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The density of Na2Co3 solution at 20Celsius is 1.019g/mL. The mass fraction w(Na2CO3) is 0.02 (2%). What's the concentration of the solution?

User Thatismatt
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1. we are given :

• that the mass fraction of Na2CO3 = 2%

meaning 2 grams of Na2Co3 was dissolved in 98g of water .

∴ total mass of solution = 100g

• Density = 1.019g/mL.

,

• Molar mass Na2CO3=105,9888 g/mol

2. Calculate volume

Density = mass /volume

∴Volume = mass/density = 100g /1.019g/mL.

= 90.66mL.

3.Calculate moles of the solution

n = mass Na2CO3/MolMass Na2Co3

= 2 g /105.9888g/mol

∴moles of Na2CO3 =0.019moles Na2CO3

4. Calculate the Molarity (concentration)of the solution

Molarity =( n/v) * 1000

= (0.019mol/(90.66/1000) L

= (0.019/90.66)*1000 ( multiply by 1000: 90.66/1000=0.09066)

=0.21M

This means that the concentration of the solution is 0.21M
User Lschlessinger
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