The molarity and the molality of a solution prepared by dissolving 2.00 g of ethanol C2H5OH with 100.0 g of water to give a final volume 102 mL are

would i just add both the grams and divide by 102 for molarity? and molalty i would just add the mass?

To calculate molarity and molality, you need to first determine the number of moles of ethanol and water in the solution.

Let's start with molarity:

1. Calculate the number of moles of ethanol:
Molar mass of ethanol (C2H5OH) = (2 * atomic mass of carbon) + (6 * atomic mass of hydrogen) + atomic mass of oxygen
= (2 * 12.01 g/mol) + (6 * 1.01 g/mol) + 16.00 g/mol
= 46.07 g/mol

Number of moles of ethanol = mass / molar mass
= 2.00 g / 46.07 g/mol

2. Calculate the number of moles of water:
Molar mass of water (H2O) = (2 * atomic mass of hydrogen) + atomic mass of oxygen
= (2 * 1.01 g/mol) + 16.00 g/mol
= 18.02 g/mol

Number of moles of water = mass / molar mass
= 100.0 g / 18.02 g/mol

3. Calculate the total number of moles:
Total moles = moles of ethanol + moles of water

Next, to calculate molarity:

Molarity (M) = moles / volume (in liters)

Since the final volume is given in milliliters, you need to convert it to liters:
Volume (L) = 102 mL / 1000 mL/L

Now, divide the total moles by the volume to get the molarity.

Moving on to molality:

Molality (m) = moles of solute / mass of solvent (in kilograms)

The moles of solute remain the same, but the mass of the solvent (water) needs to be converted to kilograms:
Mass (kg) = 100.0 g / 1000 g/kg

Now, divide the moles of ethanol by the mass of water (in kg) to get the molality.

In summary, adding the masses and dividing by the final volume will give you the concentration in terms of molarity. For molality, you would divide the moles of solute by the mass of the solvent in kilograms. Remember to convert units where necessary.