a solution of 30% ethanol by weight has a density of 0.96g/ml at 25 degree celsius. find the molarity.
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assume you have 1000ml of the stuff.
Then mass=.96*1000=960grams.
But 30 percent is ethanol, so
ethanol mass=288grams.
change that mass to moles (divide by mol mass of ethanol)
Molarity=molesEthanol/volumesolution=molesEthanol/1
To find the molarity of the solution, we will first need to find the moles of ethanol present in 1 liter (1000 ml) of the solution.
Step 1: Convert the density from g/ml to g/L.
Since the solution has a density of 0.96 g/ml, we can multiply this by 1000 to convert it to g/L.
Density (g/L) = 0.96 g/ml × 1000 ml/L = 960 g/L
Step 2: Calculate the mass of ethanol present in 1 liter of the solution.
In a 30% ethanol solution, 30% of the solution's mass is ethanol.
Mass of ethanol (g) = 30% × 960 g/L = 0.30 × 960 g/L = 288 g/L
Step 3: Calculate the molar mass of ethanol.
The molar mass of ethanol (C2H5OH) can be found by adding up the atomic masses of its constituent elements.
Molar mass of ethanol (C2H5OH) = 2 × atomic mass of carbon (C) + 6 × atomic mass of hydrogen (H) + atomic mass of oxygen (O)
= 2 × 12.01 g/mol + 6 × 1.01 g/mol + 16.00 g/mol
≈ 46.07 g/mol
Step 4: Calculate the number of moles of ethanol.
Number of moles of ethanol (mol) = Mass of ethanol (g) / Molar mass of ethanol (g/mol)
= 288 g/L / 46.07 g/mol
Step 5: Convert the number of moles to molarity.
Molarity (M) = Number of moles of solute (ethanol) / Volume of solvent (L)
= Number of moles of ethanol (mol) / Volume of solution (L)
= (288 g/L / 46.07 g/mol) / 1 L
So, the molarity of the 30% ethanol solution is (288 g/L / 46.07 g/mol) / 1 L.