Question

What is the molarity of a 27.0% (v/v) aqueous ethanol solution? the density of ethanol (c2h6o, molar mass 46.07 g/mol) is 0.790 g/ml?

Answer 1

Answer:

$M=4.63M$

Explanation:

Hello,

In this case, with the given by-volume percentage and considering the molarity as:

$M=\frac{n_{Ethanol}}{V_{solution}}$

We assume the solution having 100 mL of volume in total, thus, the volume of ethanol is 27.0 mL, therefore, the moles:

$n_{Ethanol}=27.0mL*\frac{0.790g}{1mL}*\frac{1mol}{46.07g}=0.463molEthanol$

Moreover, the volume of the solution in liters is:

$V_{solution}=100mL*\frac{1L}{1000mL} =0.1L$

Finally, the molarity is:

$M=\frac{0.463mol}{0.1L}\\ M=4.63M$

Best regards.

Answer 2

   The  molarity  of a  27%(v/v) aqueous  ethanol  solution  is 4.63 M

         calculation
convert  27%(v/v) to  fraction  = 27ml/100 ml

use  density to  convert  27ml  to grams =  27 ml  x0.79 g/ml = 21.33 g

find  the number  of moles  of C2H6O

moles = mass/molar mass of C2H6O(46.07 g/mol)

moles is therefore = 21.33 g /46.07 g/mol =0.463  moles

find the  molarity =   moles /volume in liters

volume in liter =  100 ml/1000 = 0.1 L

molarity  is therefore =  0.463 mole/0.1 L = 4.63  M