Physical and analytical chemistry

In summary, the solubility of substance x in water at 20 degrees Celsius is 42g/L. To create a saturated solution containing 45g of x per liter overall, a mixture of S1 and S3 must be used. The amount of S3 needed is unknown, but can be solved for using the given information and the equation [n1L1=n2L2]. The critical assumption that must be made is that the final concentration of the solution will be 45g/L.
  • #1
rngz
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Homework Statement


at 20 degree celcius, the solubility of a solid substance x in water is 42g/L. There are 3 solutions containing x kept at this temperature: S1 contains 5.1g/L,S2 contains 39g/L, and S3 contains 57g/L.so, how to make a saturated solution containing 45g x per litre overall for every 1L of S1. how much of S2 or S3 should I add??what is the critical assumption that must be taken??


Homework Equations


[n1L1=n2L2]


The Attempt at a Solution


by using the lever rules..
 
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  • #2
Do you think that taking any mixture of S1 (5.1 g/L) and S2 (39 g/L), both with lower than 45 g/L, will ever add up to 45 g/L without doing something like boiling off or removing some of the liquid?

If not, then that means it must be some mixture of S1 and S3. How much S3? We don't know, so call it "x". The problem says you have 1 Liter of S1. What if I told you there were x = 5 Liters of S3 (by the way, that's not the correct answer), how would you go about calculating the final concentration? Try that problem first. Use dimensions to help guide you through it.

Now, do the same calculation except set the final concentration to 45 and replace 5 Liters with "x" and do the algebra to find "x".
 
  • #3


I would first like to commend you for considering the critical assumption that must be taken into account when dealing with solubility calculations. In this case, the critical assumption is that the solubility of a substance in a solvent is directly proportional to the temperature of the solution. This means that the solubility of substance x in water at 20 degrees Celsius will remain constant regardless of the concentration of the solution.

To make a saturated solution containing 45g of x per liter overall, we can use the equation n1L1 = n2L2, where n represents the number of moles and L represents the volume of the solution. We know that the solubility of x in water at 20 degrees Celsius is 42g/L, so we can set n1 = 45g/L and n2 = 42g/L. This gives us the equation 45g/L * L1 = 42g/L * L2.

We also know that the total volume of the solution will be 1L, so we can substitute L2 = 1L - L1 into the equation to get 45g/L * L1 = 42g/L * (1L - L1). Solving for L1, we get L1 = 0.9L. This means that we need to add 0.9L of solution S1 to 0.1L of either S2 or S3 to make a saturated solution containing 45g of x per liter overall.

To determine which solution to add, we can use the lever rule. The lever rule states that the ratio of the two solutions added will be equal to the ratio of their respective solubilities. In this case, we have S1 with a solubility of 5.1g/L and either S2 or S3 with a solubility of 39g/L or 57g/L respectively. The ratio of S1 to S2 is 5.1/39 = 0.13 and the ratio of S1 to S3 is 5.1/57 = 0.09. This means that we should add 0.13L of S2 and 0.87L of S3 to make a saturated solution containing 45g of x per liter overall.

In summary, to make a saturated solution containing 45g of x per liter overall, we need to mix 0
 

1. What is the difference between physical and analytical chemistry?

Physical chemistry is the study of the physical properties and behavior of matter, including the interaction of different substances and energy. Analytical chemistry, on the other hand, focuses on the identification, quantification, and separation of substances in a sample.

2. What are some common techniques used in physical and analytical chemistry?

Some common techniques used in physical and analytical chemistry include spectroscopy, chromatography, mass spectrometry, and electrochemistry. These techniques allow scientists to analyze the composition, structure, and properties of substances.

3. How is physical and analytical chemistry used in everyday life?

Physical and analytical chemistry have various applications in everyday life, such as in the production of medicines, food and beverage testing, environmental monitoring, and development of new materials and technologies. These fields also play a crucial role in fields like forensic science and pharmaceutical research.

4. What skills are needed to be successful in physical and analytical chemistry?

Successful physical and analytical chemists possess strong analytical and problem-solving skills, as well as a solid understanding of mathematics and physics. They also need to be detail-oriented, have good laboratory skills, and be able to work with complex instrumentation and data analysis software.

5. How does physical and analytical chemistry contribute to scientific advancements?

Physical and analytical chemistry play a crucial role in scientific advancements by providing a deeper understanding of the fundamental principles of matter and its behavior. This knowledge is then applied to develop new materials, improve existing processes and technologies, and identify solutions to real-world problems in various industries and fields of research.

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