An aqueous solution that is 10.0 percent sulfuric acid (H2SO4) by mass has a density of 1.143 g/mL. Determine the molality of the solution. ( 3 significant figures)
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m = mols/kg solvent
mols = grams/molar mass.
1.143 g/mL x 1000 mL = 1143 g = mass solution
10.0% of that is H2SO4 = 1143 x 0.100 = 114.3 g is H2SO4.
mols H2SO4 = grams/molar mass = ?
mass H2O = 1143-114.3 = 1028.7
Then m = mols/kg = ?
You take care of the number of significant figures.
Arigato
To determine the molality of the solution, we need to first find the molality, which is the moles of solute per kilogram of solvent.
Step 1: Calculate the mass of the solution.
Since the density of the solution is given as 1.143 g/mL, it means that for every 1 mL of solution, the mass is 1.143 g.
Let's assume we have 100 mL of solution, so the mass of the solution would be:
Mass of solution = 100 mL * 1.143 g/mL = 114.3 g
Step 2: Determine the mass of sulfuric acid.
Since the solution is 10.0% sulfuric acid by mass, we can calculate the mass of sulfuric acid in the solution:
Mass of sulfuric acid = 10.0% * 114.3 g = 11.43 g
Step 3: Convert the mass of sulfuric acid to moles.
To convert grams to moles, we need to know the molar mass of sulfuric acid (H2SO4).
The molar mass of H2SO4 = (2 * 1.00784 g/mol) + (32.06 g/mol) + (4 * 16.00 g/mol) = 98.09 g/mol
Using this molar mass, we can calculate the moles of sulfuric acid:
Moles of sulfuric acid = 11.43 g / 98.09 g/mol = 0.1166 mol
Step 4: Calculate the molality.
Molality (m) is defined as moles of solute per kilogram of solvent.
Since we have 100 mL of solution, we can assume that 100 g of water is present (as 1 mL of water has a density of approximately 1 g/mL), so the mass of water is 100 g.
Molality = Moles of solute / Kilograms of solvent = 0.1166 mol / 0.100 kg = 1.166 mol/kg
Therefore, the molality of the 10.0% sulfuric acid solution is 1.166 mol/kg (to 3 significant figures).
To determine the molality of the solution, you need to calculate the number of moles of solute (sulfuric acid) dissolved in 1 kilogram of solvent (water). Here's how you can find the answer:
Step 1: Convert the percent composition of the sulfuric acid solution to grams of sulfuric acid:
Mass of sulfuric acid = 10.0% × total mass of solution
Assuming we have 100 grams of solution:
Mass of sulfuric acid = 10.0 g
Step 2: Calculate the number of moles of sulfuric acid using its molar mass:
Molar mass of sulfuric acid (H2SO4) = 2(1.01 g/mol of H) + 32.07 g/mol of S + 4(16.00 g/mol of O)
Molar mass of sulfuric acid = 98.09 g/mol
Number of moles of sulfuric acid = mass of sulfuric acid / molar mass
Number of moles of sulfuric acid = 10.0 g / 98.09 g/mol
Number of moles of sulfuric acid ≈ 0.102 mol (rounded to three significant figures)
Step 3: Calculate the mass of the solvent (water) in the solution.
Density = mass / volume
Rearranging the equation, mass = density × volume
Since the density of the solution is given as 1.143 g/mL, and assuming we have 100 mL of solution:
Mass of solvent = density × volume
Mass of solvent = 1.143 g/mL × 100 mL
Mass of solvent = 114.3 g
Step 4: Calculate the molality of the solution using the formula:
Molality (mol/kg) = moles of solute / mass of solvent (in kg)
Molality = 0.102 mol / 0.1143 kg
Molality ≈ 0.892 mol/kg (rounded to three significant figures)
Therefore, the molality of the solution is approximately 0.892 mol/kg.