Answer:
1. 0.22 mol/dm³
2. 0.23 mol/dm³
Explanation:
Molarity: This can be defined as the concentration of a substance in mol per dm³
1.
M = n/v ...................... Equation 1
M = molarity of methanol, n = number of mole of methanol, v = volume of the solvent/water/solution.
n = g/m.m
Where g = mass of methanol, m.m = molar mass of methanol.
g = 6.4 g, m.m = 32 g /mole.
n = 6.4/32 = 0.2 mole
and ,
v = m/d
Where m = mass of water, d = density of water
m = mass of 50 moles of water = 18×50 = 900 g.
d = 1000 g/dm³.
v = 900/1000 = 0.9 dm³
Substituting the value of v and n into equation 1
M = 0.2/0.9
M = 0.22 mol/dm³
2.
M = n/v
v = volume of the solution
v = (mass of methanol + mass of water in the solution)/density of the solution
v = [(900+6.4)/1000]/1.03
v = 0.9064/1.03
v = 0.88 dm³
n = 0.2 mole
Therefore,
M = 0.2/0.88
M = 0.23 mol/dm³
