Calculate the mass of sodium sulfate decahydrate need to make a 500ml solution that is .025m in sulfate anion?
You typed a small m which means molality. If you want M (molarity) this problem can be worked; if you want m you need the density of the solution.
To calculate the mass of sodium sulfate decahydrate (Na2SO4·10H2O) needed to make a 500 mL solution that is 0.025 M in sulfate anion (SO4^-2), you need to follow a step-by-step approach:
Step 1: Determine the molar mass of sulfate anion (SO4^-2).
The molar mass of sulfur (S) is 32.07 g/mol, and the molar mass of four oxygen (O) atoms is 16.00 g/mol each. Adding these together gives:
Molar mass of SO4^-2 = (32.07 g/mol) + (4 * 16.00 g/mol) = 96.07 g/mol
Step 2: Calculate the number of moles of sulfate anion (SO4^-2) needed.
Given that the solution's concentration is 0.025 M and the volume is 500 mL, you can use the formula:
moles = concentration (M) * volume (L)
Converting the volume to liters:
Volume = 500 mL ÷ 1000 mL/L = 0.5 L
Calculating the number of moles:
moles of SO4^-2 = 0.025 M * 0.5 L = 0.0125 moles
Step 3: Determine the number of moles of Na2SO4 (sodium sulfate) needed.
In the balanced chemical equation for sodium sulfate, each mole of Na2SO4 yields one mole of sulfate anion. Therefore, the number of moles of Na2SO4 is equal to the number of moles of sulfate anion:
moles of Na2SO4 = 0.0125 moles
Step 4: Calculate the mass of Na2SO4·10H2O needed.
The molar mass of Na2SO4·10H2O is the sum of the molar masses of its individual components:
- Molar mass of Na2SO4 = (2 * 22.99 g/mol) + 32.07 g/mol + (4 * 16.00 g/mol) = 142.04 g/mol
- Molar mass of 10H2O = (10 * 2 * 1.01 g/mol) + (10 * 16.00 g/mol) = 180.18 g/mol
Now, you can sum the molar masses together to calculate the molar mass of Na2SO4·10H2O:
Molar mass of Na2SO4·10H2O = 142.04 g/mol + 180.18 g/mol = 322.22 g/mol
The mass of Na2SO4·10H2O needed can be calculated using the equation:
mass = moles * molar mass
mass of Na2SO4·10H2O = 0.0125 moles * 322.22 g/mol = 4.028 g
Therefore, to make a 500 mL solution that is 0.025 M in sulfate anion, you would need approximately 4.028 grams of sodium sulfate decahydrate.