Question

1.) How much ethanol, C2H5OH, in liters (d=0.789g/ml) must be dissolved in water to produce 190.5 of 1.65 M C2H5OH? (Molarity problem.)


2.) How much concentrated hydrochloric acid solution (36.0% HCl by mass, d = 1.18g/mL}), in milliliters, is required to produce 11.0 L of 0.296 M HCl?

Answer 1

1.) How much ethanol, C2H5OH, in liters (d=0.789g/ml) must be dissolved in water to produce 190.5 of 1.65 M C2H5OH? (Molarity problem.)
<b>
190.5 WHAT for crying out loud?barrels, freight cars, lakes, I will assume you meant mL. If not that, adjust values below to what you should have written.
M = moles/L and moles = grams/molar mass.

1.65M = moles/0.1905. Calculate moles.
moles = gram/molar mass.
You know moles and molar mass, calculate grams.
From the density, calculate volume of ethanol to use and convert to liters.</b>

Answer 2

molarity=mass/molmass*volumeinLiters

1) massEthanol=density*volumeEthanol

so volumeEthanol=molarity*molmass*Volumesolution/density

Watch units.

2)work out the similar steps for the HCL.

Answer 3

2.) How much concentrated hydrochloric acid solution (36.0% HCl by mass, d = 1.18g/mL}), in milliliters, is required to produce 11.0 L of 0.296 M HCl?
<b>
First calculate the molarity of the concentrated HCl.
1.18 g/mL x 1000 mL - mass of 1 L = 1180 g.
How much of that is HCl? 36% so,
1180 x 0.36 = 424.8 g HCl.
How many moles is that?
424.8/36.5 = 11.6 M
Now use the dilution formula to determine what you want to prepare.
mL x M = mL x M
Check my work. I estimated the molar masses and rounded here and there so you need to go through the problem yourself and do those numbers right. </b>

Answer 4

The second one is correct. Regarding the first one though, I calculated the grams to 6.8 g of C2H5OH. I don't quite understand the next step (regarding the density, etc)

Answer 5

that was me who posted the comment above. my friend had the same question.

Answer 6

I don't know how you obtained 6.8 g.
The part about the density:
The problem asks for VOLUME of ethanol to add to make ?? soln of ??M.
mass = volume x density
You calculate mass from above, substitute density here of 0.789, and solve for volume (in mL). Then convert to L. Look at your math. I don't get 6.18 grams (more like 15 g or so--in round numbers).