Calculate the molarity and molality of a solution made by mixing equal volumes of 30% by weight of H2SO4 (density - Chemistry - Some Basic Concepts of Chemistry

Question

Calculate the molarity and molality of a solution made by mixing
equal volumes of 30% by weight of H2SO4 (density = 1 218 g/ml) and
70% by weight of H2SO4 (density = 1 610 g/ml)

veena Vasandani · Accepted Answer

Assume y ml of each solution, a and b, are
mixed

Calculate mass of solution using formula, mass =
density(d) × Volume (V)

Mass of solution a, ma = 1
218 × y = 1 218y
Mass H2SO4,
msolute a = 30% or 30×1
218y100
msolute a
= 0 3654y g
Moles H2SO4,
nsolute a = 0;3654y98or 0
003729y mol (Using formula, moles = mass, m /Molar
mass)
Mass of water, msolvent a =
mA- msolute a
msolvent a = 1 281y –
0 3654y
msolvent a= = 0 8526y g or
0 8526 X 10-3y kg

Similarly for solution B
mb = 1 610y g
msolute b = 70×1
610y100or 1 127y  g

nsolute b = 1 127y98 or 11
5y mol
msolvent b = 1 610y –
1 127y = 0 483y g or 0 483 ×
10-3y kg

When y ml of each solution is
mixed
Total volume, V = y + y = 2y ml or
2y × 10-3 L
Total moles of H2SO4,
nsolute = nsolute a +
nsolute b
nsolute= 0 003729y + 11 5y = 0 015229y
mol
Total mass of solvent in kg,
msolvent = msolvent
a + msolvent
b
msolvent = 1
3356y×10-3 kg
Molarity, M
=nsolute/V

M = 0 015229y2y×10-3

M = 7 614M
Molality, m = nsolutemsolvent in kg=0
015229y1 3356y×10-3=11 402m

Calculate the molarity and molality of a solution made by mixing equal volumes of 30% by weight of H2SO4 (density = 1 218 g/ml) and 70% by weight of H2SO4 (density = 1 610 g/ml)