Solid Lab

Summary

This experiment explores the determination of Red 40 concentration in a solid sample using absorbance measurements. By dissolving the solid in water, the process combines dilution and dissolution to create a solution suitable for spectrophotometric analysis. Reference solutions are prepared using Kool-Aid to compare against the sample. Calculations involve finding total micrograms of Red 40 in the dissolved sample, leading to the final parts per million (ppm) concentration by relating the amount to the mass of the original solid. This approach highlights the effective integration of various analytical techniques in chemistry.

Takeaways

• 😀 The objective is to determine the parts per million (ppm) concentration of Red 40 in a solid sample.
• 😀 The experiment utilizes a known reference solution (Kool-Aid) to compare against the sample.
• 😀 The solid sample, such as a candy or cough drop, must be dissolved in water to measure absorbance.
• 😀 It is important to ensure the solution remains color transparent during the dissolving process.
• 😀 The dissolving process also acts as a dilution, affecting the sample's intensity.
• 😀 Absorbance measurements should fall within the range of reference solutions to ensure accuracy.
• 😀 Calculations for Red 40 concentration differ from standard dilution equations, using the total volume of the dissolved sample.
• 😀 Total micrograms of Red 40 are calculated using the measured concentration and the volume of the solution.
• 😀 The formula for ppm is micrograms of Red 40 divided by the grams of the original solid.
• 😀 This method effectively combines dissolving and diluting processes to determine the concentration of Red 40.

Q & A

What is the main goal of the lab described in the transcript?

The main goal is to determine the parts per million (ppm) of Red 40 in a solid sample, such as candy or cough drops, using absorbance measurements.

How is the experiment different from the previous lab that focused on liquids?

In this lab, instead of measuring a liquid directly, the solid sample must be dissolved in water before measuring its absorbance.

What reference solution is used in this experiment, and why?

Kool-Aid is used as a reference solution because its concentration of Red 40 is known, allowing for the creation of a standard curve for comparison.

What is the significance of ensuring the dissolved sample remains transparent?

The solution must be transparent so that absorbance measurements can be accurately taken, as any turbidity could interfere with the results.

How do you calculate the total micrograms of Red 40 in the sample?

The total micrograms of Red 40 are calculated by using the measured absorbance and the known concentration from the reference solutions, considering the volume of the dissolved sample.

What formula is traditionally used for dilution, and why is it not used here?

The formula C1V1 = C2V2 is typically used for dilution calculations, but here, the process involves dissolving the solid in a new volume, so a different approach is needed to account for the total amount of Red 40.

What is ppm, and how is it defined in the context of this experiment?

Ppm stands for parts per million and is defined as the micrograms of the substance of interest (Red 40) divided by the grams of the total substance (the original solid).

What challenges might arise when preparing the sample for absorbance measurement?

Challenges include ensuring complete dissolution of the solid, maintaining transparency of the solution, and ensuring the concentration falls within the range of the reference standards.

Why is it important to merge the processes of diluting and dissolving?

Merging these processes ensures that the final concentration of the dissolved sample is appropriate for accurate absorbance readings against the established standards.

What key steps are taken to ensure the accuracy of the final ppm calculation?

Key steps include accurately measuring the mass of the original solid, correctly dissolving it to form a transparent solution, and accurately determining the absorbance to calculate the total micrograms of Red 40.