Respuesta :

the molar mass of Na₂SO₄ - 
2 x Na - 2 x23 = 46
1 x S - 1 x 32 = 32 
4 x O - 4 x 16 = 64 
total = 46 + 32 + 64 = 142 g/mol
the molarity of solution - 2.0 M 
in 1 L of solution , 2.0 moles
Therefore in 2.5 L - 2 mol/L x 2.5 L = 5 mol
then the mass of Na₂SO₄ required = 142 g/mol x 5 mol = 710 g
oladayoademosu

The mass of Na₂SO₄ needed to make 2.5L of 2.0M solution is 710 g.

Since we have 2.5 L of 2.0 M solution of Na₂SO₄, we determine the number of moles of Na₂SO₄ present in the solution, n.

So, number of moles, n = MV where

  • M = molarity of solution = 2.0 M and
  • V = volume of solution = 2.5 L

So, substituting the values of the variables into the equation, we have

n = MV

= 2.0 M × 2.5 L

= 5.0 mol

Also, we know that number of moles, n = m/M where

  • m = mass of Na₂SO₄ and
  • M = molar mass of Na₂SO₄.

M = 2 × molar mass Na + molar mass S + 4 × molar mass O

= 2 × 23 g + 32 g + 4 × 16 g

= 46 g + 32 g + 64 g

= 142 g/mol

So, making m subject of the formula,

m = nM

Substituting the values of the variables into the equation, we have

m = 5.0 mol × 142 g/mol

m = 710 g

So, the mass of Na₂SO₄ needed to make 2.5L of 2.0M solution is 710 g.

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