Chemistry Experiment 4: NaHCO3 Analysis

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the purpose of including the 'Ideal Gas Law' in the Statement of Purpose?

To outline the relationship between volume, temperature, and pressure of gases. (correct)

To present the chemical reactions that occur during experiments.

To describe the physical properties of solids in chemistry.

To emphasize the importance of temperature in gas experiments.

Which of the following should NOT be included in the observations section of the lab notebook?

The theoretical calculation of %C. (correct)

The behavior of gas evolution during the experiment.

The color change of the desiccant used last week.

The appearance of the sample initially.

Which calculation is essential when recording the data for gas evolved?

Temperature at the start of the experiment.

Total mass of the samples used.

Diameter of the buret used.

Final volume minus initial volume. (correct)

What should be the focus of the explanation of results in the report section?

The comparison of experimental %C with theoretical %C. Signup and view all the answers

Why is it necessary to pay attention to significant figures in the report?

To represent the precision of the measurements accurately. Signup and view all the answers

What is the source of CO2 produced in the reaction between NaHCO3 and H2SO4?

It comes from the decomposition of H2CO3. Signup and view all the answers

In the context of this experiment, what does the Ideal Gas Law (PV = nRT) help determine?

The moles of CO2 evolved. Signup and view all the answers

How is the pressure of CO2 (PCO2) calculated in this experiment?

PCO2 = Total pressure – Water vapor pressure Signup and view all the answers

What is the mole ratio between CO2 produced and C in the reaction?

1:1 Signup and view all the answers

What can be inferred about the %C in a pure sample of NaHCO3?

It remains constant regardless of sample purity. Signup and view all the answers

How is the volume of CO2 (VCO2) determined during this experiment?

By observing the displacement of water in the buret. Signup and view all the answers

What is a key factor when calculating %C in NaHCO3 from experimental data?

The amount of CO2 collected. Signup and view all the answers

What assumption does the calculation of %C rely on regarding the reaction of NaHCO3?

All C in NaHCO3 is converted into CO2. Signup and view all the answers

Study Notes

Experiment 4 Overview

Experiment 4 involves the analysis of sodium hydrogen carbonate (NaHCO3) by gas evolution.
The experiment utilizes the Ideal Gas Law (PV = nRT) and Dalton's Law to determine the percentage of carbon (%C) in the sample.
The reaction involves reacting NaHCO3 with sulfuric acid (H2SO4) to produce carbon dioxide (CO2) gas.

Reaction Equation and Decomposition

The reaction equation is: NaHCO3(s) + H2SO4(aq) ➞ H2O(l) + CO2(g) + NaHSO4(aq)
The HCO3– ion is amphoteric, meaning it can act as both an acid and a base.
CO2 evolves from the decomposition of carbonic acid (H2CO3) formed in the reaction.

Determining % Carbon

The Ideal Gas Law (PV = nRT) is used to calculate the moles of CO2 (n).
Dalton's Law (Ptotal = PCO2 + PH2O) is used to calculate the partial pressure of CO2 (PCO2).
The pressure of CO2 is calculated by subtracting the water vapor pressure (Water VP) from the atmospheric pressure (Atm P).
The temperature (T) of CO2 is the temperature of the water bath.
The volume (V) of CO2 is determined by measuring the volume of water displaced by the gas in a Mohr buret.

Calculating %C

The definition of %C is used to calculate the percentage of carbon in the sample.
The mole ratio between reactants and products is 1:1.
All carbon in NaHCO3 is converted to CO2: 1 mol CO2 = 1 mol C = 12.01 g C
To calculate %C, work backwards:
- g C is calculated from mol C.
- mol C is determined from mol CO2.
- mol CO2 is calculated using the Ideal Gas Law.

Determining % Purity

%C in a pure sample of NaHCO3 is always the same.
The % purity is determined by comparing the actual %C in the sample with the theoretical %C for pure NaHCO3.
For pure NaHCO3: %Na + %H + %C + %O = 100%
The %C for one mole of NaHCO3 is calculated as: %C = [g C/g NaHCO3] x 100%

Lab Notebook Requirements

The lab notebook should include:
- Statement of Purpose: Complete sentences describing the experiment, including the use of the Ideal Gas Law.
- Procedure: Refer to the apparatus diagram or draw it yourself.
- Observations:
  - Appearance of the sample initially (dry, white, etc.).
  - Desiccant color from the previous week (blue, pink, purple, etc.).
  - Mass of water lost.
  - Gas evolution (slowly, vigorously, etc.).
  - Water level changes in the buret.
  - Volume of gas evolved.
- Data recorded: Pressure (+0.1 mm Hg), Volume (+0.1 mL), Temperature (+0.1 °C).

Report Requirements

The report should include:
- A filled-in Report Sheet with calculations using formulas and unit labels.
- Conclusion (3rd person, past tense, passive voice):
  - Brief overview of the procedure with the reaction equation.
  - Explicitly stated results for %C and % purity.
  - Explanation of results:
    - Compare experimental %C with theoretical %C.
    - Explain why the sample is not 100% pure.
    - Discuss the precision of the results (standard deviation).

Experiment 5 Preparation

Experiment 5 will have prelab questions, extra questions, and require preparation of data tables.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers the analysis of sodium hydrogen carbonate (NaHCO3) via gas evolution, including the use of the Ideal Gas Law and Dalton's Law. You will explore the reaction involving NaHCO3 and sulfuric acid and determine the percentage of carbon from evolved CO2. Gain insights into the chemistry of carbonic acid and the principles behind gas laws.