CH 151 Lab 4 -Saddam Hossain

.pdf

School

CUNY Queensborough Community College**We aren't endorsed by this school

Course

CH 151

Subject

Chemistry

Date

Dec 18, 2024

Pages

Uploaded by AmbassadorAtomLobster14

Name: Saddam Hossain General Chemistry 1Partners Name: Prof: Dr. Sujun Wei Lab Report 1. Fahmida Hoque 2. Daiana yosopov Title: Composition of a Mixture Objectives:To determine the composition of an unknown mixture by separating and identifying its components and to calculate the mass percentage of each component in the mixture. Introduction: Mixtures are physical combinations of two or more substances that retain their individual chemical properties. This experiment aimed to separate and analyze an unknown mixture to determine its composition. The separation was based on the different thermal properties of the components. Sodium bicarbonate (NaHCO₃) decomposes upon heating, releasing carbon dioxide (CO₂) and water vapor (H₂O). By measuring the mass lost due to decomposition, the mass of NaHCO₃ in the mixture can be calculated. The remaining component, assumed to be sodium chloride (NaCl), is then identified by calculation based on the total mass of the mixture.

Material:Balance (accurate to 0.001 g) Bunsen burner or hot plate Crucible with cover Tongs Desiccator (optional) Unknown mixture (sample number 6) Heat-resistant gloves Safety goggles Chemical Used:Sodium bicarbonate (NaHCO₃) (expected component) Sodium chloride (NaCl) (expected component)

Procedure 1.Record the mass of the clean, dry crucible and cover together. 2.Weigh a known amount of the unknown mixture and add it to the crucible. Record the combined mass of the crucible, cover, and mixture. 3.Heat the crucible gently with a Bunsen burner or hot plate for a few minutes. Allow the crucible to cool slightly between heating cycles. 4.After heating, place the crucible and cover in a desiccator (if available) for 5-10 minutes to cool completely and prevent moisture absorption. 5.Weigh the cooled crucible, cover, and residue. Repeat steps 3-5 until a constant mass is achieved, indicating complete decomposition of NaHCO₃.6.Calculate the mass of the unknown mixture by subtracting the initial mass of the crucible and cover from the combined mass. 7.Calculate the mass loss due to decomposition by subtracting the final mass (after constant weight is achieved) from the combined mass of the crucible, cover, and initial mixture. 8.Use the mass loss and the known decomposition reaction of NaHCO₃ to calculate the mass of NaHCO₃ in the mixture (refer to calculations section).9.Calculate the mass percentage of NaHCO₃ and NaCl in the mixture (refer to calculations section).Observations:During heating, a gas evolved from the mixture, indicating decomposition. The mass of the crucible and residue decreased after each heating cycle until a constant mass was reached.

Data and Calculation:

Sources of error: 1.Inaccurate weighing of the mixture or crucible could lead to errors in the final calculations. 2.Incomplete decomposition of NaHCO₃ during heating could result in underestimation of its mass. 3.Moisture absorption by the sample after heating could cause an overestimation of the mass loss. 4.Presence of other volatile components in the mixture could affect the mass loss calculation.

Conclusion: The experiment successfully separated and identified the components of the unknown mixture (sample number 6) as NaHCO₃ and NaCl. The mass percentage of NaHCO₃ in the mixture was determined to be 45.31%, and the mass percentage of NaCl was 54.69%. The calculated percent error (5.9 Pre-Lab Questions: Experiment 4 Question 1 Part a: What is the mass of Component A?Mass of beaker + mixture = 63.95 g Mass of beaker + remaining solid (after sublimation) = 63.78 g Mass of Component A = (Mass of beaker + mixture) - (Mass of beaker + remaining solid) Mass of Component A = 63.95 g - 63.78 g = 0.17 g Part b: Calculate the mass percent of component A in the original mixture.Mass percent of Component A = (Mass of Component A / Mass of original mixture) * 100% Mass percent of Component A = (0.17 g / 1.42 g) * 100% ≈ 11.97%

Question 2 Part a: What is the mass of Component B?Mass of beaker + filtrate = 97.25 g Mass of empty beaker = 96.47 g Mass of Component B = (Mass of beaker + filtrate) - Mass of empty beaker Mass of Component B = 97.25 g - 96.47 g = 0.78 g Part b: Calculate the mass percent of component B in the original mixture.Mass percent of Component B = (Mass of Component B / Mass of original mixture) * 100% Mass percent of Component B = (0.78 g / 1.42 g) * 100% ≈ 54.93%