Preparing Aqueous Solutions for Chemistry Students

[jdhutto]

Chem problem need help...

Homework Statement

How would you prepare the following aqueous solutions?
(a) 1.10 kg of 0.0515 m ethanol (C2H5OH) from ethanol and water
Add___ g C2H5OH to ____ g H2O.

(b) 511 g of 15.0 mass % HCl from 35.3 mass % HCl
Add___ g of 35.3% HCl to ___ g of water.

Homework Equations

The Attempt at a Solution

Im not sure what to do here...somebody please tell me the steps

 

[rocomath]

work? attempt? effort?

 

[Blueshift5]

to get the answer

I would first look at the given information and determine the desired concentration and amount of solution needed. In part (a), the desired concentration is 0.0515 m and the desired amount is 1.10 kg. This means that we need 0.0515 moles of ethanol in 1.10 kg of solution.

To calculate the amount of ethanol needed, we can use the formula:

Amount of solute (in moles) = concentration (in moles/liter) x volume (in liters)

Since we know the desired concentration and the desired amount, we can rearrange the formula to solve for the volume of solution needed:

Volume of solution (in liters) = amount of solute (in moles) / concentration (in moles/liter)

Plugging in the values, we get:

Volume of solution = 0.0515 moles / 0.0515 moles/liter = 1 liter

Since we know that the solution is 1.10 kg, we can convert this to grams (1 kg = 1000 g) and subtract the mass of water to get the mass of ethanol needed:

Mass of ethanol = 1.10 kg - 1000 g = 100 g

Therefore, we need to add 100 g of ethanol to 1 liter of water to prepare 1.10 kg of 0.0515 m ethanol solution.

In part (b), we are given the mass percentage of HCl (35.3%) and the desired mass of solution (511 g). We can use the formula:

Mass of solute (in grams) = mass percentage x mass of solution (in grams)

to calculate the mass of HCl needed. Plugging in the values, we get:

Mass of HCl = 0.353 x 511 g = 180.383 g

Since we are given a solution with a different concentration (15.0%) and need to prepare a solution with a different concentration (35.3%), we can use the following formula:

Concentration (in mass %) = mass of solute (in grams) / mass of solution (in grams) x 100%

Rearranging this formula to solve for the mass of solution, we get:

Mass of solution = mass of solute (in grams) / concentration (in mass %) x 100%

Plugging in the