mL beaker pour out approximately 20 mL of 3M HCl(aq) .

Obtain a disposable dropper and place it in your beaker.

6. Add 3 drops of HCl(aq) to the NaHCO3 beaker. Observe the chemical change.

7. Continue adding the acid slowly drop by drop and carefully swirling the solution

until the reaction has completed (stop adding acid when all bubbling has ceased).

Pour the unused HCl(aq) down the sink and rinse with water.

8. Using a hot plate; heat the beaker and its contents carefully until the water is

evaporated. Allow the beaker to cool.

9. Record the mass of the beaker and its contents on your data table.

10. To make sure that all the water has evaporated off…reheat the beaker for about 3

minutes. And record the mass. If the mass has not changed you are done and

work on your calculation

Data Table:

|Mass of empty 150 mL beaker | |

|Mass of NaHCO3 & beaker | |

|Mass of NaCl & beaker (1st heating) | |

|Mass of NaCl & beaker (2nd heating) | |

|Mass of NaCl and beaker (heated to constant mass) | |

|Mass of NaCl produced (measured value) | |

Calculations: Show all work!!

1. Based on the information on your data table, calculate the masses of

a. Sodium hydrogen carbonate __________________________________

b. Sodium chloride __________________________________

2. Calculate the number of moles of

a. Sodium hydrogen carbonate

b. Sodium chloride

3. According to the balanced equation, what is the ratio of moles of sodium hydrogen carbonate to moles of sodium chloride?

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4. How does your answer to #3 compare to the results that you obtained in #2?

Actual: Mole Ratio____________________

Experiment: Mole Ratio____________________

5. Complete the following statement using your data:

In this experiment, we started with _________moles of sodium hydrogen carbonate and should have produced ________moles of sodium chloride.

6. Convert the accepted moles of sodium chloride to grams.

(accepted value) Mass of NaCl:_______grams

7. Compare your measured value (mass of NaCl) and accepted value of NaCl using the percent error formula.

8. Discuss two possible sources of error in this experiment?

Summary Questions

1. A similar reaction occurs between limestone (calcium carbonate) and hydrochloric acid.

a. Write a balanced equation for this reaction.

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b. If 3.5 grams of limestone reacted, what masses of the following would be produced? Show all work.

Calcium chloride:

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Carbon dioxide:

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Water:

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2. Methanol, CH3OH, is a clean burning fuel. It has been investigated as a possible

alternative fuel for automobiles and other combustion engines.

a. Write a balanced chemical equation for the synthesis of methanol from carbon

monoxide and hydrogen gas.

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b. How many liters of CH3OH can be produced if 246 grams of CO is available at

STP?

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