What is the molarity (M) of a 627 mL solution that contains 12.7 g of ethanol, CH3CH2OH?
To find the molarity (M) of a solution, you need to know the amount of solute (in moles) and the volume of the solution (in liters). Here's how you can calculate the molarity:
Step 1: Calculate the moles of ethanol:
The first step is to convert the given mass of ethanol (12.7 g) to moles. To do this, you need to know the molar mass of ethanol, which can be calculated by adding up the atomic masses of its constituent elements.
The molar mass of carbon (C) is 12.01 g/mol, the molar mass of hydrogen (H) is 1.01 g/mol, and the molar mass of oxygen (O) is 16.00 g/mol.
The molar mass of ethanol (CH₃CH₂OH) can be calculated as follows:
(2 × molar mass of carbon) + (6 × molar mass of hydrogen) + molar mass of oxygen
= (2 × 12.01 g/mol) + (6 × 1.01 g/mol) + 16.00 g/mol
= 24.02 g/mol + 6.06 g/mol + 16.00 g/mol
= 46.08 g/mol
Now, you can calculate the moles of ethanol by dividing the given mass by the molar mass:
moles = mass / molar mass
moles = 12.7 g / 46.08 g/mol
Step 2: Convert the volume of the solution to liters:
The given volume of the solution is 627 mL. To calculate the volume in liters, you need to divide by 1000 since there are 1000 mL in a liter.
volume (in liters) = 627 mL / 1000 mL/L
Step 3: Calculate the molarity:
Finally, to find the molarity, divide the moles of ethanol by the volume in liters:
Molarity (M) = moles / volume (in liters)
Now, you can substitute the values into the formula to find the molarity.