Question

Hydrated sodium carbonate has the formula Na₂CO3.10H₂O.

[1]
(a) Calculate the relative molecular mass (M₁) of Na₂CO3.10H₂0.
(22.99)2 + 12.01 + ( 16.00) 3 + 10 C (1.01) 2 +
16.00] = 105.99 + 10 (18.02)
286.19 g/mol
M₁ = 28.6.19
(b) Calculate the mass of Na₂CO3.10H₂O needed to make 250 cm³ of a 0.10 mol dm3
solution.
[1]
Mass=
g

Answer 1

Step-by-step explanation:

a) To calculate the relative molecular mass of Na2CO3.10H2O, you need to add up the relative atomic masses of each element in the formula.

Na₂CO3.10H₂O: 2(22.99) + 12.01 + 3(16.00) + 10(1.01) + 2(18.02) = 286.19 g/mol

M₁ = 286.19 g/mol

(b) To make a 250cm³ of 0.10 mol/dm³ solution, we need to calculate the number of moles of Na2CO3.10H2O, and then multiply it by the molar mass of Na2CO3.10H2O to find the mass needed.

First, we calculate the number of moles present in 250 cm³ of 0.10 mol/dm³ solution:

moles = concentration x volume = 0.10 mol/dm³ x 0.25 dm³ = 0.025 mol

Then we multiply the moles by the molar mass to find the mass needed:

mass = moles x molar mass = 0.025 mol x 286.19 g/mol = 7.15 g

So we need 7.15 g of Na2CO3.10H2O to make 250 cm³ of a 0.10 mol/dm³ solution.