Imagine That You Work At A Company That Prepares Chemicals

1imagine That You Work At A Company That Prepares Chemical Solutions

Imagine that you work at a company that prepares chemical solutions. You are asked to label a solution to sell to different customers. One customer is a hospital, another is a chemistry lab at a university, and a third is a physics lab at a university. You added 900 kg of NaCl in a 100-liter container and filled it with water to a volume of 100 liters. Assume standard (STP) conditions. Determine the following:

• Mass percentage of the solution for the customer in the hospital
• Molarity for the customer in the chemistry lab
• Molality for the customer of the physics lab

A researcher is often required to prepare solutions in the lab. Typically, a lab provides a concentrated solution. This solution must be diluted to the proper concentration. Hydrochloric acid is a common stock solution that is typically purchased at 37.0% HCl concentration (density = 1.20 g/ml). You must make 100 ml of 0.25 M HCl to do a DNA extraction experiment. How much of the 37.0% HCl concentration stock do you need to prepare this solution?

The Haber–Bosch process for fixation of nitrogen is one of the more important chemical reactions ever invented. Without the invention of this process, which is used to make ammonia for fertilizer, the world’s population would not be as large as it is today. The reaction is:

N₂ (g) + 3H₂ (g) → 2NH₃ (g)

• List three ways in which the yield of ammonia in the reaction above can be improved for a given amount of H₂.
• Additionally, explain the principle behind each method.

Paper For Above instruction

Preparing chemical solutions requires precise calculations tailored to the needs of different clients or experiments. This paper discusses how to determine key concentration metrics for solutions and explores methods to optimize the yield of ammonia in the Haber-Bosch process, an essential industrial reaction.

Part 1: Solution Labeling for Different Customers

In a scenario where a company prepares solutions for diverse customers, accurate characterization of the solution is essential. Here, a solution containing 900 kg of NaCl dissolved in water is considered for three different settings: a hospital, a university chemistry laboratory, and a university physics laboratory. The key parameters to determine involve the mass percentage, molarity, and molality, respectively.

Mass Percentage for the Hospital Customer

Mass percentage (w/w%) is defined as the mass of solute divided by the total mass of solution, multiplied by 100. To compute this, the total mass of the solution must be determined. The 900 kg of NaCl is the solute, and the solvent (water) volume is given as 100 liters.

Using the density of water (approximately 1 kg per liter), 100 liters of water weigh roughly 100 kg. Therefore, the total mass of the solution:

Total mass = mass of NaCl + mass of water = 900 kg + 100 kg = 1000 kg.

The mass percentage:

Mass percentage = (900 kg / 1000 kg) × 100 = 90%.

This indicates that the solution is 90% NaCl by mass, suitable for labeling for the hospital customer, especially if a high-concentration solution is needed for procedures like saline infusion or cleaning.

Molarity for the Chemistry Lab Customer

Molarity (M) is moles of solute per liter of solution. To find molarity, determine the number of moles of NaCl in the solution and the volume of the solution in liters.

Molecular weight of NaCl = 58.44 g/mol. The total mass of NaCl is 900 kg = 900,000 g. The number of moles:

Number of moles = 900,000 g / 58.44 g/mol ≈ 15,395 mol.

The volume of the solution is given as 100 liters, so the molarity is:

Molarity = 15,395 mol / 100 L ≈ 153.95 M.

This extremely high molarity indicates a highly concentrated solution, which may be used as a stock solution for preparing more dilute solutions in chemical research.

Molality for the Physics Lab Customer

Molality (m) is moles of solute per kilogram of solvent. To compute this, the solvent's mass must be accurately known. The solvent water has a mass of approximately 100 kg, as 100 liters of water weigh about 100 kg.

The moles of NaCl are still 15,395 mol, so molality:

Molality = 15,395 mol / 100 kg = 153.95 mol/kg.

Thus, the molality of the solution for the physics lab is roughly 154 mol/kg, representing a very concentrated solution suitable for experiments requiring high ionic strength or concentration.

Part 2: Dilution from a Concentrated Hydrochloric Acid Stock Solution

Given a stock solution of 37.0% HCl with a density of 1.20 g/mL, the goal is to prepare 100 mL of 0.25 M HCl solution for DNA extraction experiments.

The first step involves calculating the amount of HCl in grams present in 100 mL of the stock solution. The mass of the stock solution:

Mass = volume × density = 100 mL × 1.20 g/mL = 120 g.

The amount of pure HCl in this stock:

Mass of HCl = 37.0% of 120 g = 0.37 × 120 g = 44.4 g.

The molar mass of HCl is approximately 36.46 g/mol. The number of moles in the stock is:

44.4 g / 36.46 g/mol ≈ 1.218 mol.

To prepare 0.25 M solution at 100 mL (0.1 L), the required moles are:

0.25 mol/L × 0.1 L = 0.025 mol.

Calculate the volume of stock needed to get 0.025 mol of HCl:

Volume of stock = 0.025 mol / (1.218 mol / 100 mL) ≈ 2.05 mL.

Therefore, approximately 2.05 mL of the 37% HCl stock solution should be diluted with water to reach a total volume of 100 mL, producing the desired concentration.

Part 3: Improving Ammonia Yield in the Haber–Bosch Process

The Haber–Bosch process synthesizes ammonia from nitrogen and hydrogen gases. Enhancing the efficiency of this reaction is vital for industrial productivity. Three common methods to improve ammonia yield include increasing pressure, elevating temperature, and adding catalysts.

1. Increasing Pressure

By increasing the system's pressure, the equilibrium shifts toward the production of ammonia, according to Le Châtelier's principle, which states that the system responds to a change in conditions by shifting the equilibrium to counteract the change. Since the reaction results in fewer moles of gas (from 4 moles to 2 moles), higher pressure favors ammonia formation, increasing yield.

2. Elevating Temperature with Catalyst Use

Although higher temperatures tend to favor the forward reaction's kinetic rate, they shift the equilibrium toward reactants. Therefore, a compromise involves operating at elevated temperatures with effective catalysts (like iron catalysts with promoters), which lower activation energy, enhance reaction rate, and allow higher yields at economically feasible conditions.

3. Catalyst Facilitation and Optimization

The use of catalysts accelerates the reaction rate and can also shift equilibrium favorably if selectivity enhances ammonia formation. Catalyst promoters such as potassium and aluminum oxides improve iron catalyst efficiency, leading to higher ammonia yields without excessively high temperatures or pressures.

Conclusion

Optimizing the Haber–Bosch process involves a complex interplay of pressure, temperature, and catalysts. Increasing pressure favors ammonia formation due to Le Châtelier's principle, while the use of catalysts allows higher reaction rates at lower temperatures, improving overall yield. These improvements are foundational in chemical manufacturing, enabling large-scale production essential for global agriculture and population sustenance.

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