Calculate the amount of sodium acetate trihydrate needed to prepare 100 mL of 0.2M sodium acetate solution.
To calculate the amount of sodium acetate trihydrate needed to prepare a 0.2M sodium acetate solution, we need to consider the molar mass of sodium acetate and the desired concentration.
Step 1: Determine the molar mass of sodium acetate trihydrate.
The formula for sodium acetate trihydrate is NaCH3COO · 3H2O. To calculate the molar mass, we sum the atomic masses of the individual elements:
Na (sodium) = 22.99 g/mol
C (carbon) = 12.01 g/mol
H (hydrogen) = 1.01 g/mol
O (oxygen) = 16.00 g/mol
Therefore, the molar mass of sodium acetate trihydrate is:
(22.99g/mol × 1) + (12.01g/mol × 2) + (1.01g/mol × 3) + (16.00g/mol × 3) = 136.09 g/mol.
Step 2: Use the formula for molarity to calculate the amount of sodium acetate trihydrate needed.
The formula for molarity is:
Molarity (M) = moles of solute / volume of solution (in liters)
We are given:
Molarity (M) = 0.2M
Volume of solution = 100 mL = 0.1 L
Rearranging the formula to solve for moles of solute, we get:
Moles of solute = Molarity × Volume of solution
Moles of solute = 0.2M × 0.1 L = 0.02 moles.
Step 3: Convert moles of sodium acetate trihydrate to grams.
To convert moles to grams, we use the molar mass of sodium acetate trihydrate calculated earlier.
Grams of sodium acetate trihydrate = Moles of sodium acetate trihydrate × Molar mass of sodium acetate trihydrate
Grams of sodium acetate trihydrate = 0.02 moles × 136.09 g/mol = 2.7218 grams.
Therefore, you would need approximately 2.72 grams of sodium acetate trihydrate to prepare a 100 mL of 0.2M sodium acetate solution.