Urgent Chemistry Help Needed! Solutions Inside

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Urgent Chemistry Problems Solved!

Hey guys! Need some quick chemistry help? No problem! Let's break down these problems step-by-step to get you those points. We'll tackle the first variant problems from the image and then address the two extra problems for the second variant.

Variant 1: Image Problems

Problem 1: Sulfuric Acid Solution Concentrations

Okay, so the first task involves finding the molar and equivalent concentrations of a 24.5% sulfuric acid (H2SO4) solution. We also know the density is 1.175 g/mL. Sounds intense, right? But don't worry, it's manageable!

First, let's clarify what molar and equivalent concentrations are. Molar concentration (M), or molarity, tells us how many moles of solute (in this case, H2SO4) are dissolved in one liter of solution. Equivalent concentration (N), or normality, tells us how many gram equivalent weights of solute are dissolved in one liter of solution. Basically, it accounts for the number of reactive units in a molecule.

Here’s how we can solve this step-by-step:

  1. Assume a Volume: Let’s assume we have 1 liter (1000 mL) of the solution. This makes the calculations easier.
  2. Calculate the Mass of the Solution: Using the density, we can find the mass of the solution: Mass = Density × Volume = 1.175 g/mL × 1000 mL = 1175 g.
  3. Calculate the Mass of Sulfuric Acid: Since the solution is 24.5% H2SO4, the mass of H2SO4 in the solution is: Mass of H2SO4 = 0.245 × 1175 g = 287.875 g.
  4. Calculate the Number of Moles of Sulfuric Acid: To find the number of moles, we divide the mass of H2SO4 by its molar mass (98.08 g/mol): Moles of H2SO4 = 287.875 g / 98.08 g/mol = 2.935 mol.
  5. Determine the Molar Concentration: Since we assumed 1 liter of solution, the molar concentration is simply the number of moles we just calculated: Molar Concentration (M) = 2.935 mol/L = 2.935 M.
  6. Calculate the Equivalent Concentration: For sulfuric acid (H2SO4), there are two acidic hydrogens, so its equivalent weight is half its molar mass (98.08 g/mol / 2 = 49.04 g/equivalent). Therefore, the number of equivalents is: Equivalents of H2SO4 = 287.875 g / 49.04 g/equivalent = 5.87 equivalents. The equivalent concentration is then: Equivalent Concentration (N) = 5.87 equivalents/L = 5.87 N.

So, to summarize: The molar concentration of the 24.5% sulfuric acid solution is approximately 2.935 M, and the equivalent concentration is approximately 5.87 N.

Problem 2: Mixing HCl and NaOH Solutions

Next up, we have a mixture of hydrochloric acid (HCl) and sodium hydroxide (NaOH). We need to find the pH of the resulting solution and determine if it's acidic, basic, or neutral. Let’s dive in!

Here’s the breakdown:

  1. Calculate Moles of HCl: We have 20 mL of 0.1 M HCl. So, moles of HCl = Volume (L) × Molarity = (20 mL / 1000 mL/L) × 0.1 mol/L = 0.002 mol.
  2. Calculate Moles of NaOH: We have 30 mL of 0.2 M NaOH. So, moles of NaOH = Volume (L) × Molarity = (30 mL / 1000 mL/L) × 0.2 mol/L = 0.006 mol.
  3. Determine the Limiting Reactant: HCl and NaOH react in a 1:1 molar ratio: HCl + NaOH → NaCl + H2O. Since we have 0.002 mol of HCl and 0.006 mol of NaOH, HCl is the limiting reactant. All the HCl will be consumed, and some NaOH will be left over.
  4. Calculate Excess Moles of NaOH: Moles of excess NaOH = Initial moles of NaOH - Moles of HCl = 0.006 mol - 0.002 mol = 0.004 mol.
  5. Calculate the Concentration of Excess NaOH: The total volume of the solution is 20 mL + 30 mL = 50 mL = 0.050 L. The concentration of excess NaOH is: [NaOH] = Moles of excess NaOH / Total volume = 0.004 mol / 0.050 L = 0.08 M.
  6. Calculate the pOH: Since NaOH is a strong base, it completely dissociates in water. Therefore, [OH-] = [NaOH] = 0.08 M. The pOH is: pOH = -log[OH-] = -log(0.08) = 1.097.
  7. Calculate the pH: We know that pH + pOH = 14. Therefore, pH = 14 - pOH = 14 - 1.097 = 12.903.
  8. Determine the Reaction of the Solution: Since the pH is 12.903 (which is > 7), the solution is basic (alkaline).

In summary: The pH of the solution is approximately 12.903, indicating that the solution is basic.

Variant 2: Additional Problems

Problem 3: Salt Solution

The prompt mentions a salt solution problem but doesn't provide the complete question. To properly address this problem, I need the full question text. However, I can demonstrate how to approach common salt solution problems.

Typically, these problems involve calculating the concentration of a salt solution after adding more salt or water, or after evaporation.

General Steps to Solve Salt Solution Problems:

  1. Identify the Knowns: Determine the initial mass of the solution, the initial concentration (%), the mass of salt added/removed, the mass of water added/removed, or the amount of water evaporated.
  2. Calculate the Initial Mass of Salt: Mass of salt = (Initial concentration / 100) × Initial mass of solution.
  3. Calculate the Final Mass of Salt: If salt is added, add the mass of salt added to the initial mass of salt. If salt is removed, subtract the mass of salt removed.
  4. Calculate the Final Mass of Solution: If water is added, add the mass of water added to the initial mass of the solution. If water is removed (evaporated), subtract the mass of water removed. If salt is added, add the mass of salt added to the initial mass of the solution. If salt is removed, subtract the mass of salt removed.
  5. Calculate the Final Concentration: Final concentration = (Final mass of salt / Final mass of solution) × 100.

Example (Assuming a question):

Problem: From a 400 g salt solution with a concentration of 10%, 50 g of water is evaporated. What is the concentration of the remaining solution?

Solution:

  1. Knowns: Initial mass of solution = 400 g, Initial concentration = 10%, Water evaporated = 50 g.
  2. Initial Mass of Salt: Mass of salt = (10/100) × 400 g = 40 g.
  3. Final Mass of Salt: Since no salt was added or removed, the final mass of salt is still 40 g.
  4. Final Mass of Solution: Final mass of solution = 400 g - 50 g = 350 g.
  5. Final Concentration: Final concentration = (40 g / 350 g) × 100 = 11.43%.

Therefore, the concentration of the remaining solution is 11.43%.

To give you a specific answer for your problem, please provide the complete question.

I hope this helps you understand how to solve these types of chemistry problems! Let me know if you have any other questions, and good luck with your assignment!