You want to make up a 0,100 mol.dm^-3 sodium carbonate solution. You have a 200ml volumetric flask and a bottle of sodium carbonate decahydrate (Na2CO2 •10H2O). Calculate the mass of crystal that you need to weigh off. (5,72)
To calculate the mass of sodium carbonate decahydrate (Na2CO3 · 10H2O) needed, we need to use the molar mass and the given volume.
First, let's calculate the molar mass:
2 sodium atoms (2 Na) = 2(22.99 g/mol) = 45.98 g/mol
1 carbon atom (C) = 1(12.01 g/mol) = 12.01 g/mol
3 oxygen atoms (3 O) = 3(16.00 g/mol) = 48.00 g/mol
10 water molecules (10 H2O) = 10(2(1.01 g/mol) + 16.00 g/mol) = 10(18.02 g/mol) = 180.20 g/mol
Now, let's calculate the molar mass of sodium carbonate decahydrate:
Molar mass of Na2CO3 · 10H2O = 45.98 g/mol + 12.01 g/mol + 48.00 g/mol + 180.20 g/mol = 286.19 g/mol
To calculate the mass needed for a 0.100 mol/dm³ solution in a 200 mL volumetric flask, we can use the formula:
Mass (g) = Molar concentration (mol/dm³) × Volume (dm³) × Molar mass (g/mol)
Since the volume is given in milliliters (mL), we need to convert it to decimeters cubed (dm³):
Volume (dm³) = 200 mL ÷ 1000 mL/dm³ = 0.2 dm³
Substituting the values into the formula:
Mass (g) = 0.100 mol/dm³ × 0.2 dm³ × 286.19 g/mol = 5.722 g
Therefore, you need to weigh off approximately 5.72 grams of sodium carbonate decahydrate for the 0.100 mol/dm³ solution in the 200 mL volumetric flask.
To calculate the mass of sodium carbonate decahydrate needed for the solution, we can use the formula:
M = (m/M) / V
Where:
M = molar concentration (mol.dm^-3)
m = mass of solute (g)
M = molar mass of solute (g/mol)
V = volume of solution (dm^3)
Given:
Molar concentration (M) = 0.100 mol.dm^-3
Volume of solution (V) = 200 mL = 0.200 dm^3
First, we need to convert the volume of the solution from mL to dm^3:
V = 0.200 dm^3
Next, we need to find the molar mass of sodium carbonate decahydrate (Na2CO3 •10H2O):
Molar mass of Na2CO3 = 2(22.99 g/mol) + 12.01 g/mol + 3(16.00 g/mol) = 105.99 g/mol
Molar mass of 10H2O = 10(2(1.01 g/mol) + 16.00 g/mol) = 180.18 g/mol
Finally, we can calculate the mass of sodium carbonate decahydrate (Na2CO3 •10H2O) needed:
m = M * V * (Molar mass of Na2CO3 •10H2O)
= 0.100 * 0.200 * (105.99 g/mol + 180.18 g/mol)
m ≈ 5.72 g
Therefore, approximately 5.72 grams of sodium carbonate decahydrate should be weighed off.