Question

100 ml of ethyl alcohol is made up to a litre of with distilled water if the

density of c2h5oh is 0.46g/ml then molality is

Answer 1

Density of ethyl alcohol = mass / volume
Hence,
mass = density * volume
mass = 0.789 g/mL * 200 mL
mass = 157.8 g

Note: volume of solution in above case = 100mL + 100 mL = 200 mL

We know,
Number of moles of ethyl alcohol ( n ) = mass / molecular mass
n = 157.8 / 46
n = 3.43 mol

Note: molecular mass of C2H5OH = 2*12 + 5*1 + 16*1 + 1 = 46 g

Molarity of ethyl alcohol ( M ) = number of moles of ethyl alcohol / total volume (in Litres)
M = 3.43/ 0.2
M = 17.15 g/L

Note: In molarity volume should always be in Litres. Hence, above, Volume = (100 + 100) mL = 200 mL = (200/1000) L = 0.2 L.

Answer 2

Explanation:

the answer is in above photo